TOPIC 1B classification

Classification of Igneous Rocks: 

TOPIC 1 Classification of Igneous Rocks 1

Overview: 

Overview Basis for classification schemes of igneous rocks Textures: volcanic versus plutonic Chemical Composition: reflected by mineralogy; often used for volcanic rock classification using whole rock analysis Mineralogical (modal) classification of igneous rocks; most rock types consist of 4-7 main minerals Pyroclastic rocks: made up of fragments 2

IUGS CLASSIFICATION SYSTEM: 

3 IUGS CLASSIFICATION SYSTEM Qtz -rich granitoid Granite Tonalite Qtz monzodiorite Monzodiorite Granodiorite Quartzolite Alkali feldspar granite Tonalite Alkali feldspar Qtz syenite Alkali feldspar syenite Quartz syenite Syenite Monzonite Qtz diorite Diorite Gabbro Anorthosite Plutonic rocks

Alkali Granite: 

Description A felsic igneous rock from the bottom of Bowen's Reaction Series. Typically light colored (few mafic minerals) with orthoclase the most obvious mineral (typically pink but also white or greenish), but quartz >20% is essential. This rock can be confused with a syenite which appears superficially similar. The amount of quartz is the key: <20% and the rock is "quartz syenite". Typical Minerals QUARTZ > 20% ORTHOCLASE is greater than Plagioclase Mafics < 10% Alkali Granite 4

Alkali Granite (cont.): 

Alkali Granite (cont.) Tectonic Association Granite, as with all felsic rocks, is found on continents . It is one of the last fractionation products and typically results from partial melting of the lower crust . Granite porphyry Locations: 5

Alkali Granite (cont.): 

Alkali Granite (cont.) 6 Field occurrence As various forms in field

Plagio-granite (Tonalite): 

Plagio-granite (Tonalite) Description A felsic igneous rock from the bottom of Bowen's Reaction Series. Typically light colored (few mafic minerals) with sodium plagioclase the most obvious mineral, but quartz >20% is essential. Orthoclase can be present in plagio-granite. Muscovite it not common in most igneous rocks but this specimen has some; it appears brassy and shiny. This rock can be confused with a monzonite which appears superficially similar. The amount of quartz is the key: <20% and the rock is " quartz monzonite ". Watch the mafics; if they exceed 10% then the rock is heading toward a diorite or granodiorite . Another common name for plagio-granite is tonalite . Typical Minerals QUARTZ > 20% PLAGIOCLASE is greater than Orthoclase Mafics - < 10% (here < 5%) MUSCOVITE - trace (brassy looking) 7

Plagio-granite (Tonalite) (cont.): 

Plagio-granite (Tonalite) (cont.) Tectonic Association Plagio-granite, is the result of fractional melting above a rapid subduction zone . It is commonly produced in volcanic arcs , and in cordilleran mountain building (subduction along the edge of a continent, such as with the Andes Mountains). Plagio-granite is a common component of the cores (cratons) of continents , especially the most ancient portions which were constructed from numerous small volcanic arcs with rapid subduction in the Earth's earliest, hottest phases. 8

Syenite: 

Syenite Typical Minerals ORTHOCLASE - 65-100% Plagioclase - 0-35% Mafics - < 10% Quartz - 0-5% Description A felsic igneous rock from the bottom of Bowen's Reaction Series. Typically light colored (few mafic minerals) with pink orthoclase being the most obvious mineral (although it can be white or greenish). Quartz is sometimes present but if it is between 5 and 20% the rock is a "quartz syenite." If quartz exceeds 20% the rock shifts into the alkali granite category. Tectonic Association Syenite, as with all felsic rocks, is found on continents . It is one of the last fractionation products and typically results from partial melting of the lower crust . 9

Monzonite: 

