metamorphic crust development process,
existing sedimentary rocks,
magmatic rocks and other specific geological
in Under physical and chemical conditions,
formed rocks with new mineral assemblage and
structure.
(Figure source @James St. John)
metamorphic rocks in the global distribution of
very extensive.
has been produced in time from ancient times to
.
(FIG source @ americansouthwest.net)
(FIG source @ wolv / sgeologyscience.com)
(Image source @James St. John) How does the morphology of span1 span1 strong_strong_strong_strong_strong_strong_strong_strong 5span?
What are the characteristics of ?
01
The metamorphic rock is the product of the existing rock
undergoing the metamorphism of .
Its rock characteristics (material composition,
structure, appearance, etc.) _p11sp span1p
are affected by the metamorphic characteristics.
tectonic backdrop when
(FIG source @letslearngeology)
to produce metamorphism,
Based on the physical and chemical process of metamorphism and the connection between
and other geological processes,
_span_spansppansppan1span_span11 can be divided into multiple types of common metamorphisms. as it follows: metamorphism
region refers
metamorphism factor complex and
by A metamorphic effect of
that affects a wide range of rocks.
(FIG source @ geologyin.com)
rock in a wide range,
temperature, pressure, fluid Under the influence of other factors,
undergoes recrystallization , metamorphic crystallization, deformation,
sometimes 1 1 _spanp 1 _spanp effect.
large rock metamorphism
region has experienced widespread ranging
degree of deterioration.
Usually the low metamorphic zone retains some minerals and structures of the original rock
high-grade metamorphic zone is often accompanied by
magmatic action and mixed lithification.
(FIG source @ geologyin.com)
contact metamorphism in magmatic
Under the influence of
surrounding rock is mainly affected by the temperature of the magma body
, which usually produces a large scale of local metamorphism.
contact metamorphism
cause thermal energy from the magma
contacting zone rock mineral composition occurs and
whose structure has changed but the chemical composition has not changed. The metamorphism is called thermal contact metamorphism.
can form angle rocks, spots slate , etc.
thermally contact metamorphic rocks.
rock angle (FIG source @ Max.kit)
account by the magma Surrounding it
chemical composition , Mineral composition and structure
all change metamorphism,
is called contact metamorphism, _spanspan5 spanspan_span5 spanspanspanspanspanspanspanspanspanspanspanspanspanspanspanspanspanspanspanspanspanspanspanspanspanspanspanspanspanspanspanspanspanspanspanspanspan
contact metamorphic rocks.
SKARN sections (FIG source @ Chmee2) under a microscope
heat (baked) metamorphism
A special thermal contact deterioration effect,
mainly refers to the
contact with extruded rocks or subvolcanic rocks or xenoliths.
Xenoliths (FIG source @ Wilson44691)
strong dynamic metamorphism
generated in the role configuration Under stress, the rocks of
are broken and deformed, and
is accompanied by a certain metamorphic crystallization and p1span
span qualitative metamorphism.Its development is often controlled by fault structures.
(FIG source @ slideshare.net)
hot gas and the solution was applied to
rock has been formed,
makes it produce mineral composition,
chemical composition and structural change of
1span gas change effect. hydrothermal metamorphism
(FIG source @Karla Panchuk)
metamorphism methods include
recrystallized Function, metamorphic crystallization,
metamorphic differentiation and metasomatism
strong2 and various deformation and fragmentation effects.
The mineral components in the rock are recrystallized in the solid state.
before and after recrystallization, the crystal form of the mineral,
size arrangement method
span1 span1 changes, but the composition does not change. The general trend ofis that the crystal grains increase, and
becomes a mineral with a smaller molecular volume. metamorphic crystallization recrystallization
refers
pressure at a temperature in the range of metamorphism,
Under the condition that the original rock remains basically solid,
is the formation process of new mineral facies,
1span _p and the corresponding minerals must disappear at the same time. .
metamorphic crystallization
metamorphic differentiation means
uniform composition original rock,
After undergoes metamorphism,
has uneven mineral composition
.
mineral components unevenness
the metamorphism,
change in the chemical composition of the original rock is
a kind of complex material replacement,
is called metasomatism.
