Download Chapter 3 CHARACTERISTICS OF LEAD

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MINISTRY OF EDUCATION AND TRAINING
HANOI UNIVERSITY OF MINING AND GEOLOGY
DAO THAI BAC
STUDY ON CHARACTERISTICS AND
DISTRIBUTION REGULARITIES
OF LEAD-ZINC METALLOGENIC FORMATIONS
IN THE VIET BAC AREA
Specialization: Mineral Resources
Code No.: 62.44.59.01
ABSTRACT OF THESIS
OF DOCTORATE IN GEOLOGY
HA NOI -2011
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Research finished at: Department of Mineral Resources, Faculty of Geology
Hanoi University of Mining and Geology
Supervisors:
1. Assoc. Prof. Nguyen Quang Luat;
2. Assoc. Prof. Pham Van Truong.
Reviewer 1:
Reviewer 2:
Reviewer 3:
This thesis is going to be defended at the council of doctorate thesis examiners of
Hanoi University of Mining and Geology
(Dong Ngac commune, Tu Liem district, Hanoi)
On ……Date……
This thesis can be found at: - Vietnamese National Library
- Library of Hanoi University of Mining and Geology
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PREFACE
1. Necessary requirement of research
Viet Bac area is featured by a really complicated geologiacal structure and variety
of mineral deposit, in that lead-zinc ore with wealthy of types, quality and reserves,
considered one of major mineral resource. The results of investigation, prospection and
exploration so far discovered 140 lead-zinc deposits with different sizes, many of them
have been explored and put into exploitation and some of them have been exploited
since French colonial times. The fact that these mines are at risk to empty out calls to
discover new lead-zinc deposits to supply this important substance for development of
national industry.
The previous investigative and research works have resolved some queries of
metallogenic theory and gotten certain practical significance. However, most of
published metallogenic research works was only studied the general regulatity of
endogenous mineral resources, some research on lead-zinc ore aim to research the
material compositions in details whilts not focus on conditions for the ore forming. In
fact, until now it has not been any study in the field of applied metallogeny.
In recent practice, one of the most difficult tasks is to assess the role of geological
formation in lead-zinc mineralization, thereby determining the premises and the ore
indicators in each area to get proper orientation for planning work of investigation,
estimation of the mineral resources and to find optimal prospecting method to discover
lead-zinc deposit. This is also an urgent requirement of practice.
2. Objectives
This thesis aims to clarify the characteristics of different types of lead-zinc
metallogenic formation and regualarity of their distribution in Viet Bac area, founding
a scientific basis oriented for the lead-zinc ore prospection and exploration in study
area from the point of view of applied metallogeny.
3. Study subjects of thesis
This thesis focuses on lead-zinc deposits and occurences and the geological
formations involved in the Viet Bac area.
4. The research scope of thesis
Viet Bac is located in Northeastern region of Vietnam. It is bounded by Song
Chay fault to the west-south-west; by Song Thuong fault to the south-east, by ChinaVietnam boundary to the north and northeastern. The region’s area is about
30.000km2.
5. The task of the thesis:
To achieve its objectives, the thesis has been designed to work on main tasks as
follows:
- Selectively collect, codify and integrate documents, researched results on
geology and lead-zinc mineral resource in the study area, as well as other relevant
published in the country and the world documents;
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- Study lead-zinc ore material composition and the forming geological
characteristics thereby determine existed lead-zinc ore formations in the study area;
- Assess the role of the geological formations for lead-zinc ore forming process;
- Define types of lead-zinc metallogenic formation; clarify of their distribution
regularities;
- Determine ore control factors, premises of mineralization and ore indicators
for prospection and estimation of lead-zinc ore perspective in the study area.
6. Research methods
The thesis is built on the basis of using traditional research methods combined
with modern research methods as follows:
- Method of collectiong and codifying documents and data;
- Combination of research methods in the field work;
- Combination of methods studying material composition of rocks and ores (ore
chemical analysis, atomic absort spectro, mineralography, petrographic thin section...);
- Method studying the role of geological formation in ore-forming process and
analyzing the types of metallogenic formation;
- Method studying ore-forming condition by using isotopic analysis;
- Geochemical method;
- Geophysical method;
- Computing method;
- Combination of documental analyzing, processing, comparing and compiling methods.
7. New scientific-significant outcomes of the thesis
- Identify and assess the significances and roles of the geological formations for
the lead-zinc mineralization in the study area, among that the rocks belonging Pia
Phuong (D1pp) and Tong Ba (D1tb) formations with the stratiform ore body plays an
important role for the lead-zinc mineralization in the Viet Bac area.
- Establish and define the three types of metallogenic formation (TMF) of lead-zinc
mineralization in the Viet Bac area, including TVQ=TMQ, (TVQ=TMQ) + (TTQ=TSQ)
and TVQ+TSQ TMF type; clarify their distribution regularites in space and time.
- Through applying of metallogenic research of lead-zinc metallogeny in the Viet
Bac area as a new approach - the notion of “Applied Metalogeny”, it is pointed out the
problems to be further research: the relationship between magmatism with Lead-zinc
mineralization in study area and detaled study on the lead-zinc deposit model with
veint form ore bodies beside stratiform ore bodies.
8. Scientific and practical significances of thesis
8.1 Sientific significances
- This thesis could make itself a reference for assessing the role of geological
formations in lead-zinc ore-forming process when study lead-zinc mineralization using
applied metallogeny.
- This thesis has determined the general regularities of lead-zinc metallogeny in
Viet Bac area from the point of view of applied metallogeny. These regularities could
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be used to study lead-zinc mineralization in other regions with similar geological
characteristics.
8.2. Practical significances
- This work has determined premises and ore guide for prospecting that gives
guidance for exploration of lead-zinc ores.
- It contributes to clarify the regularities of distribution and to delineate the areas
of different perspective of lead-zinc ore, thus gives scientific basis for planning
investigation of lead-zinc minerals in the Viet Bac area.
- It also contributes to reassess lead-zinc ore scale and perspective in order to set
up appropriate investment strategies for investigation and estimation.
9. Arguments of the thesis
Argument 1: There are three types of lead-zinc metallogenic formation: TVQ =
TMQ, (TVQ = TMQ) + (TTQ = TSQ) and TVQ + TSQ in Viet Bac area; each type is
characterized by a group of lead-zinc ore formations distributed in different geological
formations of Paleozoic or Mesozoic ages.
Argument 2: Every type of metallogenic formation in Viet Bac area is closely
related to certain lithotectonic assemblages with prominent lithotectonic assemblages
are lithotectonic assemblage of Devonian-Permian passive continental margin,
lithotectonic assemblage of Late Permian-Triassic sedimentary and volcanic-plutonic
intracontinental rift, and lithotectonic assemblage of Mid-Late Triassic subcontinental
and continental molasses.
10. Content of thesis
The content of thesis, except Introduction and Conclusion, consists of 5 chapters:
Chapter 1. Characteristics of geological structure in Viet Bac area
Chapter 2. Basis of theory and research methodology
Chapter 3. Characteristics of lead-zinc mineralization in the Viet Bac area
Chapter 4. Role of geological formations in ore-forming process and the types of leadzinc metallogenic formation in the Viet Bac area.
Chapter 5. Distribution regularities of types of lead-zinc metallogenic formations in
Viet Bac area.
11. Background data and documents for this thesis
The thesis was completed on the basis of factual data and documents and research
results on lead-zinc that author collected since 1994 to present. Author has been
processed and compiled data from 400 ore polish samples, 300 thin section samples, 600
samples for ore chemical analysis, 250 samples for atomic absorption spectro analysis,
150 Au and Ag fire assaying samples, 50 fluid inclusion researching samples, 300 ICP
samples, 61 Pb and S isotopic analysing samples, 50 microzond samples and 50 neutron
activating samples.
Background materials for this thesis also include data collected by PhD student
from geological and mineral reports, previous research works on metallogeny from
Geological Archives, documents on lead-zinc ore-forming that have published in national
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and international professional journals, books, papers, theses of different authors on leadzinc ore-forming and reference resources from internet.
12. Acknowledgments
The thesis was completed at the Department of Mineral Resources, Faculty of
Geology, Hanoi University of Mining and Geology under direct supervision of
Associate Professor - PhD of Geography-Geology Nguyen Quang Luat and Associate
Professor - PhD of Geology-Mineralogy Pham Van Truong.
In the process of completing a thesis, PhD-student has been extremely fortunate
to receive the generous support of a wide range of Board of Leaders of Hanoi
University of Mining and Geology; Department of Post-graduate Training ;
Leadership of the Department of Geology and Minerals of Vietnam; Leadership of
Center for Information and Archives of Geology. PhD-student has also thankfully
received advice, insights, resources and practical assistance as well as specialised
skills and knowledge sharing from PhD Tran Dinh Sam, PhD Pham Dinh Tho, PhD
Tran Van Mien, PhD Nguyen Van Binh, PhD Bui Tat Hop, PhD Tran Tuan Anh, and
many other scientists and colleagues.