Typical Minerals PLAGIOCLASE: 35-65% Orthoclase: 35-65% Mafics: < 10% (commonly <5%) Quartz: 0-5% Description Monzonite is one of three rocks dominated by feldspar (the others being anorthosite and syenite ) with occasional other minerals thrown in in lesser amounts. The plagioclase is sodium rich , unlike anorthosite which is calcium rich. Because monzonite is light colored it is often confused with granite but granite has quartz >20%. Monzonites with quartz 5-20% are "quartz monzonites." Less than 5% quartz and the rock is just monzonite. 10 Monzonite

Monzonite (cont.): 

Monzonite (cont.) Tectonic Association Monzonite is not a common rock, but is typically found around the edges of other felsic plutons , such as plagio-granites or granodiorites. It is typical of continents . 11

Anorthosite: 

Anorthosite Typical Minerals The rock anorthosite is named after the mineral anorthite - Calcium rich plagioclase. Anorthosite occasionally has pyroxene associated with it, but less than 10%. Description Anorthosite is an unusual rock , not only because it is composed only of calcium plagioclase , but also because it is relatively rare , and forms by mechanisms we do not fully understand. Anorthosite is common on the moon. Typically when we find anorthosite it is in large masses covering hundreds of square km at least. 12

Anorthosite (cont.): 

Anorthosite (cont.) Tectonic Association Although anorthosite was probably common in the early history of the earth it has become less and less common through time. Little if any is forming today in places we can see. Anorthosite seems to be associated with rifting events , but there is a good likelihood that more than one mechanism is responsible for its formation. 13

Granodiorite: 

Granodiorite Typical Minerals Na/Ca Plagioclase: ~50% Quartz: > 20% Amphibole/Biotite: 10-25% Orthoclase: 10-35% in QAP 14

Granodiorite: 

Granodiorite Description This is a mixed rock . It has a high quartz content, like a granite, but also a high mafic (amphibole/biotite) content (10-25%) more like a diorite. Granodiorite is typically intermediate colored with a mixture of light colored Na-Ca plagioclase/quartz, and dark colored amphibole and biotite. Appearance, like diorite, is often described as "salt and pepper" because of the mix. Orthoclase may be present in small amounts. Tectonic Association Granodiorite, like diorite, is the result of fractional melting of a mafic parent rock above a subduction zone . It is commonly produced in volcanic arcs , and in cordilleran mountain building (subduction along the edge of a continent, such as with the Andes Mountains). It emplaces in large batholiths (many thousands of square km) and sends magma to the surface to produce composite volcanoes with andesitic lavas . 15

Diorite: 

Diorite Description An intermediate igneous rock from the middle of Bowen's Reaction Series. Color: Speckled black and white in hand specimen; occasionally shades of dark green or pink. The dark minerals are more noticeable than in gabbro. Typically intermediate colored with a subequal mixture of light colored Na-Ca plagioclase and dark colored amphibole ( biotite may also be present). Appearance is often described as " salt and pepper " because of the mix. Quartz: 0-5% diorite, 5-20% Qtz diorite, >20% granodiorite What keeps this from then being a monzonite is the high mafic content ; monzonites have commonly less than 5% mafics . 16

Diorite: 

Diorite Typical Minerals Essentially plagioclase (oligoclase or andesine) and hornblende; Na/Ca Plagioclase & Mafic minerals ( amphibole ) about 50/50 Biotite and/or pyroxene may occur . Alkali feldspar and quartz (quartz diorites) may be present, when diorite grades into granodiorite. Common accessory minerals are apatite, sphene and iron oxides . Grain size: fine to coarse; may be pegmatitic. 17

Diorite: 

Diorite Texture Equigranular or porphyritic . In porphyritic varieties the feldspar or hornblende may form phenocrysts . Diorites often vary rapidly in texture; an equigranular variety may grade into a porphyritic one within a few centimeters. They are sometimes foliated due to the roughly parallel arrangement of the minerals . Structure: Xenoliths are common. Field relations Forms independent stocks and dykes , Transition : also comprises local variants of masses of granite , and sometimes gabbro , into which they merge imperceptibly." 18

Diorite: 

Diorite Tectonic Association Diorite is the result of fractional melting of a mafic parent rock above a subduction zone . It is commonly produced in volcanic arcs , and in cordilleran mountain building (subduction along the edge of a continent, such as with the Andes Mountains). It emplaces in large batholiths (many thousands of square km) and sends magma to the surface to produce composite volcanoes with andesite lavas . 19

IUGS CLASSIFICATION SYSTEM: 

Plutonic Gabbroic Rocks Ultramafic rocks 20 IUGS CLASSIFICATION SYSTEM Figure 2.2b. A classification of the phaneritic igneous rocks: Gabbroic rocks. After IUGS.

