ASS #3 Key Terms & Concepts PDF

ASS #3 Key Terms Carbonado—An aggregate of many randomly oriented interlocking tiny diamond crystals that is the toughest form of diamond. Carbonate—A class of chemical compounds that contain carbon and oxygen. CLIPPIR Diamonds—Cullinan-like, Large, Inclusion-Poor, Pure, Irregular,...

ASS #3 Key Terms Carbonado—An aggregate of many randomly oriented interlocking tiny diamond crystals that is the toughest form of diamond. Carbonate—A class of chemical compounds that contain carbon and oxygen. CLIPPIR Diamonds—Cullinan-like, Large, Inclusion-Poor, Pure, Irregular, and Resorbed diamond. Core—The earth’s innermost layer. Cratons—Large, ancient, stable parts of the earth’s landmasses. Crust—The surface and outermost layer of the earth. Crustal Diamond—Rare diamond that forms in the continental crust at or near the earth’s surface due to meteorite impact or tectonic plate collision. Eruption—A geological process that delivers material (sometimes diamonds) to the surface. Geothermal Gradient—The rate of temperature increase with depth in the earth. Igneous Rock—A type of rock formed from a molten state. Lithosphere—The layer that contains the crust and the uppermost part of the mantle. Magma—Any molten rock within the earth. Mantle—The layer between the earth's crust and its core. Mantle Keels—A large, downward-protruding portion of the lithosphere under a craton. Metamorphic Rock—A type of rock that has been altered by heat and pressure. Metasomatism—A process in which chemical changes in minerals and rocks result from the introduction of material from external sources, often fluids or melts. Mineral—A natural, inorganic substance with characteristic chemical composition and usually characteristic structure. Pipe—A deep vertical formation at the earth’s surface that results from a kimberlite or lamproite eruption. Plate Tectonics—The theory of the formation, structure, and movement of the earth’s landmasses. Rocks—A natural material composed of one or more kinds of minerals. Subduction—The process in which a continental plate and an oceanic plate collide, forcing the oceanic plate down into the mantle. Superdeep Diamonds—Diamonds that formed at 410 km or deeper beneath the earth’s surface. Transition Zone—The layer between the upper and lower mantles. Key Concepts Diamond and graphite are both composed of carbon. The earth’s basic structure consists of the crust, mantle, and core. The mantle can be divided into three broad layers: the upper mantle, lower mantle, and a transition zone in between. Mantle convection drives the movement of the earth’s plates. Subduction is an essential part of diamond formation. Most diamond deposits are found on cratons or in the areas surrounding them. Diamonds form mainly in two types of rocks: peridotite and eclogite. Diamond formation requires extreme pressures and temperatures, as well as a source of carbon. The conditions for diamond formation exist within mantle keels under cratons. The majority of mined diamonds are lithospheric and superdeep. Not all diamonds form in mantle keels; superdeep diamonds form much deeper within the mantle. Diamonds form in mantle keels when carbon is available and free to bond with other carbon atoms without oxygen. Inclusions can indicate where a diamond formed within the earth. CLIPPIR diamonds crystallized from metallic melts in the transition zone or the lower mantle. The most common cause of blue color in diamonds is boron. Boron in blue diamonds originates from oceanic plates. Carbonado is the toughest form of diamond. Diamonds were delivered to the surface between 2.5 billion and 20 million years ago. Kimberlite and lamproite are the two igneous rocks that transport diamonds to the surface. Diamond-bearing kimberlite is much more common than diamond-bearing lamproite. Kimberlite tends to occur in the center of cratons, while lamproite occurs at their edges. Kimberlite and lamproite form pipe deposits. Very few kimberlites or lamproites contain diamonds in economic quantities.