I would like to express deeply thanks to the leaderships of institutions, scientics
and individuals mentioned above for their great help and support.
THE CONTAINT OF THESIS
Chapter 1
CHARACTERISTICS OF GEOLOGICAL STRUCTURE IN VIET BAC AREA
1.1. The location study areas in the scheme of regional structures
In the the present scheme of structure, Viet Bac are located in the region of
early Neoproterozoic-early Mesozoic multiperiodic orogenic system including Early
Paleozoic intracontinental orogenic belts and Late Paleozoic-Cenozoic intracontinental
basins with Late Paleozoic-Cenozoic intracontinental rift system and is divided into
the major tectonic units: the early Paleozoic intracontinental orogenic belts (including
western Viet Bac and eastern Bac Bo orogenic belts); the Song Hien late PaleozoicCenozoic intracontinental basin.
1.2. History of geological and mineral resources research
History of geological and mineral resources research in Northern Vietnam,
particularly in the Viet Bac Area, was divided into two periods:
1.2.1. Period before 1954: The regional research work, appeared since French
colonial times, but it only highlighted the sketchy features of the geological profile of
Indochina. The prospection and exploration of mineral resourses not systemic, just for
temporary exploitation purposes, and left documents is very poor.
1.2.2. Period after 1954: Starting with the establishment of the geological map of
North Vietnam of l: 500,000 scale (Dovjikov AE et al., 1963), in which the North
Vietnamese are classified into Northeast Vietnam Nam standard folding system.
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In the following year, geological mapping works at 1:200.00 scale were
conducted in a systematic way; many ore deposits was discovered and investigated.
The geological mapping and regional prospecting for mineral works of 1:50.000 scale
had covered approximately 70% of study area, among that many mineral occurrences
have been investigated in details at scale 1:10.000.
The study of metallogy starting to be deployed with the launch of the project:
"The lead-zinc ore formation of Viet Bac domain" of Vu Ngoc Hai (1976),
"Conditions for the distribution of lead-zinc ore and North Vietnamese and
prospecting orientation” (Nguyen Huy Sinh)," Basic characteristics of endogenous
main ore formations in Northern Vietnam" by Nguyen Van Chu et al (1981)," Lo Gam
zone mineralization rate of 1 : 1,000,000" (Thai Quy Lam, Vu Ngoc Hai, 1990) ... and
some other single study.
Tasks of mineral propspecting, assessement and exploration have early developed
since 1960s at lead-zince ore deposits, which were quite famous at French colonial
time such as Cho Dien, Lang Hit and Mo Ba mines, and are increasingly promoting.
These works have resulted in a huge volume of data and documents about lead-zince ore
of Viet Bac area with high significance for reference and serving for exploitation.
However, of the above mentioned works, there has not any study been completed
based on the viewpoint of applied metallogy. This desertation will be conducted with
this point of view.
1.3. General stratigraphy
Geological structure of the Viet Bac area is composed by geological formations
of Neoproterozoic- Early Cambrian to Quaternary ages.
Neoproterozoic- Lower Cambrian formations: include Thac Ba formation (NPε1tb), An Phu formation (N3-ε1 ap) with memorphic rocks.
Cambrian formations: include Ha Giang formation (ε2hg), Mo Dong formation
(ε2mđ), Than Sa formation (ε3ts) and Chang Pung formation (ε3cp), which are composed
of metamorphic terrigene sediment altenated with carbonate sediment (Quartzite,
quartzitic sandstone, shist, limestone, marble, etc.)
Ordovician and Ordovician – Silur formations: include Lutxia formation (O1lx),
Na Mo formation (O2-3 nm) and Phu Ngu (O3-S2pn) which are composed of terigenous
sediment interbeded lenses of limestone.
Devon formations: include formations of D1 to D3 ages.
D1 aged formations: include Tong Ba formation (D1tb), Pia Phuong formation
(D1pp), Song Cau formation (D1sc), Mia Le formation (D1ml), which are characterized
by Carbonate-terrigene sediments (terrigene alternated with carbonate sediments as
appeared in Tong Ba formation)
D1-2 aged formations: include Khao Loc (D1-2kl) and Na Quan (D1-2nq), which are
composed of terrigene alternated with carbonate sediments.
D2-3 aged formations: include Tam Hoa formation (D2-3 th) and Toc Tat (D3tt)
Tam Hoa formation (D2-3 th) is composed of conglomerate, shist and limestone
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Toc Tat formation (D3tt) is composed of stripped limestone, silicious limestone,
manganeous silicious shist.
Carbon– Permian formations: include Bac Son formation (C-Pbs), Dong Dang
(P2đđ) which are characterized by massive limestone (C-Pbs) and bauxitic limestone,
silicious shale (P2đđ).
Triassic formations: include formations of T1 to T3 ages.
T1 aged formations: include Lang Son formation (T1ls), Hong Ngai formation
(T1hn) and Song Hien formation (T1sh), which are composed of terrigene sediment
(T1ls), cherty carbonate sediment (T1hn) and terrigene sediment alternated with
effusive rhyolit (T1sh).
T2 aged formations: include Tam Dao formation (T2tđ) which is composed of acid
effusive rock, Lan Pang formation (T2lp) with transition from terrigene sediment upto
carbonate, Khon Lang formation (T2kl) with clastic sediment alternated with effusive
layers and Na Khuat (T2nk) with carbonate bearing sandstone-siltstone.
T3 aged formations: include Van Lang formation (T3vl) and Mau Son formation (T3ms)
Jurassic-Cretaceous formations: include Ha Coi formation (J1-2hc) with red
continental sediment, Tam Lung formation (J3tl) with terrigene sediment intercalated with
subalkalic effusive rock and Ban Hang formation (Kbh) with continental sediment.
Neogenic formations: include Na Duong formation (N1nd) with coal -bearing
continental sediment.
Quaternary formations: include modern unsoncolidated sediments.
1.4. Overview of magmatic intrusion activities
Within the study area, there appear the following magmatic complexes:
A. Late Neoproterozoic - Middle Paleozoic magmatic complexes
A.1. Ophiolite assemblages in orogenetic structure
1. Metabasalt in Ha Giang formation (2hg)
2. Nam But ultramafic complex (PZ1nb)
3. Bach Sa complex (pγvμPZ1bx)
A.2. Granitoid in the intracontinetal orogenic structures of Bac Bo
1. Song Chay granitoid complex (γPZ1-2sc):
2. Phia Ma alkalic granitoid complex (γDpm):
3. Alkali-felsic volcanic-plutonic roks in Tong Ba area (γD1tb):
B. Late Paleozoic-early Mesozoic magmatic complexes
B.1. Permian-Triassic volcanic-plutonic assemblages in intracontinental rift
systems of Bac Bo
1. Bang Giang mafic volcanic complex (vP3-T1bg):
2. Cao Bang gabbro-peridotit complex (vP3cb):
3. Felsic volcanic rorks of Song Hien formation (T1sh).
4. Nui Dieng granite granophyre complex (T1nđ):
B.2. Mafic-ultramafic intrusions
1. Nui Chua gabbro-peridotit complex (vP3-T1nc):
2. Phia Bioc aluminium-rich granite complex (γP3-Tpb).
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3. Luc Yen-Cho Don gabbro-syenite complex (γξT2lc):
C. Late Mesozoic aluminium-rich granite in intraplate structure.
Pia Oac aluminum-rich granite complex (γK2 po).
1.5. Overview of tectonic structure
A. TECTONIC UNITS AND LITHOTECTONIC ASSEMBLAGE
1. East Bac Bo early Paleozoic intracontinental orogenic belt
1. West Viet Bac zone
a) Lo river sub-zone
- Meso-Neoproterozoic hight grade metamorphic lithotectonic assemblage
- Early late Neoproterozoic-Ordovician passive continental margin lithotectonic
assemblage
- Early Neoproterozoic-Paleozoic ophiolite lithotectonic assemblage
- Mid Ordocician-Silurian intracontinental lithotectonic assemblage
- lithotectonic assemblage of Devonian intracontinental rift type
b) Gam river sub-zone
- Lithotectonic assemglage of late Neoproterozoic-early Paleozoic passive
continental shelf.
- Neoproterozoic-early Cambrian hight-grade metamorphic lithotectonic assemblage.
- Lithotectonic assemglage of Mid Cambrian-Ordovician-Silurian passive continental margin.
- Lithotectonic assemglage of Devonian-Permian passive continental shelf: includes 2 series:
- Devon serie, which covers the Low Ordovian sediment.