Gabbro: 

Gabbro Description A mafic igneous rock from the top of Bowen's Reaction Series. Typically dark colored with a mixture of dark gray calcium plagioclase and dark colored (dark green to black; dull; not showing good cleavage) pyroxene . Although the plagioclase may be dark gray it can also be light gray (as in this specimen) or even white. What is critical here is the prominence of pyroxene from the top of Bowen's Reaction series, although it may be mixed with amphibole . Olivine is sometime present but is not essential . 21

Gabbro: 

Gabbro Typical Minerals Ca PLAGIOCLASE & PYROXENE about 50/50 Amphibole often present Olivine - absent to trace Because the feldspars are light colored and have more time to grow in intrusive rocks, gabbros tend to be dark with gray or white speckles. Gabbros are less abundant on the continents because they tend to form in the lower part of the oceanic crust. Occurrence As xenolith within felsic rocks As dykes As plutons 22

Gabbro: 

Gabbro Tectonic Association Gabbro is typically found on continents in dikes, sills, and laccoliths from slow cooling of mafic magma, mostly derived from hot spots . Gabbro is also part of the oceanic lithosphere ( ophiolite suite ) forming as a thick layer below the top-most pillow lavas across all the oceanic floors. 23

Diabase (dolerite): 

Diabase (dolerite) Color When fresh it is black, dark-grey or green; may be mottled black and white. Structure Vesicles and amygdales occur. Sometimes has segregations of coarser rock enriched in feldspar. Mineralogy: Phenocrysts comprise olivine (olivine diabase ) and/or pyroxene or plagioclase . The groundmass comprises the same minerals with iron oxide, and sometimes with some quartz, hornblende or biotite . Texture Occasionally ophitic texture can be distinguished in hand specimen. May be porphyritic . Grain size Medium. Field relations Dykes and sills. These may form swarms of hundreds or perhaps thousands of individual dykes or sills which often radiate from a single volcanic center." 24

PowerPoint Presentation: 

Quiz: … and … are ultramafic and sialic, respectively. Monzonite, trachyte Komatiite, rhyolite Peridotite, dacite Basalt, syenite X 25

PowerPoint Presentation: 

Quiz: The amount of water …. and Na-K …. from mafic to felsic rocks. increase, decrease decrease, increase decrease, decrease increase, increase X 26

PowerPoint Presentation: 

Quiz: Which group of igneous rocks would be common in the continental crust? Granitic, andesitic Andesitic, basaltic Basaltic, ultramafic Rhyolitic, ultramafic X 27

PowerPoint Presentation: 

Quiz: Continental rifting would be a suitable environment to form: gabbro basalt dunite diabase Syenite X 28

PowerPoint Presentation: 

Quiz: Which rock has more quartz compared to others? Quartz monzonite granodiorite Quartz syenite Quartz diorite X 29

PowerPoint Presentation: 

Quiz: Which rock would commonly form in the continental craton? gabbro andesite harzburgite dunite syenite X 30

PowerPoint Presentation: 

Quiz: Which rock would have more sodic plagioclase? gabbro andesite harzburgite Dunite tonalite X 31

PowerPoint Presentation: 

Quiz: Which rock has more K-feldspar than the other rocks? rhyolite dacite andesite Basalt Syenite X 32

IUGS CLASSIFICATION SYSTEM: 

Plutonic Ultramafic rocks 33 IUGS CLASSIFICATION SYSTEM Figure 2.2c. A classification of the phaneritic igneous rocks: Ultramafic rocks. After IUGS.

