ROCKS

• a naturally-occurring aggregate of two or more minerals

  rocks
• refers to the study of rocks; its genesis, composition, distribution and structure of rocks

  petrology
• involves examining processes that lead to the formation of rocks, as well as their identification and classification

  petrology
• branch of petrology that deals with the description and classification of rocks; their constituent minerals and texture

  petrography
• explains the processes underwent by rocks on and under the earth's surface

  rock cycle
• formed from cooling of magma

  igneous rocks
• formed when weathered fragments of other rocks are compressed and cemented together

  sedimentary rocks
• precipitation from solution

  sedimentary rocks
• formed by alteration of pre-existing rock

  metamorphic rocks
• temperature ranging from 600 degrees to 1200 degrees celsius

  magma
• molten or partially molten rock composed of varying amounts of: liquid, solids. and dissolved gas or volatiles

  magma
• silicic or acidic (>63% SiO2) continental crust

  felsic
• 52-63% SiO2 continental crust

  intermediate
• 45-52% SiO2 basic

  mafic
• <45% SiO2 ultrabasic

  ultramafic
• property to resist flow

  viscosity
• denser oceanic crust

  mafic rocks
• lighter continental crust

  felsic rocks
• temperature of the melt formation

  temperature
• high density, low viscosity, low silica content

  basaltic magma
• low density, high viscosity, high silica content

  granitic / rhyolitic magma
• increase in temperature - reaching the melting point

  heat
• lowering the pressure - decompression melting

  pressure
• addition of volatiles - lowers the melting temperature

  volatiles
• decompression melting of upwelling mantle

  mid-oceanic ridges
• subducting slabs contains volatiles lowering melting temperature

  subduction zones
• high temperature in mantle plumes induces melting

  hot spots
• any process that causes the magmatic composition to change

  magmatic differentiation
• process by which different minerals crystallize at distinct temperatures as a magma cools; the sequence is : olivine, pyroxene, amphibole, and biotite

  fractional differentiation
• occurs when only a portion of a rock melts within the earth's crust or mantle, it results in the formation of a magma with a distinct composition

  partial melting
• involves the incorporation of surrounding rock into a magma chamber, the assimilated material interacts with the magma altering its composition

  country rock assimilation
• occurs when two or more magmas with different compositions blend together, this process leads to formation of hybrid magma


  magma mixing
• formed from solidification of molten material called magma (intrusive) or lava which flows out from the depths (extrusive)


  igneous rocks
• as magma cools, certain minerals crystallize first at relatively high temperature, in successively lower temperature, other minerals begins to crystallize

  bowen's reaction series
• describes the crystallization of specific minerals as temperature decreases

  discontinuous series
• sequence of mineral that form a temperature in a more gradual manner; doesn't involve discrete phases

  continuous series
• igneous rocks formed at the depth, peridotite, gabbro, diorite, granite

  intrusives (plutonic)
• molten rock solidified at the surface, komatiite (rare), basalt, andesite, rhyolite

  extrusives (volcanic)
• magma : gabbro - lava ; basalt
• massive intrusion more than 100 sq. km in outcrop area

  batholith