Igneous Rocks -- II Intermediate Rocks Acidic Rocks

Classifications: minerals & chemical compositions

Intermediate Rocks TextureAlkali feldspar < 1/3 Alkali feldspar >1/3 < 2/3 Alkali feldspar >2/3 Feldspathoidal Volcanic rocks AndesiteTrachyandesite (latite) TrachytePhonolite Plutonic rocks DioriteMonzoniteSyeniteFeldspathoidal syenite

Diorite Definition: is intrusive, holocryatalline, phaneritic, containing: Plagioclase (oligoclase or andesine) ~70% Mafic (commomly hornblende or biotite) ~25%

Diorite: Plag+ Mafic ( Hb, Cpx, Bi)

Trachytoid Diorite

Andesite Definition: is volcanic and hypabyssal intrusive, holocryatalline or hypocrystalline, with matrix aphanetic, containing: Plagioclase (oligoclase or andesine) ~70% Mafic (commomly hornblende or biotite) ~25%

Andesite: Plag+Mafic (Cpx, Hb, Bi)

Porphyritic Andesite

High-Mg andesite: Plag+Opx+Ol

Tonolite (quartz andesite) Definition: is intrusive, plutonic and hypabyssal, holocryatalline, phaneritic, containing: Sodic plagioclase (oligoclase or andesine) ~80% Quartz ~10% Mafic (biotite and hornblende) ~10%

Tonalite: Plag+Mafic (Bi, Hb) +quartz (< 10%)

Dacite (quartz andesite) Definition: is volcanic and hypabyssal intrusive, holocryatalline or hypocrystalline, with matrix aphanetic, containing: Sodic plagioclase (oligoclase or andesine) ~80% Quartz ~10% Mafic (biotite and hornblende) ~10%

Dacite: Plag+Mafic (Bi, Hb) +quartz (< 10%)

Monzonite Definition: is intrusive, Plutonic or hypabyssal, holocryatalline, phaneritic, containing: Mafic (hornblende, biotite, augite) ~60% Sodic Plagioclase (oligoclase or andesine) ~30% Potash feldspar (orthoclase) ~25%

Monzonite: Plag+K-feldspar +Mafic (Bi, Hb, Aug)

Latite Definition: is volcanic and hypabyssal intrusive, holocryatalline or hypocrystalline, with matrix aphanetic, containing: Mafic (hornblende, biotite, augite) ~60% Sodic Plagioclase (oligoclase or andesine) ~30% Potash feldspar (orthoclase) ~25%

Syenite Definition: is intrusive, Plutonic or hypabyssal, holocryatalline, phaneritic, containing: Alkali feldspar (orthoclase) ~80% Sodic Plagioclase (oligoclase or andesine) ~25% Mafic (hornblende, biotite, augite) ~10%

Syenite: K-feldspar+ Plag +Mafic (Bi, Hb, Px)

Trachyte Definition: is volcanic and hypabyssal intrusive, holocryatalline or hypocrystalline, with matrix aphanetic, containing: Alkali feldspar (orthoclase) ~80% Sodic Plagioclase (oligoclase or andesine) ~25% Mafic (hornblende, biotite, augite) ~10%

Trachyte: K-feldspar+ Plag +Mafic (Bi, Hb, Px)

Acidic rocks or Silicic Rocks Granite Rhyolite Granodiorite Quartz latite

Granite Definition: is plutonic, intrusive, and hypabyssal, holocryatalline, phaneritic, containing: Quartz ~40% Potash feldspar ~60% Sodic plagioclase (excluding perthite) ~35% Mafic (biotite, hornblende) ~25%

Calc-alkali granite Perthitic orthoclase or microcline Oligoclase or rarely andesine Hornblende Diopside or augite Alkali granite Strongly perthite orthoclase or microcline, anorthoclase Albite or sodic oligoclase Iron-rich biotite Hastingsite, arfvedsonite, riebeckite Aegirine-augite, rarely hedbergite

Granite

Granite: Or + Qz + Mica (Bi, Mus)

Microcline

Perthite

Alkali granite: Or + Qz + Alkali Hb

Rhyolite Definition: is volcanic and hypabyssal, holocryatalline or hypocrystalline, with matrix aphanetic, containing: Quartz ~40% Potash feldspar ~60% Sodic plagioclase (excluding perthite) ~35% Mafic (biotite, hornblende) ~25%