Dunite: 

Dunite Description An ultramafic igneous rock from the top left side of Bowen's Reaction Series. Typically pale green (olive green) in granular masses. Massive varieties sometimes exist. What is notable about the rock is the absence of feldspars of any kind. Feldspars are so common (some 56% of the earth's crust) that when they are absent it says something special is going on. 34

Dunite: 

Dunite Typical Minerals OLIVINE >90% Pyroxene may be present, as well as black chromite crystals. NO feldspars! Tectonic Association Dunite (and peridotite) is typically found on continents in dikes, sills, and laccoliths associated with mafic igneous bodies . The concentration of olivine may occur through gravity settling , as well as other mechanisms. Dunite/peridotite is also a common constituent of the oceanic lithosphere (ophiolite suite) forming below the crust in the mantle (below the Moho boundary). 35

IUGS CLASSIFICATION SYSTEM: 

IUGS CLASSIFICATION SYSTEM Figure 2-3 . A classification and nomenclature of volcanic rocks. After IUGS. Volcanic rocks 36 Rhyolite Andesite Basalt

Rhyolite: 

Rhyolite Color Usually light colored ; white, grey, greenish, reddish or brownish. The color may be even, or in bands of differing shades. Typical Minerals Minerals too small to identify (except phenocrysts ). Composition will be from bottom of Bowen's Reaction series (i.e. felsic ). Grain size: Fine to very fine. In this detail no crystals can be seen (except for a few small fragments) indicating the rapid cooling history of this rock. Rhyolite porphyry 37

Rhyolite: 

Rhyolite Texture Frequently shows altering layers that differ slightly in granularity or color. Phenocrysts not uncommon ( porphyritic rhyolite ). Flow banding is sometimes evident, defined by swirling layers of differing color or granularity, and by aligned phenocrysts. 38

Rhyolite: 

Rhyolite Structure Vesicles or amygdales may be present. Pumice is the highly vesicular variety of rhyolite. May contain spherulites which are spherical bodies, often coalescing, comprising radial aggregates of needles , usually of quartz or feldspar. Spherulites are generally less than 0.5 cm in diameter, but they may reach a meter or more across. Spherulites form by very rapid growth in quickly cooling magma, and the crystallization of glass . Mineralogy: As for granite, but rapid cooling results in minute crystals. Phenocrysts of quartz, feldspar, hornblende or mica occur. 39

Rhyolite: 

Rhyolite Field relations Form as flows, dykes and plugs . Rhyolite (or granite) magma is highly viscous and so flows only very slowly, so that if it is extruded it forms very short, thick flows or is confined as a plug in the throat of a volcano." Volcanic breccia is found with rhyolite. 40

Rhyolite: 

Rhyolite 41

Pumice: 

Pumice Typical Minerals Volcanic Glass. Pumice has cooled too quickly for minerals to form. Chemical composition, however, will be from the bottom of Bowen's Reaction series (i.e. felsic). Detail Description Pumice is a vesicular, foamy, very light weight, light colored rock formed by abundant, rapid gas escape during formation. It is often a pyroclastic product. 42

Obsidian: 

Obsidian Obsidian and pitchstone Color Shiny black, also brown or grey. Pitchstones have a dull rather than a shiny luster. Grain size None; the rock is glassy. Texture: Glassy, but obsidian may contain numerous phenocrysts. Structure May be spotted or flow banded and spherulites (see rhyolite) are common. Being a siliceous glass it breaks with a conchoidal fracture and may be fashioned to a sharp cutting edge. It was used for cutting tools by primitive peoples. Mineralogy Essentially a glass. Rare phenocrysts (abundant in pitchstones) of quartz and feldspar. Field relations Dykes and flows. Commonly associated with rhyolites to which they are chemically equivalent." 43

Obsidian: 