This is a widely distributed,
and very important diagenesis and mineralization.
(FIG source @ slideplayer.com)
02
The chemical composition of metamorphic rocks is complex and diverse.
It firstly depends on the chemical composition of the original rock,
is also related to the change of 1 and the activity of some elements in the process of metamorphism 1 and _p11sp p0 related.
(FIG source @Geology IN)
studies show that the original rock contained
H2O and CO2, etc. Volatile components,
progress with metamorphism,
will have significant changes in composition and content.
(FIG source @ Sashkin / Shutterstock)
Generally,
rocks containing low volatile high.
gradually decreases with the increase in temperature,
For example, in granulite and other high-temperature metamorphic rocks,
(OH) content is usually very low.
Granulite (FIG source @ sciencesource.com) of certain trace elements in the original rock
,
with temperature Increased, affected by metamorphic hydrothermal fluid,
often changes significantly.
such as Cu, Pb, Zn, Ca and so on
content
rock
major rock element oxide
general metamorphism
has no obvious change,
such as SiO2 , Al2O3, Fe2O3 and so on.
can therefore be used as one of the important criteria for judging the original rock type.
metamorphic rocks from the crust
magmatic rocks and sedimentary rocks existing ,
therefore not Few minerals are shared by the three major rock types,
but the mineral composition of metamorphic rocks is more complex than
magmatic rocks and sedimentary rocks.
feldspar (FIG source @World Atlas)
feldspar , quartz and mica
in Among magmatic rocks and metamorphic rocks,
are the main rock-forming minerals.
When rocks mainly by the mineral composition,
need to bind their structural configuration,
occurrence features, content or the symbiotic law,
to distinguish.
mica (FIG source @Pascal Terjan)
normal Magmatite e.g.,
low content of quartz More than 50%,
and in metamorphic rocks,
Its content range varies greatly, and 1p _p11span 95% can sometimes be as high as span.
Quartz (Source@mclanahan.com)
0p in minerals
The minerals in metamorphic rocks are compared with magmatic rocks.
has many differences.
, such as aluminum silicate
(Al2SiO5) minerals, _p11span_span_span_span_span_span_span_span_
0
In the rock.
andalusite (FIG source @Ivar Leidus)
general common metamorphic rocks,
concept by chemical series,
can be summarized as aluminum-rich series, felsic series,
_5 strong span_strong_span5 iron span5 strong_span5 span_strong_span5 iron strong_span5 Quality (ultra-basic) series,
carbonate series five series.
aluminum-rich rock of the general principles
shale sedimentary rocks, shale and rock such as clay,
which The chemical composition is characterized by rich aluminum.
The main minerals of this type of metamorphic rock are
mica , chlorite, and quartz.
chlorite (FIG source @EISCO)
felsic series of original rock
containing an amount of All kinds of feldspar sandstones,
intermediate-acid volcanic rocks, etc.,
chemical composition is basically equivalent to span5span span _p11sp p0 acidic lava.
The main minerals of this metamorphic rock are
quartz, acid plagioclase, biotite 5s or _span1 chrysotile _span1 span _span11.
biotite (picture source @James St. John series) _p11sp0
_span_span11
includes basic magmatic rock,
basic composition of tuffaceous hard sandstone, etc.
Therefore, the common minerals of this metamorphic rock are
chlorite, epidote, _span _span pyroxene, etc.
Hornblende (dark color) (Source @Rob Lavinsky/ iRocks.com) 11 super-iron-based span1 _pspan1 43 The series of original rocks
are generally ultrabasic magmatic rocks,
and some of the sedimentary rocks with extremely rich magnesium of special origin.
The metamorphic minerals that appear may include
talc, serpentine, mafic amphibole, etc.
talc (FIG source @Rob Lavinsky / iRocks.com)
original series carbonate rocks
Various limestone and dolomite etc.
This type of rock is in the process of heating metamorphism,
Except most of the carbonate minerals _p1span_span_span_span_span_span_p1p1p1p1p1spansp The other part of calcium and magnesium is combined with other oxides of
to form various silicates and
aluminosilicates, such as wollastonite.
wollastonite (light) (FIG source @Leon Hupperichs)
03
Structural structure is an important feature of metamorphic rocks.
is often used as a metamorphic rock
is one of the important basis for classification and naming.
