Download Kochemasov

ZEOLITES AS A POSSIBLE SINK FOR IMPORTANT AMOUNTS OF CONSTITUENT WATER IN THE
MARTIAN CRUST. G.G. Kochemasov, IGEM of the Russian Academy of Sciences, 35 Staromonetny, 119017
Moscow, Russia, [email protected]
Now, when martian water in form of ice and aqueous salts is firmly established, we draw attention to another
important source of constituent water, namely, zeolites [1]. It is a suitable time to speak about it because direct
observations (Spirit) indicate that lightly colored mountain massifs near the highland-lowland dichotomy boundary
probably presenting outliers of light (in sense of color and density) southern continental segment, are composed of
layered sequences of highly alkaline rocks. This kind of lithology for for martian highlands was predicted earlier
before “Pathfinder” landing on basis of the wave planetology [2]. The latter requires that in rotating celestial bodies
(but all celestial bodies rotate) the higher hypsometric and tectonic differences between tectonic blocks the higher
density difference between composing them lithologies (the requirement of leveling blocks’ angular momenta).
Thus, comparing 3 terrestrial group planets: Venus, Earth, Mars, we have shown that their tectonic granulations
become coarser (and, hence, hypsometric difference between “granules’ higher) with increasing distance from Sun
[2]. This granulation has sizes inversely proportional to the planets’ orbital frequencies: Venus πR/6, Earth πR/4,
Mars πR/2 (R-planets’ radius). For ‘fine” granulated Venus necessary density difference (contrast) between ”ups”(+)
and “downs” (-) is satisfied by such opposing lithologies as denser Mg-basalts (-) and less dense alkaline basalts (+).
For “middle” granulated Earth a sharper density difference between tholeiites (-) and andesites (an average continent
composition) (+) is satisfactory. All mentioned lithologies are observed instrumentally in situ. For “coarse”
granulated Mars at that time (1995) we had only measured Fe-basalts of the northern lowlands (-) (“Vikings”) To
balance them we predicted for highly standing highlands such light lithologies as syenites, albitites, granites [2].
“Pathfinder’ has found andesites (rocks enriched with Si, Al, K) at the highland-lowland contact. We insisted on
more acid and lighter rocks further south from the contact (to balance high hypsometric and tectonic difference
between “+” and “-“). “Odyssey” has identified dacites [3]. But direct ‘Spirit”’s observations of light-colored rocks
at Columbia Hills show that they really are Al, Na, K-rich, often Fe-poor and, thus, represent rocks of alkaline
affinity. Nepheline-normative rocks were already observed in the first analyses of the Gusev crater basalts [4]. These
basalts are also Mg-rich: increase of Mg/Fe in basalts in the southern direction indicates that they loose their density
from blocks “-“ to blocks “+” (compare the same tendency at Earth: Mg/Fe is lower in the ocean-floor basalts and
higher in the continental ones).
Columbia Hills rocks are thinly layered and sharply change their composition in rather small vertical section
(about 100 m) as it is typical for the terrestrial nepheline syenites. The best suitable example of them is the Lovozero
massif of layered nepheline syenites at Kola Peninsula [5]. This massif (650 square km) consists of thin and variable
thickness layers of lujavrites, foyaites, urtites containing nepheline, sodalite, other feldspathoids and minerals of Zr,
Ti, Nb, Ta, TR, P, S, F. Pegmatites are often with natrolite. A very typical process of hydrothermal and surface
alteration of feldspathoids is their zeolitization (development of natrolite and other zeolites, shpreusteinization –
mixture of zeolites). Sodalite typically is converted to hydrosodalite. In other words, nepheline syenites are highly
hydrated. At Mars this constituent water tied to zeolites and hydrosodalite can be converted to free water and again
hidden into crystalline lattice under changing P-T conditions. Thus, huge amounts of hidden water can be
“suddenly” released to produce intermittent disappearing surface flows. Traces of such flows and seepages are easily
observed on numerous images. Some detailed images of brushed and scraped surfaces of Columbia Hills rocks have
structures and textures resembling those of nepheline syenites, in particular, directed textures, oriented laths,
poikilitic structures. Some fragments of rocks contain rounded and angular xenoliths also typical for terrestrial
syenites. Some fragments are rotten and easily abraded what is also typical for weathered feldspathoid rocks.
A large amount of volatiles in the martian highland crust indicates that Mars is slightly degassed. If degassing is
proportional to orbital frequencies (wiping out volatiles is higher in bodies with higher orb. fr.) then Venus is
thoroughly outgassed (all volatiles are in its atmosphere and lithosphere is dry), Earth –moderately (there is an
important atmosphere and volatile-rich crust), Mars –mildly (a lot of volatiles still in the crust). Volatiles (and water
in particular) facilitate chemical fractionation in the mantle and crust. This is necessary to produce highly alkaline,
water and salt rich highlands observed at Mars. Salts and other aqueous minerals have low density that diminishes
overall highland density required by the wave planetology. References: [1] Kochemasov G.G. (2002) 36th VernadskyBrown microsymposium “Topics in comparative planetology”, Abstr., Oct. 14-16 2002, Vernadsky Inst., Moscow, Russia, CDROM; [2] Kochemasov G.G. (1995) Golombek M.P., Edgett K.S., Rice J.W.Jr. (eds) Mars Pathfinder landing site workshop II:
Characteristics of the Ares Vallis region and Field trips to the Channeled Scabland, Washington. LPI Tech. Rpt. 95-01, Pt. 1, LPI,
Houston, 63 pp.; [3] Christensen P.R., McSween H.Y.Jr., Bandfield J.L. et al (2005) LPSC XXXVI, Abstr. # 1273, CD-ROM;
[4] Gellert R., Rieder R., Anderson R.C. et al. (2004) Science, v. 305, # 5685, 829-832; [5] Kochemasov G.G. (2005) VernadskyBrown Microsymp.-42, Moscow, Oct. 2005, Abstr. M42_32, CD-ROM.