Obsidian Typical Minerals Volcanic Glass resulted from instantaneous cooling. Obsidian has cooled too quickly for minerals to form. Chemical composition, however, will be from the bottom of Bowen's Reaction series (i.e. felsic). Description We typically associate obsidian with very black , shiny , glassy , with conchoidal fracture (smooth curved breaks, often with concentric ridges.) This specimen is the less common red variety. The fact that this is glass means it has no minerals because it cooled too quickly for them to form . Tectonic Association Associated with felsic volcanism on the continents . 44

Andesite : 

Andesite Description A fine grained (aphanitic) igneous rock, medium to dark in color. Color is such a poor indicator of rock identification in most cases, that it can only be a first approximation. Here, however, the amphibole phenocrysts put this specimen in the intermediate range. Typical Minerals Minerals too small to identify (except phenocrysts, which here are amphibole . Composition will be from middle of Bowen's Reaction series, and include such minerals as Ca/Na plagioclase , amphibole , and biotite . 45

Andesite : 

Andesite Tectonic Association Andesite, as with all intermediate rocks, is found principally in volcanic arc systems, either intraoceanic volcanoes (e.g. Japan, Aleutian Islands), or cordilleran systems (Andes mountains). It characteristically forms composite explosive volcanoes. 46

Andesite : 

Andesite 47

Basalt : 

Basalt Color A mafic igneous rock from the top of Bowen's Reaction Series. When fresh it is black or greyish black; often weathers to a reddish or greenish crust. Grain size Fine-grained Texture Usually dense with no minerals identifiable in hand specimen; a freshly broken surface is dull in appearance. May be porphyritic . Structure: Often vesicular and/or amygdaloidal . Xenoliths are relatively common and usually consists of olivine and pyroxene; they have a green color. Columnar jointing is common and often spectacular. Vesicular (cellular) varieties are quite common, and these grade completely into scoria. 48

Basalt: 

Basalt Mineralogy Minerals too small to identify (except phenocrysts). Olivine is sometime present as phenocrysts but is not essential . Phenocrysts are usually olivine (green, glassy), pyroxene (black, shiny) or plagioclase (white-grey, tabular). If olivine is present the rock is called olivine basalt . Microscopic examination show the groundmass consists of plagioclase ( usually labradorite ), pyroxene, olivine and magnetite , with a wide range of accessory minerals. Amygdales may be filled, or partly filled with zeolites, carbonates or silica, usually in the form of chalcedony or agate. Basalts never contain quartz . Composition will be from the top of Bowen's Reaction series (i.e. mafic) and we would expect Ca plagioclase, pyroxene, and perhaps some olivine. Note that these minerals are present in this specimen, just too small to see. 49

Basalt: 

Basalt Tectonic Association Basalt is one of the most common igneous rocks found. It is the major constituent of the upper layer of the ocean floors (usually as pillow lava ), and hot spot volcanoes (such as the Hawaiian islands). Basalt commonly forms on the continents too, usually the result of hot spot activity . Here it may exist as dikes and sills, or extrusive cinder volcanoes and lava flows . So basalts comprise most of the sea floor and are also common around continental volcanoes. 50

Basalt: 

Basalt Field relations Lava flows and narrow dykes and sills. Chilled margin: The edges of dykes or sills are often finer grained than the centers or even glassy, due to rapid cooling on intrusion. Most basalts occur as lava flows either in volcanoes or as extensive sheets building up a lava plateau, which may cover hundreds of thousands of square kilometers , and may be fed by numerous fissures. The surface forms of lavas are of two principal types; smooth or ropy (the surface looks like a rope) which is known by the Hawaiian term of pahoehoe, and scoriaceous which is rough and clinker and has the Hawaiian name aa. Another common form is pillow lava which consists of pillows or balloon-like masses of basalt - usually with a very fine-grained or glassy outer layer. They are formed by the eruption of lava into water." 51

Basalt: 

Basalt 52

Basalt Porphyry : 

