Origin Of Hamaling Copper-Gold Deposit In Tongling Region And Its Significance For Deep Prospecting

The Tongling ore concentrated area is an important copper-gold polymetallic ore concentration area in the middle and lower Yangtze River metallogenic belt in eastern China.Its metallogenic processes are closely related to the Yanshanian intrusive rocks.On the basis of systematically summarizing previous research data and achievements,this paper studied the genesis of the Hamaling copper-gold deposit in the Lower Paleozoic strata located in the southern part of the ore concentrated area,and discussed the characteristics of its ore-controlling elements and metallogenesis.The model is compared with regional mineralization and useful discussion of the regional metallogenic model has been conducted.There are four types of mineralization in the Hamaling copper-gold deposit: hydrothermal vein mineralization,breccia mineralization,alteration rock mineralization,and contact exchange skarn mineralization.The ore-forming process is divided into two stages and seven stages.Both stages of mineralization are closely related to deep hydrothermal activity.The Re-Os isotope isochron age of molybdenite in early mineralization is 141.1 ± 1.7 Ma.The Pb isotope composition of ores indicates that the source of ore-forming material is mainly related to magmatic rocks.The results of rock geochemical analysis indicate that the Hamaling quartz diorite is mainly characterized by medium,magnesium-depleted,alkali-rich,quasi-aluminum,and high-potassium-calcium-alkaline series.The zircon U-Pb isotope age(LA-ICP-MS)of the rock mass is 135.94±0.79 Ma.The magma originated from lithospheric mantle,lower crust and upper crust.In the process of remelting and magmatic evolution of the magma source area,roughly three magmatic chambers are formed: the upper mantle magma chamber,the deep magma chamber in the lower crust,and the shallow magma chamber in the upper crust.In the process of magma evolution,obvious magma mixing and crystallization differentiation occurred;the bottom-intrusive mantle-derived magma and the lower crust partially melted magma were chemically mixed,and the magma in the deep magma chamber magma and the magma in the shallow magma chamber were physically mixed.The crystallization differentiation mainly occurs in the bottom-intrusion mantle source magma and deep magma chamber.The separation and crystallization of mafic minerals and apatite and other minerals make the deep magma evolve from basic to neutral.The intrusive rocks associated with mineralization in the Tongling area formed in the late Jurassic-Early Early Cretaceous period.At this time,the tectonic setting in eastern China was in the continental marginal arc-orogenic belt,and the intrusive rocks associated with Arc magmatism formed in the Tongling area.Through comprehensive analysis of ore-controlling elements,a metallogenic model of the Hamaling copper-gold deposit was established,and it was demonstrated that it possesses similar stratigraphic,structural,and magmatic rock conditions as regional typical deposits.This indicates that the existing regional metallogenic model is also applicable to the Lower Paleozoic strata,and that the Lower Paleozoic strata in the copper region have good prospecting potential.Based on the established metallogenic model,some suggestions were put forward for the ore prospecting prediction in the mining area.And a useful discussion was also given on the prospecting work in the ore-gathering area,emphasizing the effect of regional antiform anticlines in rock-guiding and deeply-cutting fault in ore-conduction.The ore-forming action of the large fault structure proposed the "two-stage rock-guiding ore-conduction" model.