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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???