Minerals and Rocks PDF

Minerals and Rocks! 1 Review: Classification of Rocks In broadest sense, rocks can be classified as: IGNEOUS SEDIMENTARY METAMORPHIC METAMORPHIC ROCKS: IGNEOUS or SEDIMENTARY ROCKS that have been transformed by high pressure, high heat, and/or contact with hot magma. Find su...

Minerals and Rocks! 1 Review: Classification of Rocks In broadest sense, rocks can be classified as: IGNEOUS SEDIMENTARY METAMORPHIC METAMORPHIC ROCKS: IGNEOUS or SEDIMENTARY ROCKS that have been transformed by high pressure, high heat, and/or contact with hot magma. Find such conditions: deep in the Earth where tectonic plates meet NOTE: Transformation/METAMORPHISM process does NOT melt rocks, it just turns them into DENSER (remember density is Examples of METAMORPHIC rocks. mass/volume) more compact rocks. 2 Metamorphic Rocks METAMORPHIC ROCKS: rocks formed when HEAT, PRESSURE and/or CHEMICAL CHANGES alter original/parent rocks, generating completely new rocks. NOTE: parent rocks do NOT melt, otherwise an IGNEOUS rock would be formed. Parent rock can be SEDIMENTARY, IGNEOUS or even at times another METAMORPHIC ROCK. METAMORPHIC from Greek, meaning “to change form” 3 AGENTS of METAMORPHISM: INCREASED TEMPERATURE Here we see METAMORPHIC ROCK that is INCREASED PRESSURE estimated to be up to 3.8 billion years old CHEMICAL CHANGES (Greenland)!!! Let’s consider how the 3 AGENTS of METAMORPHISM come about! 3 Metamorphic Rocks: Temperature Consider 3 AGENTS of METAMORPHISM: INCREASED TEMPERATURE: encountered when sediment/rock layers find themselves buried deeper and deeper in the ground due to added sediment/rock layers above them. as descend into Earth, TEMPERATURES INCREASE at approximately 25oC per kilometer deeper our rock layer of interest descends, the hotter temperatures become, allowing for METAMORPHISM. Mining for MARBLE (a METAMORPHIC ROCK) in Greece. NOTE: weight of sediment/rock layers piling on to layer of interest also causes INCREASE in PRESSURE. 4 Metamorphic Rocks: Temperature Consider 3 AGENTS of METAMORPHISM: Also encounter INCREASED TEMPERATURE at SUBDUCTION ZONES (where one TECTONIC PLATE descends below the other) At SUBDUCTION ZONES: intense FRICTION between TECTONIC PLATES results in HEAT/INCREASED TEMPERATURES some of rock on DESCENDING PLATE will MELT, ultimately forming IGNEOUS ROCK YELLOW REGION in sketch above demonstrates where METAMORPHIC rock adjacent to/next to this hot ROCK would form at a SUBDUCTION MOLTEN/MELTED rock or MAGMA will heat up, ZONE, adjacent to/next to but NOT melt, thus forming METAMORPHIC MOLTEN/MELTED ROCK or MAGMA. ROCK. NOTE: here too, there is also INTENSE PRESSURE 5 Metamorphic Rocks: Pressure Consider 3 AGENTS of METAMORPHISM: INCREASED PRESSURE PRESSURE can INCREASE due to: CONVERGENT PLATE huge weight of sediment/rock layers forming BOUNDARY above our rock layer of interest collision of TECTONIC PLATES (at CONVERGENT PLATE BOUNDARIES). As add layers of high FRICTION caused by sliding of sediment/rock above rock layer of interest, TECTONIC PLATES past one another (at PRESSURE TRANSFORM PLATE BOUNDARIES). INCREASES! TRANSFORM PLATE BOUNDARY 6 Metamorphic Rocks: Chemical Reactions Consider 3 AGENTS of METAMORPHISM: CHEMICAL CHANGES CHEMICAL CHANGES can occur when: hot fluids and vapors/gases present at HIGH TEMPERATURE and HIGH PRESSURE sites fill PORES of existing rocks. fluids/vapors/gases can trigger CHEMICAL REACTIONS or leave behind MINERALS that ultimately change CHEMICAL A CHEMICAL REACTION converting 2 minerals COMPOSITION/make up of PARENT/pre- (QUARTZ and CALCITE) into a new SILICATE existing rock. mineral, WOLLASTONITE (CaSiO3). 7 Metamorphic Rocks: Fun Facts METAMORPHISM (formation of METAMORPHIC ROCK) can occur almost instantaneously at TECTONIC PLATE BOUNDARIES or take millions of years deep below Earth’s surface. METAMORPHIC ROCKS: typically harder than SEDIMENTARY PARENT rocks MARBLE (left) is slightly harder than its SEDIMENTARY PARENT LIMESTONE (right). as hard or harder than IGNEOUS PARENT rocks form roots of mountain chains, becoming exposed to Earth’s surface when softer layers of rock above them WEATHERED/ERODED away. 8 Metamorphic Rocks: Examples SEDIMENTARY PARENT rock SHALE (MUDSTONE) becomes METAMORPHIC ROCK SLATE. As layers of SHALE become buried deeper and deeper in ground (due to increased number of sediment/rock layers above), TEMPERATURE and PRESSURE SEDIMENTARY PARENT rock SHALE (left) becomes INCREASE. METAMORPHIC ROCK SLATE (right). Thus, SLATE is formed. NOTE: SLATE can split into perfectly thin sheets (i.e., it has PERFECT CLEAVAGE). Thus, used as a building material (e.g., for roofing). A beautiful SLATE roof. 9 Metamorphic Rocks: Examples SCHIST is a METAMORPHIC rock that can form from the transformation of various SILICATE minerals, including MICA, HORNBLENDES and TALC! GNEISS: SCHIST (all examples above) can form from METAMORPHIC rock with distinct “banding”/layers. transformation of various SILICATE minerals different layers observed in “banding” correspond to different MINERALS. like GRANITE (its PARENT IGNEOUS rock), it consists primarily of FELDSPARS, MICA and QUARTZ (MINERALS). GNEISS, with its distinctive can also come from PARENT IGNEOUS rock RHYOLITE, banding, has GRANITE or the EXTRUSIVE equivalent of INTRUSIVE GRANITE! RHYOLITE as its PARENT rocks. 10 Metamorphic Rocks: Examples QUARTZITE is a METAMORPHIC rock formed from SANDSTONE that has come into contact with deeply buried MAGMA. MARBLE: QUARTZITE is a METAMORPHIC rock formed from SANDSTONE. comes from SEDIMENTARY PARENT rocks LIMESTONE (and DOLOSTONE). often white in colour, can come in many different colours (including black, red, gray, pink) due to impurities. slightly harder than PARENT SEDIMENTARY rocks used as a building and sculpting material. Michelangelo’s “David” is MARBLE! 11 Thank you for listening! Next Lecture: GEOLOGIC TIME SCALE!!! Don’t forget!!! Birds first appeared during the Jurassic Period! 12