Rhyolite

Obsidian

Rhyolite: Or + Qz

Rhyolite: Or + Qz

Pumice

Granodiorite Definition: is plutonic and intrusive, holocryatalline, phaneritic, containing: Potash feldspar ~40% Sodic plagioclase ~45% Quartz ~10% Mafic (biotite, hornblende) ~10%

Granodiorite: Or + Plag + Qz + Mafic (Bi, Hb)

Granodiorite: Or + Plag + Qz + Mafic (Bi, Hb)

Quartz latite Definition: is volcanic and hypabyssal, holocryatalline or vitrous, with matrix aphanetic, containing: Potash feldspar ~30% Sodic plagioclase ~50% Quartz ~10% Mafic (biotite, hornblende) ~10%

Ultrabasic and basic rocks

Classifications: minerals & chemical compositions

Definition Peridotite is holocrystalline, phaneritic, plutonic rocks; containing Mafic (Ol, Px, Hb) % Ores (magnetite, ilmenite, chromite) % Calcic plagioclase < 5%

Classification Peridotite ---- group name Ol Dunite Ol + OPX (En or Hy) ----Harzburgite Ol + CPX (aug) Wehrite Ol + OPX + CPX ---- Lherzolite Ol + Hb Cortlandtite Px (CPX + OPX) Pyroxenite Hb Hornblendite Kimberlite --- mica peridotite

Dunite — olivine + chromium-rich spinel

Harbuzite — Olivine + OPX

Wehrite — Olivine + CPX

Lherzolite — Olivine + OPX + CPX

Garnet peridotite

Pyroxenite--- CPX + OPX

Hornblendite- -- Hb

Kimberlite --- mica peridotite

Fine-grained ultramafic rocks Komatiite ankaramite --- Diopside augite Limburgite --- Augite Katungite --- melilite-rich Ol leucitite Ugandite --- melanocratic Ol leucitite Melilitite & nephelinitite --- nepheline basalt Basanite

Komatiite

Leucitite

Meymechite

Basanite

Ultramafic vs. Ultrabasic Mafic mineral: > 70% Ultramafic  ultrabasic SiO2 < 45 wt% Ultrabasic ~ ultramafic Ex. Carbonatite, anorthosite

Carbonatite

Basic rocks Volcanic rocks: Tholeiite: Cpx+Plag Alkali basalts: Plag+Cpx+Ol Picrite: Ol  Plag Plutonic Rocks Diabase Gabbro: Plag + Cpx Norite: Plag + Opx Eucrite: Calcic Plag + Opx Troctolite: Ol +Plag Anorthosite: Plag  Mafic

Gabbro Definition: is intrusive, plutonic, holocrystalline, phaneritic rocks. Containing: Mafic (aug, Hy, or Ol less commomly Hb) % Plagioclase (labradonite or bytownite) %

Classifications Gabbro --- Aug + Calcic Plag Ol-gabbro --- Aug + Ol + Calcic Plag Troctolite --- Ol + Calcic Plag Norite --- Hy + Calcic Plag Anorthosite --- Ol + Calcic Plag

Diabase (dolerite) Definition: is intrusive, hypabyssal, normally holocrystalline Containing Mafic (aug, Hy, less commomly Ol) % Plagioclase (labradonite or bytownite) %

Basalts Definition: is volcanic and uncommonly hypabyssal intrusive, holocrystalline, hypocrystalline rarely vitrous matrix aphanitic. Containing Plagioclase (labradonite) % Mafic (aug, Ol) %

Tholeiitic basalt: Cpx  Plag ± Ol

Alkali basalt: Plag + Ol  Cpx

Lunar low-Ti basalt: Plag + Ol  Cpx

Lunar high-Ti basalt: Plag  Cpx ± Ol

Picrite basalt: Ol  Cpx±Plag

Glassy groundmass

Vesiculated basalt

Gabbro: Plag+Cpx

Alkali gabbro: Plag+Cpx±Ol

Alkali Gabbro: Plag+Ol+Cpx±K- feldspar or ±Feldspathoid

Basic dike rocks Diabase

Norite: Plag+Opx

Anorthosite: Plag ± Mafic (< 10%)