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BUMI TEMPAT KITA
BERPIJAK
BENTUK DAN STRUKTUR BUMI
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BUMI DAN ALAM SEMESTA
Bumi adalah salah satu unit cakrawaladari sistem tata surya kita, yang terdapat
matahari, planet, dan satelit
Dalam mempelajari geokimiapengenalan kandungan dan komposisi
bumi sangat penting
Bertambahnya kedalaman berubah sifatfisik dan kimianya
Faktor Tekanan dan Temperatur sangat
menentukan komposisi bumi bagian
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Bumi kita tersusun oleh tiga bagian
besar mantel, inti luar dan inti bagiandalam
Kerak samudra berbeda secara
komposisi juga berat jenisnya dengansamudra
Kerak samudra bersifat basalatis dan
bersifat SIMA Kerak benua bersifat granitis dan
bersifat SIAL
Mantel kaya akan besi, Aluminium,
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Struktur Bumi
Nama Sifat Kimia Sifat Fisik
Atmosfir O2,H2O,CO2,
N2
Gas
Biosfer H2O, bahanOrganik
Cairan, Padatan
Hidrosfe
r
Air tawar, Air
Asin
Cairan, Padatan
Kerak Batuan Silikat Padatan
Mantel Bahan Silikat, >
Olivin, Piroksin
Padat
Teras Campuran besi Cairan, Padatan
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STRUKTUR BUMI, RINGWORD,1975KEDALAMAN NAMA BAGIAN SUSUNAN BATUAN
20-25 km
dibawah kerak
Benua
Kerak bumi Bataun beku,
sedimen, metamorf
10-12 km
dibawah kerak
Samudra
Kerak bumi Bataun beku, sedimen,
metamorf
400 km Selubung atas Eklogit dan Peridotit
Kaya Fe,Mg,Ca, Na,
Silikat Al
400-1000 km Jalur peralihan Silikat besi padat, Mg,Ca, Al, Oksida besi
1000-2900 km Selubung bawah Oksida besi padat,
Mg,SiO2
2900-5100 km Inti luar Besi sedikit silikat
5100-6371 km Inti dalam Besi padat
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MOHO - ~40km
Wiechert-
Gutenberg
discontinuity
CRUST
CORE
3 Major Zones, 2 Transitions
Earths Chemical Differentiation
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Mantle Composition
Oxides Mantle Crust
SiO2 45 60
MgO 37 4
FeO 8 4
Al2O3 3 15
CaO 3 6
Na2O 0.5 3Cr2O3 0.4 0.01
MnO 0.2 0.1
TiO2 0.1 1
Mantle makes up >2/3 of earths
mass
Composition approximated by
pyrolite, an invention ofRingwoods to explain the way
these waves move through the
mantle.
SiO2 45%
MgO 30-40%FeO 8-13%
Al2O3 3%
CaO 3%
High Mn, Cr, Ti
Mantle versus crust
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MAGMATIC DIFFERENTIATION
Differentiation processes affect all major rock types. Wide variety of specificreactions happen as igneous, metamorphic, and sedimentary rocks form,change, transport ions, and decompose which result in geochemicaldifferentiation.
How does Magma composition change?
Hot material in different parts of the mantle?
Melts some rocks into itinteracts with surrounding material (PartialMelting)
Fractional crystallizationcrystals form and get separated form
source.
Why earths crust has widely varyingchemistry?
Liqu id
MagmaFractional crystallization
Residual melt
Crystal l ized
rock
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Plate Tectonics - Igneous Genesis
1. Mid-ocean Ridges2. Intracontinental Rifts
3. Island Arcs
4. Active Continental
Margins
5. Back-arc Basins
6. Ocean Island Basalts7. Miscellaneous Intra-
Continental Activity
kimberlites,
carbonatites,
anorthosites,
etc.
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Trace elements and partition coefficients
Definition: a trace elementis an element present at concentration too low tosignificantly affect the phase relations; hence it is a passive agent in the
processes determined by the major and minor elements. In particular thebehavior of the trace element does not depend on its own concentration(Henrys Law).
To use trace elements, we need to know how they are distributed, orpartitioned, among phases. Most often this is expressed by looking at theratio of concentration in a solid phase to concentration in the liquid phase,thepartition coefficient
Dimineral/melt
i mineral
i melt
Di f j
j
Dij /melt
When several minerals are present in the rock, then we can find the bulkpartition coefficientby a suitable weighted average of mineral partition
coefficients:
If the bulk partition coefficient < 1, the trace element is termed
incompatible.If the bulk partition coefficient > 1, the trace element is compatible
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Nuclear reactions
determine element
abundance
Is the earth
homogeneousthough?
Is the solar system??
Is the universe???
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