- Carbon-Permian sediment
2. Northeast Bac Bo zone
- Lithotectonic assemblages of Cambrian-Silurian passive continental shelf of
aulacogenic type
- Lithotectonic assemblages of Devonian-Permian passive continental shelf
include 2 series:
Devon- Low Carbon serie
Carbon-Middle Permian serie
2. Late Paleozoic -Cennozoic intracontinental basin structures
- Lithotectonic assemblages of Late Permian-Triassic sedimentary and volcanicplutonic intraontinental rift - Assemblage of Mid-Late Triassic subcontinental,
continental molasse
- Assemblage of Noric-Jurassic molasse
B. MAJOR FAULTS ZONE
- Cao Bang-Tien Yen fault zone
- Yen Minh-Ngan Son fault zone
- Ha Giang-Ba Be-Son Duong fault zone
- Bac Quang-Na Sai fault zone
- Song Day fault zone
- Song Lo fault zone
- Song Thuong fault zone
- Song Chay fault zone
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Chapter 2
BASIS OF THEORY AND RESEARCHING METHODOLOGY
2.1. Geochemical and mineralogical characteristics of lead and zinc
2.1.1. Geochemical characteristics of lead and zinc
Lead - abbreviated as Pb, is element referred to Group IV, Mendeleev periodic table,
order number of element is 82. In nature Pb primarily seen in the form of chemotherapy Pb+2
with four stable isotopes (204Pb, 206Pb, 207Pb and 208Pb), most of which is 208 Pb.
The average grade of Pb in the Earth's crust (the value Clarke as Vinagradov A. E) is
16ppm (1,6.10-3%). Secondary compounds of Pb in the exogenous zones is the durable
compound, have low solubility, less movement, often stay in place or position not far from
the initial buildup.
Zinc is denoted by Zn and chemical numbers is 30, in the wild has four stable isotopes
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Zn , Zn66, Zn67, Zn68 with Zn64 is the most common. The average grade of zinc in the Earth's
crust (the value of Clarke as Vinagradov A. E.) is 83ppm (8.3.10-3%); coefficient of
concentration of Zn is 500.
Pb and Zn are chalcofile elements, which are generally paragenetic in
endogenous conditions and concentrated mainly in hydrothermal vein, forming
compounds with sulfur, especially in moderate-temperature hydrothermal vein, there
may be having paragenitic Cu-Pb-Zn in the mineral association chalcopyritesphalerite-galena. In exogenous conditions, due to solubility of Zn is many times
greater than Pb, they often separated from one another.
2.1.2. Mineralogical characteristics of lead and zinc
So far has discovered 144 minerals containing Pb and 58 minerals containing Zn
but in which only a few are valuable industrial minerals.
The major minerals of lead ore is galena (PbS), followed are bournonite
(PbCuSbS3), boulangerite (Pb5Sb4S11), jamesonite (Pb4FeSb6S14), cerussite (PbCO3),
anglesite (PbSO4), pyromorphite(Pb5[PO4]4Cl).
The major minerals of zinc ore is (ZnS), followed are wurtzite (ZnS), smithsonite
(ZnCO3), calamine (Zn4[Si2O7](OH)2.H2O), zincite (ZnO2), hydrozincite (Zn5
(OH)6[CO3]2).
Among above minerals, sphalerite and galena are major ore minerals in the
sulfide lead-zinc ore bodies. In oxidizing environment the ore bodies are usually
altered into the oxide ore body with the typical minerals of lead and zinc in the
oxidation zone: cerussite, anglesite, smithsonite, calamine, zincite...
2.2 The basic concepts used in the thesis
2.2.1. The concept of research the characteristics of ore and mineral deposits
- Ore formation: according to Konstantinov R. M., 1973, the ore formation are
assemblage of mineral deposits with sustainable paragenetic mineral associations
similar in composition, was formed in close geological setting
- Ore type: One type of ore formation may have one or more ore-forming stages
matching to the different paragenetic mineral associations, they form the typical ore
types for each stage.
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2.2.2. The concept of the role of geological formations in mineraliztion and
metallogenic formation of mineralization.
- Ore-hosted formation (TVQ): are geological formations, playing role of geological
environment acts as a passive ore accumulation, in which elements of ore-forming
process such as the material source and transport agents are related to the different
geological formations.
- Ore-bearing formation (TMQ): As the geological formations, when were
formed carrying a certain amount of ore material. Ore-bearing formation may be
environment of ore deposits when the ore material in it enough to accumulate into the
ore body or they are mobilized and re-concentrated by energy of other geological
formations, ore-bearing formations may also refer to the ore material source of the
other ore-forming processes.
- Ore-genetic formation (TSQ): As the geological formations, act as a source of
material, energy and migration agent for the ore product located in the ore
accumulative environment (in TVQ).
- Ore-forming formation (TTQ): As the geological formations, act as a source of
energy to mobilize and re-deposition of the ore material contained in the other
geological ore-bearing formation (in TMQ).
In the ore-forming process, it’s often a combination of two or more geological
formations with different roles; in this case, to denote the combination the "+" sign is used
between the geological formations. Also, a geological formations can play two or three
different roles in the ore-forming process; to denote this case the abbreviation symbol of
the geological formations is put in brackets and is connected together by a "=".
The combination of geological formations with different roles in ore-forming
process create a combination reflect the ore accumulation model and determine the
type of metallogenic formation.
Metallogenic formation: As a often observed sustained space-time paragenetic
combination of the geological formation, metasomatic formation and ore formation
(Krivsov A.I., 1989).
Based on the most common ore-forming model and types of ore-forming process,
A.I. Krivxov (1989) divided into six types of metallogenic formations (THSK):
- Metallogenic formation of TVQ + TSQ type: as combining the corresponding
classic diagram of genegis of the formation of hydrothermal veinform deposits,
located in the geological formations with different properties with stability of
properties of ore formation and stable space-time association with magmatic
complexes of the same type of ore-hosting formation (TSQ).
- Metallogenic formation of TVQ=TMQ type: The same formation involved two
roles - typical for a first series of deposits is the stratiform deposits and deposits close
to them. This situation is typical for deposits of copper-bearing sandstone and copper
slate types, lead-zinc deposits in terrigene-carbonate and carbonate layers.
Metallogenic formation of TVQ=TMQ=TSQ type: This combination is typical
for the ore-forming processes to be fully unified into a single formation.
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Metallogenic formation of TVQ + (TVQ=TMQ=TSQ) type: This combination
is close to the type TVQ + TSQ, but differs in that one of formation plays three roles.
Corresponding to this combination is the mixed ore-forming model, the ore
mineralization in which is located in magmatic intrusions of the same type formation
(TVQ=TMQ=TSQ) and in passively ore-hosted geological formations of any
component along the edge (TVQ).
Metallogenic formation of (TVQ=TMQ) + TTQ type: Combining the two
formations, reflecting the ore-forming model, the ore accumulation in which is related
with redistribution of material in the TVQ = TMQ formation of the same type, under
the action of heat and fluid of later appeared magmatic intrusions (TTQ) with distinct
formation attribute.
Metallogenic formation (TVQ=TMQ) + (TTQ=TSQ) type: Combining different
from above type by the participation of the material, derived from two formations and
placed on the hydrothermal-metamorphic ore-forming model as well as some
polygenetic deposits, and in particular iron deposit and skarn polymetallic deposits.
2.3. Classification of lead-zinc deposits in the world and in Vietnam
2.3.1. Classification of lead-zinc deposits in the world
So far there is still no consensus still no general consensus on the classification of leadzinc mine. Overall, there are two aims of classification theory: the aim of Soviet scientists
and the aim of the West scientists (Table 2.1). Specifically, each aim also has many different
types of classification.
Table 2.1: Comparing the classification of genenic types of lead-zinc deposits
in two types represent different tendency.
Old Soviet scientists aim
Smirnov V.I, Ginzburg A.I, Grigirev B. M,
Iacovlev G.F (1982)
1. Skarn lead-zinc deposits:
Galena-sphalerite formation
2. Plutonic-hydrothermal lead-zinc deposit:
1) Metasomatic pyrite-galena-sphalerite formation in
carbonate rock;
2) Veinform galena-sphalerite formation in
granitoid rock and shist.
West scientists aim
Eckstrand O.R. (1984), Roberts R.G. and Sheahan, P.A. (1988), Trygve Hõy, V.
Kirkha, Sinclair, Thorpe and Duke, Ray G. E, Church B. N, Kula C. Misra,
Ryan D. Taylor, D. V. Lefebure, Leach D. L. and Sangster D. F (1993, 1995,
1996); Trueman E.A (1998), J.L. Nelson, A. Fonseca and G. Bradshaw (2005)...
Syngenetic
1. VMS type:
- Noranda/Kuroko type
- Cyprus type
- Besshi type: Cu, Zn, Pb,
Ag (Au, Co, Sn, Mo, Cd).
