论文部分内容阅读
The Jiujiang-Ruichang area in northwestern Jiangxi extends along the western part of theminerogenic belt of the middle-lower Yangtze Valley in a terrain of sediments ranging fromOrdovician to Triassic in age with NEE-folds,and NW-compressive,NNW-tensile andNEE-compressive-shearing faults as the major structures.Igneous rocks are mostly intermediate-acidepizonal intrusive bodies.Typical copper mineralizations in this area include the skarn-type and stratiform Cu-bearingpyrite-type deposits at Wushan and the porphyry and breccia-pipe type copper-molybdenum depositsat Chengmenshan.Silurian strata,with a great thickness and an average copper content of 51 ppm,are consideredto be the source bed of copper mineralization,as is evidenced,among other things,by the presenceof an envelope which is notably impoverished in Cu around most of the deposits.Magmatic rockswhich intruded into the Silurian strata often have relatively high alkali contents and K_2O/Na_2Oratios,with extensive potash alteration.Magmatic rocks in the area are of co-melting type or mixed type.The magma assimilated alarge quantity of country rocks while ascending.They are characterized by high REE contents,ab-sence of Eu anomalies and high LREE/HREE ratios.Ancient head and strontium isotopes were de-tected in feldspar megaphenocrysts from the granodiorite porphyry.Hydrothermal convective circulation systems of magmatic water and supergenic water wasextensively developed in the magmatic and country rocks,in which copper,potassium and otherore-forming components were extracted from the country rocks and concentrated through heating,boiling and evaporating.When the ore-forming fluids found their way into the skarn zone or theunconformity between the Wutong Formation and the Huanglong Formation,ore precipitation wouldhave occurred as a result of changing media.If the concentration of KCl exceeded 9%,copper andother ore-forming components might have been deposited in magmatic rocks,forming theporphyry-type ore deposits.
The Jiujiang-Ruichang area in northwestern Jiangxi extends along the western part of theseinerogenic belt of the middle-lower Yangtze Valley in a terrain of sediments ranging from Ordovician to Triassic in age with NEE-folds, and NW-compressive, NNW-tensile andNEE-compressive -shearing faults as the major structures. Igneous rocks are mostly intermediate-acidepizonal intrusive bodies. Typical copper mineralizations in this area include the skarn-type and stratiform Cu-bearing pyrite-type deposits at Wushan and the porphyry and breccia-pipe type copper-molybdenum depositsat Chengmenshan. Silurian strata, with a great thickness and an average copper content of 51 ppm, are considered to be the source bed of copper mineralization, as is evidenced, among other things, by the presence of an envelope which is not likely impoverished in Cu around most of the deposits. Magmatic rockswhich intruded into the Silurian strata often have relatively high alkali contents and K_2O / Na_2Oratios, with extensive potash alterat ion. Magmatic rocks in the area are of co-melting type or mixed type. The magma assimilated a large quantity of country rocks while ascending. They are characterized by high REE contents, ab-sence of Eu anomalies and high LREE / HREE ratios. Ancient head and strontium isotopes were de-tected in feldspar megaphenocrysts from the granodiorite porphyry. Hydrothermal convective circulation of magmatic water and supergenic water wasexly developed in the magmatic and country rocks, in which copper, potassium and other core-forming components were extracted from the country rocks and concentrated through heating, boiling and evaporating .When the ore-forming fluids found their way into the skarn zone or theunconformity between the Wutong Formation and the Huanglong Formation, ore precipitation wouldhave occurred as a result of changing media.If the concentration of KCl exceeded 9%, copper andother ore-forming components might have been deposited in magmatic rocks, forming theporphyry-type ore deposits.