Quiz 2 (Mineral Groups, Volcanoes, Igneous, Sedimentary, Metamorphic Rocks) Flashcards
Mineral
Inorganic naturally occurring solid with an ordered crystalline structure and defined chemical composition
Most abundant elements in minerals
(O, Si, Al, Fe) Ca, Mg, Na, K
Silicates (mineral group)
Most common mineral at Earth’s surface, links or chains of SiO4, igneous - form directly from cooling of magma or lava
Evaporites (mineral group)
Precipitated by the evaporation of an aqueous solution, salts
Sulfides (mineral group)
Precipitate out of hot hydrothermal vents, contains sulfide ion SiO2, source of many economical metals
How to classify minerals
Luster, hardness, cleavage/ fracture, reacts with acid
Luster
The way a mineral reflects light (metallic or nonmetallic)
Hardness
Resistance to being scratched
Cleavage
Minerals breaks on planar surfaces due to weaker bonds, number of cleavages depends on structure of element, cleavage planes will reflect light the same (same angle) across surface
Fracture
If all bonds are the same strength, there will be no preferred orientation. Fractures will occur in an irregular manner, each surface reflects light independently
Streak
More reliable than color, done by rubbing sample on streak plate, most useful in identifying metallic minerals
Reaction with Acid
CaCo3 is bonded ionically, so when acid is added the Ca and Co disassociate.
Striations
Parallel lines on cleavage surface, useful when distinguishing plagioclase from potassium feldspar (no striations)
Extrusive
Cooled on the surface, fast cooling, fine-grained
Intrusive
Cooled in the crust, slow cooling, coarse-grained
Texture
Size, shape and arrangement of grains
Pegmatite
Very coarse-grained rock, formed when magma cools very slowly at depth
Glassy texture
No crystals, cooled very quickly
Porphyritic
Two crystal sizes
Frothy texture
Bubble chambers (vesicles)
Pyroclastic texture
Formed as a result of magma cooling in the air (volcanic ash, volcanic bombs)
Mafic
Dark-colored, at divergent boundaries where there is increased heat flow and decompression melting
Felsic
Light-colored, at convergent boundaries where there is high pressure & high temps & water release melting occurs above subduction zones
Intermediate
Between light and dark, at convergent boundaries
Intraplate volcanism (hot spots)
Produced by rising mantle plumes, oceanic hot spots = mafic rocks, continental hot spots = felsic rocks
Igneous rock
Rock that forms when hot molten rock (magma or lava) cools and becomes solid
Magma
Hot molten rock beneath Earth’s surface which includes suspended minerals and dissolved gases
Lava
Magma exposed at Earth’s surface
Phaneretic
Igneous rock texture, can be seen with naked eye, intrusive
Aphanitic
Igneous rock texture, crystals are too small to see or rock is glass, extrusive
Porphyritic
Igneous rock texture, large crystals in fine-grained matrix, two (or more) stage cooling history
Pegmatitic
Crystals larger than 2 cm on average, intrusive but rare
Mineral forms
Single, chains, double chains, sheets, 3D
Extrusive equivalent to granite
rhyolite
Extrusive equivalent to granodiorite
dacite
Extrusive equivalent to diorite
andesite
Extrusive equivalent to gabbro
basalt
Where rock melts
Mantle plume and hot spot volcano, subduction zone (yields volcanic arc), beneath a mid-ocean ridge
Dykes (magmatic intrusion)
Vertical sheets
Sills (magmatic intrusion)
Horizontal sheets
Necks (magmatic intrusion)
Near-vertical conduits
Laccoliths (magmatic intrusion)
Wart-like bumps
Plutons & batholiths (magmatic intrusion)
Huge bodies
Shield volcano
Low sloping, usually basaltic, nonexplosive
Strato volanco
Mixed rock and tephra, steep-sided, explosive
Tephra
Unconsolidated accumulations of pyroclastic grains (pieces of rock blown from volcano during eruption)
Pieces of rock blown from a volcano during eruption
Ash, lapilli (marble size), bombs (large)
Tuff
Rock consisting of welded pyroclastic material (pieces are bound together)
Clastic sediments
Broken pieces, clay to boulder size
Chemical
Precipitated from water
Biogenic
Shells and casts of organisms
2 settings that result in large sedimentary basins
Subduction zones, continental rift zones
Graded bedding
Coarse up to fine sediment, deposition from water
Cross bedding
Bedding planes not parallel to stratification, deposition from moving water or air
Lithification
Compaction from deposition and burial, reduction in porosity, cementation
Classification of clastics (biggest to smallest)
Gravel, sand, silt, clay
Metamorphism
The process of changing the characteristics of a rock by changes in pressure and temperature, alters mineral and texture but not composition and no melting