For example, rocks with plate-like structure are called slate;
Rocks with plate-like structure are called schist and so on.
slate (FIG source @SlateUSGOV)
metamorphic range,
separable by Cause
variable residual (residual) structure, metamorphic structure,
metasomatic structure and fragmentation structure 1 span.
The surplus (residual) structure is still in the original metamorphic rock of _span5 span0 _span5 span0
is deterioration due to recrystallization is not complete,
structure wherein part of the original rock is preserved,
The variable I gravel-like structure,
becomes Remaining sand-like structure and so on.
variable surplus (residual) structure micrograph (source@literature[2]) _span_span1 _span1 _span1 _span1
crystals recrystallized in the solid state crystalline structure formed in rocks, is one of the typical structures of metamorphic rock, is like porphyritic metamorphic structure.
blastic structure micrograph (FIG @ Source Document [2])
account structure or metamorphism
During the process of mixed petrification,
is a structure formed by metasomatism.
can be divided into
according to different morphologies. Metasomatic illusion structure, metasomatic residual structure, 0 span
cross-striped structure, etc.
alternative structure (source@literature[3])
mineral grains in the rock is broken into
irregular shape angular debris,
debris often has a serrated edge,
and Frequent cracks, distortion and
wavy extinction and other phenomena.
fragmentation structure (FIG @ Source Document [2])
means configured metamorphic rock
each The spatial distribution characteristics of three minerals and the arrangement status of
can be divided into the following two categories according to their genesis.
The variable structure refers to the original features of metamorphic rock sp
span0 span0 _span5 span0.as metamorphic sedimentary rocks formed,
common variant I gravel-like structure,
variant I sand-like structure,
silt variant I状结构 etc.
I variant configuration (FIG source @ baidu.com)
means configured into
re-crystallization and metamorphic During the crystallization process, the structure formed by
,
occupies an important position in metamorphic rocks.
phyllitic structure (Figure source @SlideShare)
become common structure including
tumor-like structure , Slab structure,
thousand phyllostructure, sheet structure and
gneissic structure, etc.
gneissic structure (FIG source @ document [4])
The mineral composition,
content and structure, Structure,
Common main metamorphic rocks can be divided into
slate type, phyllite schist 5 type, _span1 type schist schist 5 type, _span1 type schist schist 5 type, _span1 type schist schist, _span1
slate lithology is a denser,
typically have a dense
rock plate-like cleavage .
slate (FIG source @Jonathan Zander)
phyllite a
fine grain microstructure Metamorphic rock,
The typical main mineral combination is
sericite-chlorite-quartz.
phyllite (FIG source @EdwardEMeyer)
schists mainly
lenticular sheet minerals (mica, Chlorite,
talc , serpentine, etc.) and
span1 Quartz and other granular minerals span1 Quartz.
schists (FIG source @Michael C. Rygel)
gneiss class consists mainly of quartz,
Feldspar and a small amount of dark mineral
(mica, hornblende, pyroxene)
.
gneiss (FIG source @flexiblelearning)
References:
[1] Wang Renmin. Metamorphic Petrology [M]. Geological Publishing House, _span1 span1 span5 Songspan, _span1 _span5 S, Cao Y. Textures and Structures of Metamorphic Rocks[J]. Encyclopedia of Geology (Second Edition), 2021:375-388.
[3] _span, Arai Span Yang Kób , et al. Silica enrichment of Group II xenoliths by evolved alkali basalt from Jeju Island, South Korea: implication for modification of intraplate deep-seated rocks[J]. Mineralogy & Petrology, 2012, 106(1-2):107-130.
[4] Dingding, Du, Yanning, et al. Zircon U-Pb dating, whole-rock and Sr-Nd isotope geochemistry of the Reshian granite gneiss of Indian Shield in Jhelum Valley, Lesser Himalayas (Azad Kashmir, Pakistan)[J]. Arabian Journal of Geosciences, 2019, 12(21):1-18.
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