Figure 3.12 Igneous Rocks (Lab ) The RockSedimentary Cycle Rocks (Lab ) Metamorphic Rocks (Lab ) Areas of regional metamorphism Compressive Compressive Stress Stress Products of Regional Metamorphism Products of Contact Metamorphism Foliated texture forms Non-foliated texture forms during compression during static pressure Texture Minerals Other Diagnostic Metamorphic Protolith Features Rock Name Non-foliated calcite, dolomite cleavage faces of Marble Limestone calcite usually visible quartz quartz grains are Quartzite Quartz Sandstone intergrown Foliated clay looks like shale but Slate Shale breaks into layers muscovite, biotite very fine-grained, but Phyllite Shale has a sheen like satin muscovite, biotite, minerals are large Schist Shale may have garnet enough to see easily, muscovite and biotite grains are parallel to each other feldspar, biotite, has layers of different Gneiss Any protolith muscovite, quartz, minerals garnet amphibole layered black Amphibolite Basalt or Andesite amphibole grains Texture Minerals Other Diagnostic Metamorphic Protolith Features Rock Name Non-foliated calcite, dolomite cleavage faces of Marble Limestone calcite usually visible quartz quartz grains are Quartzite Quartz Sandstone intergrown Foliated clay looks like shale but Slate Shale breaks into layers muscovite, biotite very fine-grained, but Phyllite Shale has a sheen like satin muscovite, biotite, minerals are large Schist Shale may have garnet enough to see easily, muscovite and biotite grains are parallel to each other feldspar, biotite, has layers of different Gneiss Any protolith muscovite, quartz, minerals garnet amphibole layered black Amphibolite Basalt or Andesite amphibole grains Identification of Metamorphic Rocks 12 samples 7 are metamorphic 5 are igneous or sedimentary Protoliths and Geologic History For 2 of the metamorphic rocks: Match the metamorphic rock to its protolith (both from Part One) Write a short geologic history of the sample 1. Formation of the protolith 2. Burial to the depth where metamorphism takes place 3. Metamorphism 4. Uplift and erosion to bring the metamorphic rocks to the surface Metamorphic Metamorphic Rock Protolith Protolith Rock Name Geologic History Sample Name Sample Number Number 2 Gneiss 7 Granite 1. Granitic magma intruded in the Earth's crust and crystallized to form granite. 2. Granite was forced deeper in the crust by plate tectonics. 3. Granite was metamorphosed to form gneiss. 4. The rocks above the gneiss were eroded away to expose the gneiss at the surface. Interpretation of Metamorphic Rocks Contact Metamorphism Match the protolith to the metamorphic rock Determine the thermal gradient (direction of increasing temperature) during contact metamorphism Regional Metamorphism Using five metamorphic rocks (from Part One), determine the direction of the thermal gradient during regional metamorphism for this example Also, determine the direction of compressive stress during metamorphism .