Geological Characteristics of Copper Mineralization,Jiujiang—Ruichang Area,Jiangxi Province,China

The Jiujiang-Ruichang area in northwestern Jiangxi extends along the western part of the minerogenic belt of the middle-lower Yangtze Valley in a terrain of sediments ranging from Ordovician to Triassic in age with NEE-folda,and NW-compressive,NNW-tensile and NEE-compressive-shearing faults as the major structures .Igneous rocks are mostly intermediate-acid epizonal 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 deposits at 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 notably impoverished in Cu aroud most of the deposits.Magmatic rocks which intruded into the Silurian strata often have relatively high alkali contents and K2O/Na2O ratios ,with extensive potash alteration.Magmatic rocks in the area are of co-melting type or mixed type.The magma assimilated a large quanity of country rocks while ascending.They are characterized by high REE contents,absence of Eu anomalies and high LREE/HREE ratios.Ancient lead and strontium isotopes were detected in feldspar megaphenocrysts from the granodiorite porphyry.Hydrothermal convective circulation systems of magmatic water of magmatic water and supergenic water was extensively developed in the magmatic and country rocks,in which copper,potassium and other ore-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 the unconformity between the Wutong Formation and the Huanglong Formation,ore precipitation would have occurred as a result of changing media,If the concentration of KCl exceeded 9%,copper and other ore-forming components might have been deposited in magmatic rocks,forming the porphyry-type ore deposits.

Geological characteristics of copper mineralization,Jiujiang-Ruichang area,Jiangxi Province,China

The Jiujiang-Ruichang area in northwestern Jiangxi extends along the western part of the minerogenic 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 and NEE-compressive-shearing faults as the major structures. Igneous rocks are mostly intermediate-acid epizonal 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 deposits at 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 notably impoverished in Cu around most of the deposits. Magmatic rocks which intruded into the Silurian strata often have relatively high alkali contents and K₂O/Na₂O ratios, with extensive potash alteration. 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, absence of Eu anomalies and high LREE/HREE ratios. Ancient lead and strontium isotopes were detected in feldspar megaphenocrysts from the granodiorite porphyry. Hydrothermal convective circulation systems of magmatic water and supergenic water was extensively developed in the magmatic and country rocks, in which copper, potassium and other ore-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 the unconformity between the Wutong Formation and the Huanglong Formation, ore precipitation would have occurred as a result of changing media. If the concentration of KCl exceeded 9%, copper and other ore-forming components might have been deposited in magmatic rocks, forming the porphyry-type ore deposits.