3. Volcanic hydrothermal lead-zinc deposit:
Chalcopyrite-sphalerite-galena formation in volcanic
rock
6. Metamorphic lead-zinc deposit (Broken-Hill,
Sulivan): 1) Pyrhotine-pyrite-sphalerite-galenite
formation in carbonate metamorphic rock; 2)
Galena-sphalerite-pyrhotine-pyrite formation in
siliceous metamorphic rock.
3. Carbonate hosted Pb-Znc ore deposits
- Tsumeb /Kipushi type: Cu, Pb, Zn, Ge
(Ag, Ga, As, Cd)
- Irish type: Zn, Pb, Ag (Cu, Ba, Cd)
- Mississippi Valey type (MTV): Cu, Pb,
Zn, Ge (Ag, Ga, As, Cd)
4. Skarn Pb-Zn deposit: Pb, Zn, Ag,
(Cu, Cd, W, Au)
4. Stratiform lead-zinc deposit (Missisipi-Misuri):
lead-zinc-barite formation in carbonate rock
5. Colchedan lead-zinc deposit::1) Chalcopyritegalena-sphalerite-pyrite formation; 2) galenasphalerite-pyrite formation
Epigenetic
2. Sedex type: Broken Hilltype (BHT): Pb, Zn, Ag
(Cu, Au, barit)

5. Polymetalic Mantos: Sn (Cu, Zn, Pb,
Ag, Sb, Cd, Bi, In).
6. Polymetalic vein Ag-Pb-Zn: Ag, Pb,
Zn (Cu, Au, Mn).
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2.3.2. Classification of lead-zinc deposits in Viet Nam
In Vietnam, many authors have also studied, classificated the lead-zinc deposits,
mainly based on the following criteria:
+ Composition of ore material (in which the mineral composition is important)
+ Characteristics of host rock
+ Features of ore-forming genegis
2.4. Research methods using in the thesis
2.4.1. Document compiling: The material collected in the thesis includes the tectonic,
magmatic documents and documents on ore composition. Results of the collection,
analysis and compiling of materials has helped thesis provides some important
observations and conclusions.
2.4.2. Field work survey and study: Field work has the task to check the compiled data
take more samples for needed analysis... to clarify or confirm some outstanding issues.
Athor of thesis have conducted a survey in two areas: Cho Don and Na Son, took
some rock and ore samples for additional analysis.
2.4.3. The analytical methods: The analytical methods were applied to the thesis, among that
the major is mineralographical analysis in which 150 ore polish samples has been carried on.
2.4.4. Method studying the ore material composition: mainly to study the material
composition and ore structural, textural characteristics to make the conclusion about
the ore-forming mode, to help identify the deposit genensis.
2.4.5. Method studying the role of geological formation in ore-forming process and
analyzing the types of metallogenic formation: The analysis and assess the role of the
geological formation geology for ore-forming process thereby establishing a
metallogenic formation.
2.4.6. Geochemical method: Identification of geochemical anomalies of ore element.
2.4.7. Geophysical method: Determination of the geophysical anomalies that related to
mineralization.
2.4.8. Computing method: Statistical processing of the samples; Integrate data;
overlayering information to compare the different objects.
Chapter 3
CHARACTERISTICS OF LEAD-ZINC MINERALIZATION
IN THE VIET BAC AREA
The lead-zinc deposits the Viet Bac area are classified into four types of ore system below:
1 - The lead-zinc ore formation in carbonate-terrigene sedimentary alternated
volcanic and sub volcanic formations.
2 - The lead-zinc ore formation in carbonate sedimentary formations.
3 - The veinform lead-zinc ore formation (thin bearing) in carbonate-terrigene
sedimentary formations.
4 - The veinform lead-zinc ore formation in terrigene sedimentary and terrigeneeffusive formations of MZ age.
12
3.1. The lead-zinc ore formation in carbonate-terrigene sedimentary
alternated volcanic and sub volcanic formations (included 2 ore types)
3.1.1. The sphalerite-pyrite-galena-chalcopyrite ore type (Na Son type)
It includes Na Son, Ha Vinh, Sang Than, Ta Pan, Suoi Thau, Ban Kep,…deposits
and occurrences, distributed in Tong Ba-Bac Me range (Ha Giang), also called " Tong
Ba - Bac Me tectonic gutter". The rocks in the area in a relatively complicate was
disturbed and metamorphosed, until now there has never been consensus: Vuong
Manh Son et al (2003), has classified above rocks into Ban Cuom formation, which
are not certified effusive components although many works before and after him has
confirmed the presence of trachyt, ryolit.
Characteristics of distribution and morphology of orebodies of deposits,
occurrences in this geological formation have importante features as follow:
- The locations of ore accumulation: Lead-zinc ore zone tend to be concentrated
in the calcite quartz schist, metamorphosed calcareous shale (Ta Pan, zone I-NaSon),
or in edge zone of Tong Ba subvolcanic complex (zone II-Na Son).
- The lead-zinc orebodies were concentrated in roof part of intrusion of Tong Ba
subvolcanic granitoid complex.
- The rich orebodies of large-scale often distributed in carbonaceous shist or
limestone, marble.
- Morphology of ore bodies: the lead-zinc ore bodies is stratiform, conformable with
host rock (ore zone I of Na Son deposits, Ta pan and Suoi Thau deposits) and were
controlled mainly by petrostratigraphic factor. Besides that it is also the vein form, lense
form ore bodies distributed in differente rocks or in subvolcanic rock (ore zone II of Na
Son deposits) and were controlled mainly by tectonic and structural factors.
- There is a companionship of the iron ore body and polymetallic sulfide ore body
with clear order in sections: in lower part bedded iron ore body, upper part are pyritepyrrhotite and lead-zinc ore bodies. At some deposits there are also barite ore bodies
accompanying together with lead-zinc ore bodies.
- Most of the ore bodies accompanied by hydrothermal alterations with varying grades
which popular are quartzitization, calcitization, dolomitization and sericitization.
In deposits of this type, some deposits have been quite extensively studied on
material composition, typical is Na Son deposit.
The ore chemical components: Major elements are Pb, Zn; associated useful
elements include Ag, Cd, Sb, Bi, Mo, In, Ge, Tl, Se, Te.
The ore mineral components: The common primary ore minerals are sphalerite,
galena, chalcopyrite, pyrite, magnetite and pyrrhotite. More rarly are magnetite,
tetrahedrite; the major secondary minerals are including of goethite, anglesite, covelline,
smithsonite, cerussite, melnicovite; guange minerals are: quartz, calcite and dolomite.
The typical ore mineral association: quartz-galena-sphalerite-chalcopyrite
13
Based on mineral composition and the relationship between the ore minerals, the
paragenesic mineral association in two zone of Na Son lead-zinc deposits can be
classified as follows:
Zone I includes 3 associations: 1) Quartz-magnetite-pyrite-pyrrhotite; 2) Sphaleritegalena-pyrite-pyrrhotite-chalcopyrite; 3) Galenite-sphalerite-pyrite-chalcopyrite.
Zone I includes 3 associations: 1) Galena-sphalerite-pyrite-chalcopyrite; 2) Galenasphalerite-pyrite- chalcopyrite-tetrahedrite, argentite; 3) Quartz-galenite-sphalerite.
The orre-forming stages:
- The stage I: quartz - magnetite - hematite – pyrite.
- The stage II: sphalerite - galena - pyrite.
- The stage III: galena-sphalerite-pyrite-chalcopyrite…- tetrahedrite, argentite and
it was lead-zinc ore productive stage of ore zone II.
Regarding genesis of Na Son deposit: Nguyen Van Nhan (1985) classified it into
effusive hydrothermal type; Dinh Van Dien (1984) classified into colchedan type; Tran
Anh Ngoan (1988) classified into subvolcanic hydrothermal type, many geologists asumed
that Na Son deposit is metasomatic hydrothermal deposit. Ratkin V.V, Tran Van Duong
(1983, 1989, 1991) has concluded that this deposit is multi-periodic polygenetic type.
3.1.2. The galena-sphalerite-silver ore type (Ban Lin type)
Under this type include the deposits, occurrences distributed in the Ban Lin-Lung
Thom, Phia Dam-Bang thanh, Khuoi Man-Bang Thanh areas..... Previously many
geologists are classified in Na Son type, but recent studies of Do Quoc Binh (2005,
2009) show that in these deposits it is mainly zinc-barite-silver ore of stratiform type
beded in carbonate-terrigene sediments alternated acid effusive rock. There is also the
lead-zinc mineralization in hydrothermal but small scale quartz vein.
The major ore mineral components are barite, sphalerite, galena and pyrite. These
minerals exist as fine grains disseminated in the dolomite limestone.
Ore has regular disseminated or banded structures dolomite layers. Pinch the ore
body is lenticular in the rock layers containing mineralization. Ore has common fine
granular, pseudomorphic replacemental teztures. The minerals infected in rock
background in banded form.
