Geochemistry is broadly concerned with the applicat.... chemic rock

Inasmuch as the Earth is composed of the chemical elements, all geologic materials and most geologic processes can be regarded from a chemical point of view. Some of the major problems that broadly belong to geochemistry are as follows: the origin and abundance of the elements in the solar system, galaxy, and universe ( ); the abundance of elements in the major divisions of the Earth, including the core, mantle, crust, hydrosphere, and atmosphere; the behaviour of ions in the structure of crystals; the chemical reactions in cooling magmas and the origin and evolution of deeply buried intrusive igneous rocks; the chemistry of volcanic (extrusive) igneous rocks and of phenomena closely related to volcanic activity, including hot-spring activity, emanation of volcanic gases, and origin of ore deposits formed by hot waters derived during the late stages of cooling of igneous magmas; chemical reactions involved in weathering of rocks in which earlier formed minerals decay and new! minerals are created; the transportation of weathering products in solution by natural waters in the ground and in streams, lakes, and the sea; chemical changes that accompany compaction and cementation of unconsolidated sediments to form sedimentary rocks; and the progressive chemical and mineralogical changes that take place as rocks undergo metamorphism. , sodium chloride), whereas others are progressively removed to form certain sedimentary rocks, including limestone and dolomite, and, where conditions are conducive for the formation of deposits by means of evaporation, gypsum (hydrous calcium sulfate), rock salt (halite), and potash deposits may occur. Major problems of organic geochemistry include the question of the chemical environment on Earth in which life originated; the modification of the hydrosphere, and particularly the , through the effects of life; and the incorporation of organic materials in rocks, including carbonaceous material in sedimentary rocks. Th! e nature and chemical transformations of biological material p! resent in deposits of coal, petroleum, and natural gas lie within the scope of organic geochemistry. Organic chemical reactions influence many geochemical processes, as, for example, rock weathering and production of soil, the solution, precipitation, and secretion of such dissolved materials as calcium carbonate, and the alteration of sediments to form sedimentary rocks. These include the study of the chemical composition of meteorites, the relative abundance of elements in the Earth, Moon, and other planets, and the ages of meteorites and of rocks of the crust of the Earth and Moon as established by radiometric means. These deficiencies are in turn related to the concentrations of these elements in rocks and the manner in which they are chemically combined within soils and rocks. chemic rock