Download Intrusive Igneous Activity

by: Mary Therese Maurin
▫ body of intrusive
igneous rock that is
crystallized from
magma slowly cooling
below the surface of the
Earth.
▫ Named after the greek
god “Pluto”.
Dikes-tabular discordant bodies that are produced when
magma is injected into the fractures.
Sills-tabular plutons formed when magma is injected
along sedimentary bedding surfaces.
Batholiths-largest intrusive igneous bodies that
composed the core of mountain systems.
Laccoliths-magma generated by it is viscous
.This less fluid magma collects as a lens-shaped
mass that arches the overlying strata upwards.
Generating
from Solid Rocks
Magma originates when essentially solid rock,located in
the crust and the upper mantle,melts.
Role of
 Geothermal Gradientchange in temperature as
depth changes: at a depth
of 100 km has a
temperature that ranges
between 1200-1400
degrees Celsius.
 Through raising the
temperature above the level
makes the rock melt.
Anywhere there is a rising convection current, hotter
material at depth will
carrying its heat with it.to be
replaced by descending cooler material in a convection
cell.
Role of
Pressure is release
thereby lowering it
Mantle convection helps in raising the geothermal
gradient as a result confining pressure is reduced thus
triggering decompression melting. Pressure
(decrease of pressure favors melt, less dense packing
is allowed)
Role of
As a plate descends, the pressures and temperatures it experiences increase, and
the water-laden sediments are baked (metamorphosed) and squeezed into new types
of rock. The released water immediately vaporizes at these temperatures and pressures,
and the vapor rises. As the vapor moves upward, it enters hotter rocks.The presence
of the water in its vapor phase causes the melting point to decrease and the rock to
melt and absorb the vapor.
As an oceanic plate sinks,both heat and pressure drive water
from the subducting crystal rocks.These volatiles which are very
mobile migrate into the wedge of the mantle lowering the melting
temperature to sufficiently generate magma.
and
Compositions
• Igneous Rocks
• Melt over a
temperature range
of about 200
degrees Celsius.
• Undergoes the
process called
Partial Melting to
generate Magma
As the slab sinks deeper(100-150km) into the mantle,increase
in temperature and pressure drives volatiles from the oceanic
crust.These fluids reduce the melting point triggering hot
mantle rock to melt consequently the accumulated magma
slowly rises.
IGNEOUS ACTIVITY AT CONVERGENT
PLATE BOUNDARIES
IGNEOUS ACTIVITY AT CONVERGENT
PLATE BOUNDARIES
• As the plates are being pulled apart,solid yet
mobile mantle responds to the decrease in
overburden and rises upward to fill in the rift.
• Rock rises=decrease in pressure=undergoes
melting without the addition of
heat(decompression melting)
IGNEOUS ACTIVITY AT DIVERGENT
PLATE BOUNDARIES
IGNEOUS ACTIVITY AT DIVERGENT
PLATE BOUNDARIES
INTRAPLATE IGNEOUS ACTIVITY
1.
2.
3.
4.
Changes in the pattern of volcanic earthquakes
Expansion of a near-surface magma chamber leading to the inflation
of a volcano
Changes in the amount and/or composition of the gases that are
released
An increase in ground temperature caused by the emplacement of
new magma