Abstract
The Haisugou porphyry Mo deposit is located in the northern Xilamulun district, northeastern China. Based on alteration and mineralization styles and crosscutting relationships, the hydrothermal evolution in Haisugou can be divided into three stages: an early potassic alteration stage with no significant metal deposition, a synmineralization sericite-chlorite alteration stage with extensive Mo precipitation, and a postmineralization stage characterized by barren quartz and minor calcite and fluorite. The coexistence of high-salinity brine inclusions with low-salinity inclusions both in potassic alteration stage (~440°C) and locally in the early time of mineralization stage (380–320°C) indicates the occurrence of fluid boiling. The positive correlations between the homogenization temperatures and the salinities of the fluids and the low oxygen isotopic compositions (δ18Ofluid < 3‰) of the syn- to postmineralization quartz together suggest the mixing of magmatic fluids with meteoric water, which dominated the whole mineralization process. The early boiling fluids were not responsible for ore precipitation, whereas the mixing with meteoric water, which resulted in temperature decrease and dilution that significantly reduced the metal solubility, should have played the major role in Mo mineralization. Combined fluid inclusion microthermometry and chlorite geothermometer results reveal that ore deposition mainly occurred between 350 and 290°C in Haisugou.
Highlights
The global molybdenum resource comes almost completely from porphyry-type deposits. In some of these deposits Mo is recovered as byproduct (i.e., porphyry Cu-Mo (±Au) deposits), whereas, in others, the deposits are characterized by high abundances of Mo but virtually no Cu or Au such as the Climax-type deposits along the North American Cordillera [1,2,3]
Unlike the Climax-type Mo deposits, which typically develop in backarc or intracontinental rifts and are associated with alkaline magmas [1], the porphyry Mo deposits in the Chinese Qinling-Dabie orogenic belt are related to high-K calcalkaline to shoshonitic magmas generated in syn- to postcollisional tectonic settings and have been suggested to belong to a new class of Dabie-type porphyry Mo deposits [7, 10,11,12]
The present study aims at tracing the genesis and the hydrothermal evolution leading to alteration, metal concentration, and formation of the Haisugou porphyry Mo deposit through detailed study of fluid inclusion microthermometry, oxygen isotope, and chlorite chemistry
Summary
The global molybdenum resource comes almost completely from porphyry-type deposits. In some of these deposits Mo is recovered as byproduct (i.e., porphyry Cu-Mo (±Au) deposits), whereas, in others, the deposits are characterized by high abundances of Mo but virtually no Cu or Au (i.e., purely porphyry Mo deposits) such as the Climax-type deposits along the North American Cordillera [1,2,3]. Most of China’s Mo deposits are located in the Qinling-Dabie orogenic belt in Central China (>8.5 Mt Mo metal [4, 6, 7]). The eastern section of the Central Asian orogenic belt in northeastern China (>11 Mt Mo metal [8, 9]). Northeastern China has become the largest Mo ore region in China with the continuous discoveries of many porphyry
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