变质岩实习2-变质碳酸岩.pptVIP

Metamorphic calcarous rocks 原岩为石灰岩和白云岩 化学成分上富CaO或富MgO Calcareous rocks are predominantly carbonate rocks, usually limestone or dolostone Typically form in a stable continental shelf environment along a passive margin They may be pure carbonate, or they may contain variable amounts of other precipitates (such as chert or hematite) or detrital material (sand, clays, etc.) Become metamorphosed when the passive margin becomes part of an orogenic belt Metacarbonates are metamorphosed calcareous rocks in which the carbonate component is predominant Marbles are nearly pure carbonate Calc-silicate rocks: carbonate is subordinate and may be composed of Ca-Mg-Fe-Al silicate minerals, such as diopside, grossular, Ca-amphiboles, vesuvianite, epidote, wollastonite, etc. Skarn: calc-silicate rock formed by metasomatism between carbonates and silicate-rich rocks or fluids Contact between sedimentary layers Contact between carbonate country rocks and a hot, hydrous, silicate intrusion, such as a granite 泥质条带灰岩（未变质） 矽卡岩多金属硫化物矿床 常见变质矿物： Calcite (方解石)， [CaMg]CO3 Dolomite (白云石)，[CaMg]CO3 Talc (滑石), Mg3[Si4O10](OH)2 Tremolite (透闪石) Ca2(MgFe)5[Si8O22](OH, F) Diopside (透辉石), CaMgSi2O6 Wollastonite (硅灰石), Ca2Si2O6 Grossular (钙铝榴石), Ca3Al2Si3O12 Olivine (镁橄榄石), Mg2SiO4 Serpentine (蛇纹石), (Mg,Fe,Ni)3Si2O5(OH)4 Chemographics in the CaO-MgO-SiO2?-CO2?-H2O system, projected from CO2 and H2O. The green shaded areas represent the common composition range of limestones and dolostones. Due to the solvus between calcite and dolomite, both minerals can coexist in carbonate rocks. The dark red left half of the triangle is the area of interest for metacarbonates. Carbonated ultramafics occupy the right half of the triangle. Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall. composition range of limestones composition range of dolostones Figure 29-2. A portion of the Alta aureole in Little Cottonwood Canyon, SE of Salt Lake City, UT, where talc, tremolite, forsteri