Basalt Porphyry Description A mafic igneous rock from the top of Bowen's Reaction Series. Typically dark colored, as is the aphanitic portion of this rock, although the large plagioclase phenocrysts give it a lighter appearance. The phenocrysts indicate this rock had a two stage cooling. Typical Minerals Minerals too small to identify (except Ca plagioclase phenocrysts). Composition will be from the top of Bowen's Reaction series (i.e. mafic) and we would expect, in addition to Ca plagioclase , pyroxene , and perhaps some olivine . Note that these minerals are present in this specimen, just too small to see. 53

Basalt Porphyry: 

Basalt Porphyry Tectonic Association The large phenocrysts in basalt porphyry tell us it had a two stage cooling , having spent some time below the surface cooling slowly enough for the plagioclase crystals to form, and then being brought toward the surface for rapid cooling. But even the fine grained portion of this rock is more granular than the previous specimen, indicating it probably did not cool at the surface, but perhaps in a dike, sill or laccolith. 54

Vesicular Basalt: 

Vesicular Basalt Description A mafic igneous rock from the top of Bowen's Reaction Series. Typically dark colored, although weathered specimens can appear quite light, or reddish. This vesicular or cellular specimen is full of holes produced when gas expanded as the lava was extruded to the surface. Vesicular varieties vary widely, and grade completely into scoria . Typical Minerals Minerals too small to identify (except phenocrysts). Composition will be from the top of Bowen's Reaction series (i.e. mafic) and we would expect Ca plagioclase, pyroxene, and perhaps some olivine. Note that these minerals are present in this specimen, just too small to see. 55

Vesicular Basalt: 

Vesicular Basalt Tectonic Association Basalt is one of the most common igneous rocks found. It is the major constituent of the upper layer of the ocean floors (usually as pillow lava), and hot spot volcanoes (such as the Hawaiian islands). Vesicular varieties such as this one are typically terrestrial , forming either on volcanic islands or on the continents . Vesicular olivine basalt 56

Scoria: 

Scoria Typical Minerals Scoria has cooled too quickly for minerals to form; i.e. it is volcanic glass . Chemical composition, however, will be from either the middle or top of Bowen's Reaction series (i.e. intermediate or mafic). It is not possible to tell the composition from external appearance alone and so we just spread all scoria across the intermediate to mafic range. If we found it in place it would most likely have the composition of the surrounding rock. Description The very fine vesicles (holes) can be seen even here. The rock is quite light in weight since it is mostly made of holes. 57

Scoria: 

Scoria Tectonic Association Scoria is associated with intermediate and mafic volcanic processes in terrestrial environments , commonly appearing with vesicular basalts in cinder cones and lava flows . 58

Classification of Basalts: 

Classification of Basalts There are two main types of basalts Tholeiite Alkali Olivine Basalt (or alkaline basalt) . Tholeiite versus Alkali Olivine Basalt An essential and critical feature of tholeiites is the reaction relation between olivine and Ca-poor pyroxene , often indicated by pyroxene mantling olivine . In strong contrast, olivine and Ca-rich pyroxene in alkali olivine basalts show a cotectic relationship (i.e., crystallizing simultaneously from the magma ). Alkali Olivine Basalt Tholeiitic Basalt Petrographic Features 59

Classification of Basalts: 

Classification of Basalts Alkaline Basalt (Alkali Olivine Basalt) Tholeiitic Basalt Note: Though common in their respective types of basalts, it is rare to find all of these features in a single rock. Chemical Features______ Normative Ne Normative Hy _____________________ SiO 2 46-48 48-52 TiO 2 2-3 1-2 Al 2 O 3 14-16 14-16 FeO * 4-7 5-7 MgO 5-8 4-6 CaO 8-10 7-10 Na 2 O 2-3 1.5-2.5 K 2 O 0.3-1.5 0.1-1 Stable groundmass olivine Phenocrysts of olivine resorbed and rimmed by pyroxene, none in groundmass Reddish titaniferous pyroxene Augite, hypersthene or pigeonite Interstitial alkali feldspar Interstitial quartz Nepheline or leucite (in basanites ) Plagioclase with sodic rims Vesicles lined with analcime or zeolite Vesicles line with silica mineral 60