Based on morphological characteristics, characteristics of the geological structure
and forming environment, ore material composition, distribution and characteristics of
the hosted rock, characteristics of stable isotopes of sulfur S34… Do Quoc Binh
identified that these deposits and occurrences had hydrothermal-sedimentary genegis
of SEDEX type.
3.2. The lead-zinc ore formation in carbonate sedimentary formations
(include 3 ore types)
3.2.1. The sphalerite-galena-pyrite ore type (Cho Dien type)
Typical are the deposits in Cho Dien, Cho Don, Tuyen Quang ..., among that
deposits in Cho Don and Cho Dien region were the most studied. Lead-zinc ore
bearing fold structure in Cho Don - Cho Dien are Phi Khao brachyanticline, axis of
14
which is extended to north northwest-south southeast direction. Composant of this
anticline are carbonate and carbonate-terrigene sediments of Late Devonian age of Pia
Phuong and Mia Le formations. Popular magmatic activities were rich-aluminium
granite, syenite and sometimes have found the maffic-gabbrodolerite dykes.
The fault systems in the area played a ore-control role and were the factors which
shifted, complicated ore bodies.
The morphology of ore bodies in the both areas is quite diverse and complicate
and there is interdigitation with each other of types: The ore bodies are in the vein
form, infilled the faults or cleavage zones, and stratiform, almost conformable with
carbonate host rocks
Composition of ore material in the two areas was similar in both chemical
component and mineral component.
The ore was formed in 3 major stages (Table 3.11):
- Stage 1: Typical paragenetic mineral association is quartz-arsenopyrite-pyrite.
- Stage 2: Typical paragenetic mineral association is galena-sphalerite-pyrite.
- Stage 3: Typical paragenetic mineral association is quartz-calcite-pyrite.
15
Table 3.11: The order of ore-forming and paragenetic mineral association
of Na Bop lead-zinc deposit, Cho Don
Ore-forming
period
Ore-forming
stage
Paragenetic
mineral
association
Quartz
Dolomite
Calcite
Calcedone
Sericite
Chlorite
Pyrite
Arsenopyrite
Pyrrhotite
Hydrothermal
Epigenetics (Exogenous)
I
II
III
IV
V
Quartz-pyrite arsenopyritepyrrhotite
Galena sphaleritepyrite
Calcite-quartzpyrite
Anglesitecerussitesmithsonite
Goethitehyđrogoethite
Sphalerite
Galena
Chalcopyrite
Cassiterite
Argentite
Pyragyrite
Tetrahedrite
Tennatite
Marcasite
Specularite
Anglesite
Cerussite
Smithsonit
Bornite
Scorodite
Pyrolusite
Hydrohematite
Hydrogoethite
Goethite
Si, Fe, O, S, As,
Zn, Pb, Cu, Sn,
Ca, Mg.
Si, O, S, Fe, As,
Zn, Pb, Cu, Ca,
Mg, Ag, Sb.
Typical ore
structures
Nest, vein,
disseminated
Disseminated,
massive, vein
Typical ore
textures
Allomorphicgranular,
cataclasic
Idiomorphicgranular,
allomorphicgranular, ìnfilled
Dolomitization
Dolomitization,
sericitization,
chloritization,
epidotization.
Typical elements
Hydrothermal
alterations
Notes:
Primary min.;
Secondary min.;
Si, O, Fe, S, Ca.
vein,
disseminated,
nest
Idiomorphicgranular,
allomorphicgranular,
colloidal
Fe, Mn,Pb,
S, Cu, Fe, O,
Zn,CO2, O,
As, CO2, SO4.
OH
Colloidal,
Nest, vein
pore,
stockwork
microgranular,
pseudomorph,
colloidal,
aureole, halo ,
cryptocrystalli
rim, colloidal
ne
Calcitization
Rare min.;
Min. of disintegration of solid solution
16
3.2.2. The sphalerite-galena ore type (Lang Hit type)
Representatives for this type are the Lang Hit, Con Minh, Coc Keng, Trang Da…
deposits. Lead-zinc mineralization sometimes contain barite, usually being stratiform
bodies in carbonate rocks, sometime in crossing vein form, but always being
controlled in cabonat rocks.
The ore body types include: ore bodies formed by metasomatic mode, being any
shape; the stratiform ore bodies in the limestone; the vein ore bodies filled clefts,
faults. Host rocks were hydrothermally altered weakly: dolomitization, calcitization
The major ore elements: In Lang Hit, the major ore elements are Pb and Zn. The
rate of Pb/Zn ranged wide, in Metis ratio is 1/4, in Mo Ba is 1/6-20.
The associated elements: Most typical is Ag, concentrated in galena in
isomorphous mixture form. High concentration of Cd was also confirmed; in addition
it is also Ga; Ge and Sb.
The major ore mineral compnent are sphalerite, galena; more rarly are pyrite,
chalcopyrite, grey copper, pyrrhotite, arsenopyrite. The common guange minerals are
quartz, calcite, dolomite, barite and siderite.
The ore usually are massive, disseminated, brecciated structures with
allomorphic, infilling, cataclasic textures. Ore was formed in two stages:
- The first stage includes association of sphalerit minerals, pyrite, arsenopyrit,
pyrite, and quartz chalcopyrit.
- The next stage: galena, native copper, barite, calcite.
The presence of Sb, Ga and Ge with relatively high grade and low-grade Fe
within sphalerite reflects that the ore had been formed in low-temperature condition.
3.2.2. The galena-sphalerite-(barite) ore type (Luc Ba type)
The galena-sphalerite-barite ore type distributed along the Lo river, formed a
zone stretching from the Tuyen Quang town to Thuong Am (Son Duong) and Luc Ba
(Dai Tu). Mineralization is concentrated in carbonate rock of terrigene carbonate
formation of D1 age, mainly had been formed in regime of passive continental margin.
Typical for this ore type are Luc Ba deposit and deposits in Thuong Am.
* Luc Ba deposit belong Dai Tu district, Thai Nguyen province. The Lower
Devonian (D1) section includes: lower part are shist, siltstone alternated with
sandstone, siliceous rock, siliceous limestone, limestone; upper part are siltstone, shist
alternated with sandstone.
At pesent it‘s just seen a lead-zinc sulfide ore body. Ore body with 340 m long,
2.23 m thick, have been exploited since ancient times, extended to north-west, dipped
on the north-east with angle 60o. The grade of Pb 9,0%, Zn 1,12%, Ag 37,5g/T. The
ore mineral components are galena, sphalerite, barite, pyrite, less argentite; secondary
minerals are anglesite, smithsonite, mongeimite, goethite; guange minerals are quartz,
calcite and barite.
* The lead-zinc deposits in Thuong Am (Xom Phai, Khuon Lan, Y Nhan deposits)
Lead-zinc ore distributed and concentrated on the wing and southeast tip of the
anticline, in re-crystallized limestone of upper subformation, Pia Phuong formation.
Within edge surrounding the anticline zone distributed the barite occurrences (Ngai
Thang, Dong Ben ...).
17
The lead-zinc ore bodies are veinform, the lensform or stratiform. Some lead-zinc
ore bodies accompanied by barite ore bodies.
The ore chemical components are major ore elements Pb and Zn; associated
elements: Ag, Cd, As.
The lead-zinc ore in Thuong Am include typical paragenetic mineral associations,
matched 4 ore forming stages: 1. dolomite-chlorite; 2. Quartz II, pyrite II, arsenopyrite; 3.
Galena-sphalerite-chalcopyrite and 4. Quartz-calcite.
3.3. The veinform lead-zinc ore formation (bearing tin) in carbonateterrigene sedimentary formations
The deosits of this formation type are in close association with tin mineralization,
mostly developped in Bac Thai anticlinorium (Tran Van Tri, 1977). The mineralization
mainly distributed in areas such as domeform local uplift block in Ngan Son or Tong Tinh
(Pia Oac).
In Ngan Son, the mineralization mostly concentrated in calcareous shist, sericite
shist, bedding limestone, phylic sandstone of Mia Le formation (Dlml) that had
previously been classified into Coc Xo formation (D1-2cx). The presented magmatic rocks
in the area consist mainly of coarse to mid grain muscovite granite, two-mica. The
zonation of Pb-Zn mineralization around the granitoid intrusion is shown quite clearly: near
the granitoid intrusion ore are high Sn content (such as in Deng, Na Boc ...), further ore
consisting mainly of Pb, Zn (such as in Deo Gio, Phuc Son, Phuong Son, Coc Sau ... ), the
outermost is the ore with high Ag content (as Na Dieu ...), furthermore is hydrothermal
quartz veins containing gold.
The wallrocks were hydrothermally altered, popular is quartztization, and in fewer
grades are chloritization, sericitization, greisenization (in granite rock), dolomitization and
carbonatization.
