IGNEOUS ROCKS CLAN

1. Feldspathoidal Mafic Rocks2. Non-Feldspathoidal Basic Rocks3. Lamprophyres and Ultrabasic Rocks4. Silica-Saturated Intermediate Rocks5. Acid Rocks6. Feldspathoidal Felsic Rocks

1. Non-Feldspathoidal Basic Rocks

General Characteristics :- Mineralogi : kombinasi plagioklas (An80-

An50), pyroxene (augites and magnesian varieties), magnesian olivines, iron-titanium oxides.

- Colour Index : >40, dark in handspecimen- Silica Content : 45%-52%- Volcanic division : basalt- Plutonic division : gabbro

• A. Volcanic Division : Basalt and DiabaseDiabas : medium grain, tekstur ophitic /subophitic

Basalt Diabas

• B. Plutonic Division (gabbro, Norites, Troctolites, Anorthosites, Pyroxenite)

- Gabbro : plagioklas, diopsid augit, olivine and hornblende- Norites : plagioklas, hypersten, kadang-kadang augit dan olivin- Troctolite : plagioklas , olivin- Anorthosite : plagioklas dominan, minor hypersten or augit- Magnesian and calcmagnesian pyroxenite : magnesian orthopyroxene,or diopsisidic clinopyroxene.

Anorthosit •Troctolite

Gabro Norite

2. FELDSPATHOIDAL MAFIC ROCK

• A. Volcanic Division (Trachybasalt, basanite, tephrite, nephelinite, leucitite)

Nephelinite •Leucitite

• B. Plutonic Division : Feldspathoidal Gabbro , Ijolite1. Feldspathoidal Gabbro :- Sama seperti gabbro pada umumnya, tetapi

mempunyai kandungan feldspathoid sebagai unsur yang essensial.

- Merupakan versi plutonik dari trachybasalt / basanite.

- Dua anggota feldspathoid gabro yang penting adalah Essexite (nepheline monzogabro) dan Theralite (nepheline gabro).

a. Essexite- Mineralogi : sodic orthoclase, plagioklas (An60-

An35), nepheline, mafic mineral (augit), kadang-kadang dijumpai hornblende, biotit sebagai mineral asssori. Mineral assesori minor berupa apatit, sphene, magnetit. Olivin sangat jarang dijumpai.

b. Theralite- Mineralogi : alkali feldspar lebih sedikit dibanding

dengan Essexite. Olivin dijumpai dengan jumlah melimpah.

• 2. Ijolite - Merupakan batuan plutonik dengan kandungan SiO2 < 45%,

miskin feldspar, dengan komposisi utama berupa piroxene dan feldspathoid (nepheline)

. Ijolite. Ijolite

3. Lamprophyres and Ultrabasic Rocks

A. Lamprophyre

B. Melilite-rich rocks

C. Carbonatites

D. Kimberlite

E. Peridotite

A. lamprophyre• Lamprophyre : merupakan istilah yang digunakan untuk menyebut suatu kelompok batuan beku basic-ultrabasic, berwarna gelap, yang pada umumnya terbentuk pada dyke dangkal.

• Ciri utamanya adalah tekstur, dimana sebagian besar lamprophyre bertekstur porfiritik (fenokris biotit, amphibole, augit dan groundmass feldspar). Baik fenokris maupun groundmass berbentuk euhedral (oleh beberapa ahli disebut tekstur panidiomorfik).

B. MELILITIC ROCK

i. Alnoites- SiO2 content :<25%- Asosiasi :nepheline syenite, ijolite- Mineralogi : fenokris biotit (with or without

olivine) in groundmass of melilite, carbonate, perovskite

ii. Melilites- SiO2 content : 30-35%- Volcanic rock, with abundant of melilite and

olivine, but lack of feldspar or feldspathoid.

C. CARBONATITES- Merupakan batuan beku yang terutama

tersusun oleh carbonat (calcite, dolomite, ankerite)

- Tekstur dan kenampakan umum, mirip dengan marble.

- Asosiasi : with basic or ultrabasic alkaline rock (ijolite and alkaline pyroxenite)

- Mineralogi : calcite, dolomite, ankerite, with biotite, olivine, alkali feldspar, sodic pyroxene

Carbonatit

Kimberlite

• Kimberlite is a gas-rich, potassic ultramafic igneous rock that contains the minerals olivine, phlogopite, diopside, serpentine, calcite, and minor amounts of apatite, magnetite, chromite, garnet, diamond, and other upper mantle minerals.

• Kimberlite was named for the rock associated with diamonds in Kimberley, South Africa.

E. Peridotite and allied rock

i. Peridotite- Umumnya bertekstur holocrystalin,

anhedral-granular, medium to coarse grain.- Mineralogi : olivin, pyroxene (enstatite and

diposidic augite),with plagioclase, hornblende, biotite, garnet.

ii. Dunite- Tersusun oleh olivin

iii. Pyroxene peridotit- Wehrlite : olivine and diposidic augite (3:1) assesori : enstatite, picotite, chromite, hornblende- Harzburgite : magnesian olivine and orthopyroxene

(enstatite, bronzite). Asesori : chromite, iron-titanium oxide, diopsidic augit, calcic plagioclas

- Lherzolite :Lherzolites contain over 60% olivine, and some clinopyroxene and orthopyroxene. Lherzolite is a major constituent of the mantle and the source of most basaltic magmas.

4. FELDSPATHOIDAL FELSIC ROCKA. Volcanic Division : Phonolite FamilyIt consists mainly of nepheline and alkali feldspar

(sanidine or anorthoclase). Other minerals occuring in phonolite are soda-pyroxenes, soda-amphiboles, leucite, alcime and sodalite-group minerals (sodalite, nosean, hauyne). It is the volcanic equivalent of nepheline syenite.

B. Plutonic Division : Feldspathoidal Syenite family- Alkali feldspar & feldspathoid sebagai penyusun

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