Classification of Basalts: 

Classification of Basalts Tholeiite Tholeiite has essential minerals of: Pyroxene : augite (zoned) or subcalcic augite, with pigeonite or hypersthene or both. Pyroxenes exhibit pyroxene exsolution lamellae. Plagioclase : bytownite to labradorite in phenocrysts Iron oxides . Olivine: is present in subordinate amounts or may be absent. Any olivine is out of equilibrium with melt and shows reaction relation with hypersthene phenocrysts or pigeonite in groundmass. Olivine only occurs as phenocrysts in tholeiites (not in groundmass). Tholeiites differentiate to dacite-rhyolite , i.e. quartz in the residual liquid. Inclusion in tholeiites are usually gabbro – no peridotite . 61

Classification of Basalts : 

Classification of Basalts Alkali olivine basalt (Alkaline Basalt) It has essential minerals of: Ca-rich clinopyroxene (Ca > 45 atomic %), The pyroxene is titanaugite (mauve color due to high Ti content, > 2%), no hypersthene or pigeonite is present. Generally tholeiitic pyroxenes are normative hypersthene or quartz bearing whereas alkali olivine basalt have normative nepheline . plagioclase of bytownite to andesine in phenocrysts and labradorite to andesine in the groundmass , Iron oxides. Olivine: It is abundant and occurs as phenocrysts and in the groundmass . It is in equilibrium with the melt, i.e. shows no reaction relation. Interstitial alkali feldspar or nepheline may be present. Normative nepheline and olivine are both present. Alkaline olivine basalt differentiates to trachyte or phonolite – i.e. undersaturated residual liquid . Peridotite + eclogite inclusions are common in alkaline olivine basalt. 62

Classification of Basalts: 

Classification of Basalts Transitional basalt or olivine tholeiite It is the intermediate between alkali olivine basalt and tholeiite. It contains plagioclase ( anorthite to labradorite in phenocrysts and labradorite to andesine in the groundmass ), titaniferous augite , iron oxides, and olivine with reaction relation with the melt. It may have residual interstitial alkali feldspar . It has normative hypersthene and olivine . It differentiates to trachyte or peralkaline residual liquid. 63

PowerPoint Presentation: 

Quiz: A rock contains 50% Na-Ca plagioclase, 25%Qtz and 25% amphibole+biotite. This rock is a: Monzonite Diorite Granodiorite Qtz monzonite X 64

PowerPoint Presentation: 

Quiz: A rock contains 40% Na-Ca plagioclase, 10% Qtz and 50% amphibole+biotite. This rock is a: Monzonite Diorite Granodiorite Qtz monzonite Qtz diorite X 65

PowerPoint Presentation: 

Quiz: The common tectonic setting for diorite is: Subduction zone Hot spots Oceanic crust Hot spots and some oceanic crusts X 66

PowerPoint Presentation: 

Quiz: Olivine is an essential mineral in: gabbro basalt Diorite diabase none X 67

PowerPoint Presentation: 

Quiz: Ophitic texture is common in: gabbro basalt diabase dacite X 68

PowerPoint Presentation: 

Quiz: A rock contains 91% olivine and 9% pyroxene. It is a: gabbro peridotite harzburgite dunite X 69

PowerPoint Presentation: 

Quiz: Pumice and scoria composition is respectively similar to: Dacite-basalt Basalt-dacite Rhyolite-basalt Basalt-andesite X 70

PowerPoint Presentation: 

Quiz: Chemical composition of obsidian is equivalent to: gabbro dacite andesite rhyolite X 71

PowerPoint Presentation: 

Quiz: Which rock type is more likely to form narrow dykes? rhyolite dacite andesite basalt X 72

PowerPoint Presentation: 

Quiz: Rimmed olivine grain by pyroxene is mainly found in: rhyolite dacite andesite Tholeiite Alkali olivine basalt X 73