The ore bodies within these deposits are veinform, stockwork, lens or lens chain
forms crossed the wallrock or they were formed by metacomatic process in carbonate
rock within combination of carbonate-terrigene rocks, caused complicate misshapen
form similar to the ore bodies within carbonate rocks in Cho Dien-Cho Don.
The major ore elements are Pb and Zn. Some ore bodies through fire assaying
analysis was found to contain gold. In addition to Pb and Zn, the deposits in Ngan Son
have relatively high grades of the elements Sn, Ag, Cd.
The primary ore mineral components are including sphalerite, galenite, pyrite and
arsenopyrite; secondary are chalcopyrite, pyrrhotite, cassiterite, stannin, grey copper,
magnetite, hematite, ilmenite and rutile and it also show the horizontal zonation: in the
contact zone of granite intrusion the mineral component are mainly arsenopyrite,
pyrite and cassiterite; in the deposits of middle zone, the ore mineral components are
mainly pyrite, sphalerite, galena and chalcopyrite (Coc Sau). In the deposits
distributed far from intrusion, the content of galena increased whiles the content of
arsenopyrite, pyrite clearly decreased. Polymetallic ores in Ngan Son were formed in
several stages:
1. Quartz-cassiterite-sulfide (arsenopyrite, pyrite) stage.
2. Sphalerite-stannine stage.
3. Galena-calcite with sulpho-salt Ag stage
18
All the signs such as material composition, form of ore bodies, geological
features ... reflect that the Ngan Son polymetallic ore is hydrothermal genetic type.
The regional zonation of mineral deposits (including lead-zinc deposits) around the
Ngan Son granite intrusion show that lead-zinc mineralization here genetically related
to this magmatic intrusion.
3.4. The veinform lead-zinc ore formation in terrigene and terrigene
alternated with effusive rock formation
The number of deposits and ore occurrences of this type is scattered in many places, in the
terrigene alternated with carbonate sedimentary formation; terrigene and terrigene alternated
effusive formation of Mesozoic age.... Some deposits, ore occurrences had been investigated and
estimated such as the Khuon Vac, Cuc Duong, Na Chanh, Khuon Ang deposits.
Ore is located along the shear and crushed zone, accompagned with the faults or
delamination in the presence of sedimentary rocks. The ore bodie are veinform,
lenseform crossed the wallrock. The ore bodies are generally small in size, grades of
Pb, Zn are poor.
The ore composition is often simple, including galena, sphalerite, pyrite and less
chalcopyrite, arsenopyrite and pyrrhotite. The wallrock alteration is usually quartzitization,
pyritization, chloritization and sericitization. The gangue minerals are mainly quartz.
Ore was formed mainly by mode of filling cracks, faults and shear zones. These
ore occurrences are clearly hydrothermal genetic.
3.5. Origin of lead-zince ore mines in Viet Bac zone
Based on available documents and own studies, I assumed that the lead-zince ore
mines in Viet Bac zone belong to two types of genesis:
- The deposits at Cho Dien – Cho Don and Tong Ba – Bac Me areas, with
alternation of different ore bodies (stratiform, crossed veins) in terrigenic carbonate,
terrigenic carbaonate alternated with effusive rocks of Pia Phuong and Tong Ba
formation, are assumed to be polygenetic and polyperiodic type, in which, the
stratiform ore bodies in primary orgin are paragenesis with the hosted rocks.
- Tin-bearing polymetallic deposits and the deposits with veinform orebodies in
sediments of different ages and compositions are belong to hydrothermal genesic
deposit group, related to granitoid magmatic activities.
Chapter 4
THE ROLES OF GEOLOGICAL FORMATIONS IN ORE FORMING PROCESS
AND TYPES OF LEAD-ZINC METALLOGENIC FORMATION
IN VIET BAC AREA
4.1. The roles of geological formations in ore forming process in Viet Bac area
4.1.1. The roles of carbonate-terrigene sedimentary alternating with volcanic and
subvolcanic rock formations in lead-zinc ore forming process.
These formations are distributed in a range, extended by the northwestsoutheast direction from Tong Ba to Bac Me, including two-mica quartz schist,
Calcareous micaceous quartz shist, orthophyr and syenite.
In the presence of hydrothermal epigenetic veinform ore bodies and the
syngenetic hydrothermal-sedimentary ore bodies, the carbonate rock (alternating
terrigene rocks) serves both ore-hosted (TVQ) and ore-bearing (TMQ) roles.
The ICP analysis results of samples in two areas Na Son and Suoi Thau-Ban Kep show
that in syenite, orthophyr, average grades of the elements Pb, Zn, Cu (Ag, Cd) is relatively high
19
compared with Clark values. This permit to predict that Tong Ba subvolcanic granitoid
complex can be a source supplying Pb, Zn and other ore associated elements. Apart that, the
closeness in space with the ore body allows predicting that this magmatic formation was also a
source of energy for the ore-forming process.
Thus, it can be considered that above subvolcanic intrusions play ore-genetic
role (TSQ) and also act as ore-forming role (TTQ).
4.1.2. The roles of carbonate sedimentary formations in lead-zinc ore forming process.
The role of above sedimentary formation on the lead-zinc ore-forming process
can be assessed as follows:
- The carbonate sedimentary rocks of D1 age of Tong Ba, Pia Phuong formations play
ore-bearing role (TMQ) for the syngenetic stratiform ore bodies also play ore-hosted
role for epigenetic veins form ore bodies.
- The carbonate sedimentary rocks of Mia Le formation (D1 age) mainly play orehosted role, with varied presence of hydrothermal vein form ore bodies.
- The others carbonate sedimentary rocks (Chang Pung, Bac Son formations) only
serve as ore-hosted role, but this role was very limited.
4.1.3. The roles of terrigene and terrigene alternated with effusive formations of
Mesozoic age in lead-zinc ore forming process
The terrigene and terrigene alternated with effusive formations of Mesozoic age
containing lead-zinc ore are including subcontinental sedimental formations of Lang
Son (T1ls), Na Khuat (T2nk), Mau Son (T3ms) formation and terigene sediments
interbedded with effusive rhyolite of Song Hien formation (T1sh).
The ore bodies in these formations are veinform, lenseform ore bodies, infilled
shear, tectonic cataclasic zones, positioned and closely controlled by these epigenetic
tectural-structural factors. Epigenetic nature of mineralization of ore bodies confirmed
ore-hosted role (TVQ) of these formations.
4.1.4. The roles of magmatic intrusive formation in lead-zinc ore forming process
In most cases, it is difficult to determine the hydrothermal lead-zinc deposits geneticly
related to a specific magmatic intrusion. The analysis of the relationship of space and data on
geochemical characteristics, isotopic analysis... allows temporary identify magmatic
intrusions are capable geneticly relate to lead-zinc mineralization as follows:
1. Phia Ma alkalic granitoid complex (PZ2pm): include Phia Ma syenite and
Tang Khoang granite-syenite intrusions, among that lead-zinc mineralization
distributed closely Tang Khoang intrusion. In secondary mineral components often
encountered magnetite, galena and sphalerite. The grades of some elements were
increased such as Cu, Sn, Pb, Ag, Sn, and La.
2. Mid Paleozoic granite-granodiorite complex (γaD3ns): Many research works on
granitoid and Pb-Zn mineralization in Ngan Son region show that between Ngan Son
granitoid intrusion and Pb-Zn minerralization has a certain relationship. It is ore zonation
around the granitoid intrusion: The horizontal zonation is clearly shown from the center of
the anticline and from granitoid intrusion to outer: W Sn Fe Pb, Zn Au Sb.
4.1.5. The roles of tectonic structural factos in lead-zinc forming process
4.1.5.1. Regional tectonic factors: it is the arc fault systems.
4.1.5.2. Local tectonic factors: The faults of different directions, depending on
region and brachyanticlines.
4.1.5.3. Detailled tectonic structural factors: Cleavages, faults, fractures, shear zones.
20
4.2. The types of lead-zinc metallogenic formation of Viet Bac area.
4.2.1. The metallogenic formation of TMQ=TVQ type: are carbonate-terrigene
sediments of D1 age belonging Pia Phuong formation. It can be considered as a
geological formation with mixture of carbonate and terrigene compenents (carbonate
sediments dominated) and it play both ore-bearing role (stratiform ore bdies) and
veinform ore bodies hosted role (TMQ=TVQ).
This type of metallogenic formation closely associated with lead-zinc ore
formation in carbonate sedimentary formation, among that typical is ore type of
galena-sphalerite-pyrite in carbonate rock (Cho Dien type).
In Pia Phuong formation distributed a serie of largest lead-zinc deposit in Viet
Nam in Cho Dien-Cho Don, Tuyen Quang… with variety of lead-zinc ore body types.
