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Saprolite is a chemically weathered rock. Saprolites form in the lower zones of soil profiles and represent deep weathering of the bedrock surface. In most outcrops its color comes from ferric compounds. Deeply weathered profiles are widespread on the continental landmasses between latitudes 35°N and 35°S. Conditions for the formation of deeply weathered regolith include a topographically moderate relief flat enough to prevent erosion and to allow leaching of the products of chemical weathering. A second condition is long periods of tectonic stability; tectonic activity and climate change can cause erosion. The third condition is humid tropical to temperate climate. Poorly weathered saprolite grit aquifers are capable of producing groundwater, often suitable for livestock. Deep weathering causes the formation of many secondary and supergene ores – bauxite, iron ores, saprolitic gold, supergene copper, uranium and heavy minerals in residual accumulations.〔 ==Definition, description and locations== Saprolite (from Greek σαπρος = putrid + λιθος = rock) is a chemically weathered rock (literally, it means "rotten rock"). More intense weathering results in a continuous transition from saprolite to laterite. Saprolites form in the lower zones of soil horizons〔 and represent deep weathering of the bedrock surface. In lateritic regoliths – regoliths are the loose layer of rocks that rest on the bedrock – saprolite may be overlain by upper horizons of residual laterite; most of the original profile is preserved by residual soils or transported overburden.〔 Weathering formed thin kaolinitic () saprolites 1,000 to 500 million years ago; thick kaolinitic saprolites 200 to 66 million years ago; and medium-thick immature saprolites 5 million years ago.〔 The general structure of kaolinite has silicate () sheets bonded to aluminium hydroxide () layers. Iron compounds are the primary coloring agents in saprolites. At most outcrops the color comes from ferric compounds; the color relates to the mineralogy and particle size.〔 Submicron-sized goethite () is yellow; coarse goethite is brown.〔 Submicron-sized hematite () is red; coarse hematite is gray to black.〔 Regoliths vary from a few meters to over thick, depending on the age of the land surface, tectonic activity, climate, climate history and the composition of the bedrock.〔 Although these deeply weathered terrains now occur in a wide variety of climates ranging from warm humid to arid, tropical to temperate, they were formed under similar conditions in the past.〔 In parts of Africa, India, South America, Australia and southeast Asia, regolith has been forming continuously for over 100 million years. Deeply weathered regoliths are widespread in the inter-tropical belt, particularly on the continental landmasses between latitudes 35°N and 35°S.〔 Similar weathered regoliths exist at much higher latitudes – 35–42°S in southeast Australia (Victoria and Tasmania), 40–45°N in the United States (Oregon and Wisconsin) and 55°N in Europe (Northern Ireland, Germany) – although these are not regionally extensive.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「saprolite」の詳細全文を読む スポンサード リンク
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