L08_Sedimentary_Rocks_Chemical_Weathering

Chemical sedimentary rocks are formed by precipitaon

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Unformatted text preview: it is in equilibrium with atmospheric CO2 (reminder: pH scale: 1 = very acidic, 7 = neutral, 14 = very basic) Chemical Weathering Produces a host of ‘secondary minerals’ Weathering of K- feldspar to produce kaolinite clay: 2KAlSi3O8 + 2CO2 + 11H2O à༎ Al2Si2O5(OH)4 + 2K+ +2HCO3- + 4H4SiO4 K- Feldspar kaolinite Remember that the CO2 comes from the atmosphere. The three basic rock types: Igneous All rock material starts out as igneous rock, that is, rock that solidifies directly from the liquid phase (magma, lava). Extrusive igneous rocks form by cooling of magma that reaches the Earth’s surface (lava). Typically fine- grained (small crystals). Intrusive igneous rocks form by cooling of magma within the earth. Typically coarse- grained (large crystals). Sedimentary Clas<c sedimentary rocks are composed of weathered fragments (ground- up bits) of the other rock types (also including sedimentary), typically deposited by water. Chemical sedimentary rocks are formed by precipita<on of minerals out of water. Includes limestones, coral reefs, and salt deposits. Metamorphic Rocks that have been par<ally altered, via par<al mel<ng or chemical processes (or both). The original rock type can usually be inferred. Complete mel<ng renders the rock an ‘igneous rock’. Clas<c Sedimentary Rocks Chemical Sedimentary Rocks Clas<c sedimentary rocks are classified largely according to par<cle size Clas<c Sedimentary Rocks Chemical Sedimentary Rocks Chemical sedimentary r...
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