4.2.2. The metallogenic formation of (TVQ=TMQ) + (TTQ=TSQ) type: in this
type of metallogenic formation, there is formation of mixtured components including
carbonate-terrigene sediment alternated with effusive rock of Tong Ba formation
(D1tb) and effusive formation of acid alkalic component (rhyotrachyte) and
subvolcanic formation of orthophyr and syenite components, among that carbonateterrigne mixtured formations played ore-bearing role with syngenetic stratiform ore
bodies within it and ore-hosted role (with epigenetic veinform ore bodie crossed above
rocks). Volcanic, subvolcanic formations may be one of the supplied material sources
for forming process of hydrothermal ore bodies, it’s also provide energy for the ore
forming process, so it played both ore-genetic (TSQ) role and ore-forming (TTQ) role.
This type of metallogenic formation related to lead-zinc ore formation in
carbonate-terrigene sedimentary formation alternated with volcanic and subvolcanic
rocks, among that there is ore type of sphalerite-pyrite-galena-chalcopyrite (Na Son
type) and galena-sphalerite bearing silver (Ban Lin type).
4.2.3. Metallogenic formation of TVQ+TSQ type
In Viet Bac area, the main formations played only a ore-hosted role (bearing leadzinc ore) are defined as the formations belonging Mia Le (D1ml), Lang Son (T1ls), Song
Hien (T1sh), Na Khuat (T2nk), Mau Son (T3ms) formations. Regarding the formations
played ore-genetic role, except Ngan Son granitoid intrusion, most of them have not been
identified in other areas. These types of formations in VietBac area include:
+ The lead-zinc metallogenic formation of TVQ+TSQ type, which identify both the
TVQ and the TSQ: It is comination of Ngan Son magmatic complex (played ore-genetic
role - TSQ) and surrounded it carbonate-terrigene sediments of Mia Le formation (played
ore-hosted role - TVQ). This type of formation related to Pb-Zn deposits and thin bearing
polymetallic sulfide deposits surrounded this granite intrusion.
+ The lead-zinc metallogenic formations of TVQ+TSQ type, which identified
only the TVQ: Carbonate-terrigene sedimentary formations of Paleozoic age (Mia Le
formation), terrigene sedimentary rocks, terrigene sedimentary rock alternated with
effusive rocks of Mesozoic age of Lang Son (T1ls), Song Hien (T1sh), Na
Khuat (T2nk) và Mau Son (T3ms) formations. These formations played hydrothermal
ore body hosted role; the formation that played ore-genetic role (material supplied
source) had not been defined, is supposed to be magmatic intrusions in the deep.
21
Chapter 5
DISTRIBUTION REGULARITIES OF TYPES OF LEAD-ZINC
METALLOGENIC FORMATION IN VIET BAC AREA.
As disscused above, the types of lead-zinc metallogenic formation in Viet Bac
area included 3 types: 1) Metallogenic formation of TVQ=TMQ type; 2) Metallogenic
formation of (TVQ=TMQ)+(TTQ=TSQ) type; 3) Metallogenic formation of
TVQ=TMQ type; 2) Metallogenic formation of TVQ+TSQ type.
5.1. Distribution regularities of types of lead-zinc metallogenic in space.
5.1.1. Distribution regularities of metallogenic formation of TVQ=TMQ type
This metallogenic formation included carbonate-terrigene sediments of Pia
Phuong formation, lead-zinc mineralization features of which are syngenetic stratiform
ore bodies, therefore geological setting to form this metallogenic formation was also
geological setting to form above sedimentary formation. Accordingly that, the Pia
Phuong formation closely associated with the lithotectonic assemblage of DevonianPermian passive continental margin, characterized by the terrigene, siliceous terrigene
and carbonate rocks of Early Devonian formation (Tran Van Tri et al., 2009).
Regarding the space, Pia Phuong formation mainly distributed on Lo Gam uplift
structural zone, surrounded on the east and southeast of the Song Chay dome. The
composition of the formation consists of calcareous shist, sericite shist, limestone,
dolomite limestone, bituminous limestone, shist, marble, shist alternated with
sandstone and siltstone, calcareous sandstone, sandstone and siltstone interbedded by
calcareous phylit, calcareous-siliceous claystone, quartzitic sandstone, siliceous
limestone, tuffeous sandstone, rhyolite tuff.
5.1.2. Distribution regularities of metallogenic formation of (TVQ=TMQ) +
(TTQ=TSQ) type
This metallogenic formation included the mixtured carbonate-terrigene rock
with acid alkalic volcanic and subvolcanic rock of Tong Ba formation (D1tb).
According to the tectonic documents (Duong Duc Kiem, 2005; Tran Van Tri,
2009), the forming of this formation was also closely associated with lithotectonic
assemblage of Devonian-Permian continental passive margin, in which metallogenic
formation is in Tong Ba intracontinental rift structure, belonging volcanic-plutonic
assemblage included trachyporphyr, rhyolite interbedded in Devonian sediment in Tong
Ba-Bac Me range, syenite porphyr, granosyenite subvolcanic intrusions crossed up host
rock, caused metamorphism at grade of green shist to epidote-amphibolite facies.
In terms of space, Tong Ba formation had the distribution at the North of study
area, fully in Phu Ngu-Tong Ba structural zone, created a range, extended in the
northwest-southeast from Tong Ba to Bac Me. This formation has specific feature that
upper part containt thick layer of effusive rock alternating with seams of iron ore.
In this formation, presented a serie of lead-zinc deposits: Na Son, Ta Pan, Suoi
Thau, Ban Bo, Phieng Phat, Yen Tho, Ban Lin, Phia Dam… with industrial valuable
stratiform and veinform ore bodies.
5.1.3. Distribution regularities of metallogenic formation of TVQ+TSQ type
With the large age range of ore-hosted formations, clearly this type of metallogenic
formation belonged different lithotectonic assemblages or in other words, in the study
area there are many different metallogenic formations of TVQ+TSQ types.
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In general, these formations is mainly distributed in Bac Thai - Bac Son
anticlinorium, coinciding with tectonic units Bac Bo Northeastern Early Paleozoic
orogenic belt (Tran Van Tri, 2009), some part (the rock of Le Mia formation)
distributed in the eastern part of the structural block. They formed the Pia Oac, Ngan
Son, Coc Keng-Sy Binh, Lang Hit, Dong Mo and Tam Dao ore knots with a variety of
lead-zinc deposits of small scale.
5.2. Distribution regularities of lead-zinc metallogenic formations in time.
Lead-zinc ore in study area was formed in 3 metallogenic epochs, is Preindosini,
Indosini and Yanshan.
- Preindosinian metallogenic epoch: that Pb-Zn mineralization belonging Early
Paleozoic ore forming period with formation of deposits, containing syngenetic
stratiform ore bodies, closely in time associated with sediments of D1 age in Tong BaBac Me and Cho Dien-Cho Don areas.
- Indosinian metallogenic epoch: Matched to this epoch is formation of lead-zinc
veinform deposits in the area. Mineralization was happened in period of Late
Paleozoic-Early Mesozoic tectonic activity, about from Permi to Triass (P-T), in a
period having a multi-stage developped overlap mineralization, it is also the time of
the orogenic, magmatic and metamorphic activity occurred most strongly.
- Yanshanian metallogenic epoch: In this epoch, are formed lead-zinc veinform in
terrigene sediment and terrigene sediment alternated with effusive rock of Mesozoic
age and capable of some veinform ore bodies in the sediment of Paleozoic age.
5.3. Prognostic metallogenic zonation
On the basis of established lead-zinc metallogenic formations, in terms of their
distribution and mutual position with the tectonic structural elements can be identified
in the study area has three lead-zinc metallogenic zones with the ore knots (the ore
regions) and ore fields as follows:
- Tong Ba-Bac Me lead-zinc metallogenic zone: mainly associated with
metallogenic formation of (TVQ=TMQ) + (TTQ=TSQ) type with galena-sphaleritechalcopyrite (bearing silver), includes Na Son and Ban Lim ore knots.
- Led-zinc metallogenic zone of East Song Lo dome: mainly associated with
metallogenic formation of TVQ=TMQ type with typical ore formation is galenasphalerite-pyrite (Cho Dien type), includes ore knots and ore region: Cho Dien-Cho
Don ore geion includes 2 ore fields Cho Dien and Cho Don; Tuyen Quang ore knot;
Son Duong ore knot.
- Bac Thai-Bac Son lead-zinc metallogenic zone: mainly associated with metallogenic
formation of TVQ=TMQ type, featured by variety of lead-zinc mineralization types,
includes 6 ore knots: Oia Oac; Ngan Son; Coc Keng-Sy Binh (including 2 ore fields: Sy
Binh and Coc Keng); Lang Hit (including 2 ore fields: Lang Hit and La Hien-Cuc Duong);
Dong Mo and Tam Dao ore knot.
5.4.1 Mineralization premise and ore guide for prospection
5.4.1. The premise for prospection
+ Petostragrapic premise:
- For metallogenic formation of TVQ=TMQ type: The layers of limestone,
marble limestone, dolomitizated limestone of the Pia Phương (D1pp) and Mia Lé
(D1ml) formations are importante premises to prospect for ore bodies within it.
