deposited-metal zone
21India — /in dee euh/, n. 1. Hindi, Bharat. a republic in S Asia: a union comprising 25 states and 7 union territories; formerly a British colony; gained independence Aug. 15, 1947; became a republic within the Commonwealth of Nations Jan. 26, 1950.… …
22Sedimentary exhalative deposits — (abbreviated as SEDEX from SEDimentary EXhalative) are ore deposits which are interpreted to have been formed by release of ore bearing hydrothermal fluids into a water reservoir (usually the ocean), resulting in the precipitation of stratiform… …
23Ore genesis — The various theories of ore genesis explain how the various types of mineral deposits form within the Earth s crust. Ore genesis theories are very dependent on the mineral or commodity. Ore genesis theories generally involve three components:… …
24Marcellus Formation — Stratigraphic range: Middle Devonian …
25nuclear reactor — Physics. reactor (def. 4). Also called nuclear pile. [1940 45] * * * Device that can initiate and control a self sustaining series of nuclear fission reactions. Neutrons released in one fission reaction may strike other heavy nuclei, causing them …
26poison — poisoner, n. poisonless, adj. poisonlessness, n. /poy zeuhn/, n. 1. a substance with an inherent property that tends to destroy life or impair health. 2. something harmful or pernicious, as to happiness or well being: the poison of slander. 3.… …
27optics — /op tiks/, n. (used with a sing. v.) the branch of physical science that deals with the properties and phenomena of both visible and invisible light and with vision. [1605 15; < ML optica < Gk optiká, n. use of neut. pl. of OPTIKÓS; see OPTIC,… …
28South America — South American. a continent in the S part of the Western Hemisphere. 271,000,000; ab. 6,900,000 sq. mi. (17,871,000 sq. km). * * * Continent, Western Hemisphere. The world s fourth largest continent, it is bounded by the Caribbean Sea to the… …
29pre-Columbian civilizations — Introduction the aboriginal American Indian (Mesoamerican Indian) cultures that evolved in Meso America (part of Mexico and Central America) and the Andean region (western South America) prior to Spanish exploration and conquest in the 16th …
30dating — I In geology and archaeology, the process of determining an object s or event s place within a chronological scheme. Scientists may use either relative dating, in which items are sequenced on the basis of stratigraphic clues (see stratigraphy) or …
