GEOL 1301 Fall 2014 Lecture 9Outline of Last Lecture I. Rock forming mineralsII. Three families of Rocksa. Igneousb. Sedimentaryc. MetamorphicOutline of Current LectureI. Properties of Rocksa. Sizesb. Shapesc. Crystals or grainsII. Rock CyclesIII. Mineral deposits Current LectureWhat determines the properties of rocks? Mineralogy (the kinds and proportions of minerals that make up a rock) and texture (the sizes, shapes, and spatial arrangement of its crystals or grains) define a rock. The mineralogy and texture of a rock are determined by the geologic processes by which it formed.What are the three families of rocks and how do they form? Igneous rocks form by the crystallization of magmas as they cool. Intrusive igneous rocks cool slowly in Earth’s interior and have large crystals. Extrusive igneous rocks, which cool rapidly at Earth’s surface, have a glassy or fine-grained texture. Sedimentary rocks form by the lithification of sediments after burial. Sediments are derived from the weathering and erosion of rocks at Earth’s surface. Metamorphic rocks form when igneous, sedimentary, or other metamorphic rocks are subjected to high temperatures and pressures in Earth’s interior that change their mineralogy, texture, or chemical composition.How does the rock cycle explain the transformation of rocks from one type into another? The rock cycle relates geologic processes driven by the plate tectonic system and the climate system to the formation of the three families of rocks. We can view these processes by starting at any point in the cycle, such as the creation of new oceanic lithosphere at a spreading center as two continents These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.drift apart. The ocean basin gets wider until at some point the process reverses itself. As the basin closes and igneous rocks and sediments are subducted beneath a continent, they begin to melt to form a new generation of igneous rocks. The heat and pressure associated with subduction and withthe intrusion of these igneous rocks transforms surrounding rocks into metamorphic rocks. Ultimately, the two continents collide, and these igneous and metamorphic rocks are uplifted into a high mountain chain. The uplifted rocks slowly weather, and their fragments are deposited as sediments.How do deposits of economically valuable minerals form? Ores are deposits of minerals from which valuable metals can be recovered profitably. Hydrothermal deposits of ore minerals are formed when groundwater or seawater reacts with a magmatic intrusion to form a hydrothermal solution. The heated water transports soluble minerals to cooler rocks, where they are precipitated infractures. The resulting ores may be found in veins or in disseminated deposits. Igneous ore deposits typically form when minerals crystallize from cooling magma, settle, and accumulate at the base of the magma body. They are often found as layered accumulations of minerals. Other ore minerals are chemically precipitated in sedimentary environments to which metals are transported in