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- For metallogenic formation of (TVQ=TMQ)+(TTQ=TSQ) type: the carbonate
rock of Tong Ba formation (D1tb) are premise to prospect for straiform lead-zinc ore
bodies; terrigene rock and acid alkalic volcanic and subvolcanic rocks within it
belonging above formation are premise to prospect for veinform ore bodies;
- For metallogenic formation of TVQ+TSQ type: The layers of carbonate rock
alternated terrigene sediment of Mia Le formation (D1ml) are relatively importante
premise for hydrothermal lead-zinc mineralization; terigene sedimentary rock, terigene
sedimentary alternated with effusive rocks containing carbonate component of Lang
Son (T1ls), Song Hien (T1sh), Na Khuat (T2nk) và Mau Son (T3ms) formations ppay
limited role of lead-zinc mineralization.
+ Magmatic premise: with a ore-genetic role, the magma is considered to be the
premise for prospecting lead-zinc ore in the study area is alkaline granitoid intrusiion of
Phia Ma complex ((PZ2pm) and granitic intrusive complex Ngan Son (γD3ns)
+ Tectonic structural premise: It is the brachyanticlines and the local faults,
fractures role of that for lead-zinc ore forming in study aea has been confirmed.
5.4.2. Ore guide for prospection
- Ore outcrops;
- Halo of ore dispersion;
- Hydrothermal alterations: calcitization, dolomitization are effective ore guide
to prospect lead-zinc ore bodie in carbonate rock; chloritization, quartzitization are
popular in ore-hosted allumosiliceous rocks.
- Geochemical secondary dispersion halo of Pb and Zn elements.
CONCLUSIONS AND RECOMENDATIONS
Conclusions
1. On the basis of environmental ore-hosted rock, ore body morphological
characteristics and ore material composition, lead-zinc deposits in the Viet Bac area
were classified into four types of ore formation:
- The lead-zinc ore formation in the carbonate-terrigene sediments alternated with
volcanic and subvolcanic rocks with two ore types: galena-sphalerite-chalcopyrite and
bearing silver galena-sphalerite.
- The lead-zinc ore formation in the carbonate sedimentary formation with 3 ore
types: galena-sphalerite-pyrite of Cho Dien type, galena-sphalerite of Lang Hit type
and galena-sphalerite-barite of Luc Ba type.
- The tin bearing veinform lead-zinc ore formation in carbonate-terrigene
sedimentary formation.
- The vein form lead-zinc ore formation in the terrigene and terrigene alternated
with volcanic rock sedimentary formations of MZ age.
2. In the Viet Bac area there’s three lead-zinc metallogenic formations, including:
- Metallogenic formation of TVQ=TMQ type featured by lead-zinc ore formation in the
carbonate sedimentary formations (deposits in Cho Dien-Cho Don, Tuyen Quang…).
- Metallogenic formation of (TVQ=TMQ) + (TTQ=TSQ) type featured by leadzinc ore formation in the carbonate-terrigene alternated with acid alkalic volcanic and
subvolcanic rocks sedimentary formations (deposits in Tong Ba-Bac Me).
- Metallogenic formation of (TVQ=TMQ)+(TTQ=TSQ) type featured by the
veinform lead-zinc ore formation in the terrigene-carbonate sedimentary formation
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(deposits in Ngan Son) and the veinform lead-zinc ore formation in the terrigene and
terrigene alternated with volcanic rock sedimentary formations of MZ age.
3. Each type of metallogenic formation in the Viet Bac area closely related in
space and time with the specific lithotectonic assemblage:
- Metallogenic formation of TVQ=TMQ and (TVQ=TMQ) + (TTQ=TSQ) types
related to lithotectonic assemblage of Devonian-Permian passive continental margin.
- Metallogenic formations of TVQ+TSQ type related to different lithotectonic
assemblages, mainly Northeastern zone of Bac Bo: lithotectonic assemblage of
Devonian-Permian passive continental margin; lithotectonic assemblage of Late
Permian-Triassic sedimentary and volcanic-plutonic intracontinental rift; assemblage
of Mid-Late Triassic continental, subcontinental molasses.
4. In Viet Bac area, lead-zinc mineralization was formed in 3 major metallogenic
epochs as following:
- Preindosinien metallogenic epoch related to metallogenic formations of
TVQ=TMQ and (TVQ=TMQ)+(TTQ=TSQ) types.
- Indosinien metallogenic epoch related to metallogenic formation of TVQ+TSQ type.
- Yanshanian metallogenic epoch related to metallogenic formation of TVQ+TSQ type.
5. Lead-zinc mineralization distribute in 3 lead-zinc metallogenic zones: Tong Ba-Bac
Me lead-zinc metallogenic zone; lead-zinc metallogenic zone of East Song Lo dome; Bac
Thai-Bac Son lead-zinc metallogenic zone, with 11 ore regions and ore knots, mathed with
3 tectonic-structural zone: Phu Ngu-Tong Ba zone; Song Lo anticlinirium and Bac ThaiBac Son anticlinirium.
Recomendations
1. For the researching work:
- More research is needed on the relationship between magmatism with lead-zinc
mineralization in study area.
- More detail research on typical deposits, where there is lead-zinc stratiform and veinform
ore bodies; nature of stratiform beside veinform ore bodies, thereby modeling the deposits.
2. For the prospecting and exploration works:
- Tong Ba-Bac Me region: to carry out expansible prospection and reserves
upgrading exploration for evaluated deposits.
- Cho Don-Cho Dien region: To carry out the reserves upgrading exploration for
the evaluated deposits, to carry out expandible exploration for the explored mine and
continue to prospect for hidden mineralization in the depth.
- Tuyen Quang-The Son Duong region: focus on detailed prospection around the
Dao Vien anticline, area between the Lo and Gam Rivers and area along the Lo River
from the Tuyen Quang town to Son Duong to the east.
- Lang Hit region: to carry out expansible prospection; exploration for ore
deposits in the north to increase ore reserves in conditions favorable infrastructure.
Thesis "Study on characteristics and distribution regularities of lead-zinc
metallogenic formations in the Viet Bac area” have solved the set objectives, firstly
established the metallogenic formations of lead-zinc mineralization in view of applied
metallogeny and clarify their distribution rules, have also identified ore controling
factors and the premise of lead-zinc mineralization, ore guide for prospection and
estimation of lead-zinc ore prospects in the study area.
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LIST OF PUBLISHED WORKS OF AUTHORS
1. Hoang Van Khoa, Nguyen Viet Hung, Dao Thai Bac (2000). "Some of the
assessment results in the area lead-zinc ore DB 10 years (1990-2000)",
Summary of reports in sciencific Conference of Gelogy and Minerals in
2000, Department of Geology and Minerals of Vietnam, P. 36.
2. Dao Thai Bac, Phan Van San, Tran Van Mien (2002), "Analysis of physical
tectonic characteristics related to the lead-zinc ore formation of Thuong
Am-Son Duong-Tuyen Quang area", The Collection Report of 15th
Sciencific Conference, Tome 2- Geology and Minerals, Hanoi University of
Mining and Geology, P.12-15.
3. Nguyen Quang Luat, Dao Thai Bac, Phan Van San, (2004), "Characteristics
of mineral composition, lead-zinc ore structure & texture of Thuong Am
area", Collection reports of 16th scientific conference, Tome 2 - Geology
and Minerals, Hanoi University of Mining and Geology, P.108-114.
4. Tran My Dung, Liu Junlai, Nguyen Quang Luat, Dao Thai Bac (2009), "ReOs dating of molybdenite from the Ô Quy Hồ - Bản Khoang molybdenum
mineralization belt and its geological significance ", Journal of Geology,
series A, No. 313 7-8/2009, Department of Geology and Minerals of
Vietnam, (80), P.56-65.
5. Dao Thai Bac (2009), "Characteristics of lead-zinc ores in the Mesozoic
sedimentary-effusive formations in Bac Bo region", Journal of Geology,
series A, No. 320 9-10/2009, Department of Geology and Minerals of
Vietnam, (528), P.375-381.
6. Dao Thai Bac, Tran My Dung (2010), "The source type of ore forming
solution in some lead-zinc deposits of Viet Bac area in the sedimentary
carbonate-terrigene and carbonate-terrigene alternated with effusive rocks of
D1 age through the isotopic analysis results of lead and sulfur”, Collection
reports of 19th scientific conference, Tome 3 - Geology and Minerals, Hanoi
University of Mining and Geology, (275), tr.187-193.
7. Dao Thai Bac, Nguyen Quang Luat (2011), “Metallogenic formation types of
lead-zinc mineralization in Việt Bắc zone”, Journal of Geology, series A, No.
323 1-2/2011, Department of Geology and Minerals of Vietnam, (94), P. 3646.