| The diabases and basalts are the products of mafic magma in different depth resulting from the Emei mantle plume,and show as homogeneity and heterogenous phase.Studies on Emeishan basalt mainly focused on the distribution,the genesis of related deposits,the eruption time,the petrogeochemistry in the past,while there was just little research on the metallogenic theory of diabase.The diabases in Luodian-Wangmo are the products of the late stage of Emeishan Large Igneous Province(ELIP).The eruption time limit of ELIP is still controversial due to the poor research and lack of high-precision zircon U-Pb chronological data.Moreover,the granodiorite vein discovered in the study area invaded the diabase is still in poor research.Many mineral deposits are spatially related to the diabases,therefore,in this paper,the elemental geochemical characteristics,zircon U-Pb dating,quartz Rb-Sr dating,Sr-Nd-Pb isotope,Hf isotope,fluid inclusion temperature and composition,and geological features of mineral deposits have been carefully researched in order to shed light on the matallogenic relation between Luodian jade,Cu,Zn,Pb deposits and the diabases and the hypabyssal magmatism and its metallogenetic effects,the conclusions are shown as follows:1.The magma resources of diabase and granodiorite have been clarified: The Sr-Nd-Pb isotope of diabase suggested that it probably has been caused by 10%-12% partial melting of the garnet peridotite in their source region that interacted with the upwelling Emei plume at the periphery of the plume.The zircons Lu-Hf isotope showed that the Luodian granodiorite has been resulted from the partial melting of relatively enriched mantle source region with crustal contamination.2.The reliable age of diabase has been obtained: The 261.2±2.6 Ma age of zircon SHRIMP U-Pb may imply the eruption time of magmatic event at the periphery of the plume is probably same with the eruption center of ELIP,and the ELIP formed by a mantle plume at ~260 Ma.3.The age of granodiorite has been determined: The 164.3±2.4 Ma age of LA-ICP-MS zircon U-Pb and the zircon Lu-Hf isotope may show that the mantle magma had invaded into the shallow in the Intracontinental extension stage in the Jurassic.4.The metallogenic possible relationship between diabase and Luodian jade: The magmatic hydrothermal from the invasion of diabase had supplied the necessary energy and temperature for the formation of Luodian jade.In this stage,the limestone had supplied plenty Ca and few Mg,while the Si,Al,Mg,K,Na had been from the magmatic hydrothermal,then because of the decompression boiling and the escape of a large amount of volatiles,the interchange of material between magmatic hydrothermal and wall rock had lead to the formation of jade as a result of the broken inner balance of magmatic hydrothermal.Fluid inclusion of tremolites in Luodian jade show that there had been two stages of hydrothermal activities at least,138? from Guangu and Echunm and 215? from Luomu.Fluid inclusion composition may show that the escape of a large amount of volatiles during the rise of ore-forming fluid.5.The mineralization of the Jiaoxiang gold deposit: The Wangmo Jiaoxiang gold deposit has the metallogenic similar geological background and mineralization with Carlin-type gold deposits in Southwest Guizhou.The ores REE show that they probably came from the same mantle source,the diabase taking Au had invades into the shallow crust along deep fractures and the deep infiltration cycle of underground water on the diabase and wall rock had extracted the Au,Cu,Pb,Zn and lead the formation of ore-forming hydrothermal.The gold deposit formation is because of the change of materialized conditions,the hybrid of meteoric water,the interaction between ore-forming fluid and wall rock,the sulfurization effect active Fe(came from bacterial reduction under open sedimentation conditions)in tuff(pyritization and sanding)in the faults formed in the Yanshanian.6.The metallogenic epoch and mineralization of the Jiaoxiang copper-lead-zinc deposit: The deposits had been formed in the late Cretaceous.Sr isotopes indicated that the ore-forming fluid has the features of both mantle and crust.After the hypabyssal magmatism in late Permian,the deep infiltration cycle of underground water had extracted the Au,Cu,Pb,Zn in both diabase and wall rock,and leads the formation of ore-forming hydrothermal in underground water.The Jiaoxiang copper-lead-zinc deposit is formed because of the large change of the ore-forming environment,such as the resurrection of deep fractures through the lithosphere(great contributions to regional mineralization)in the middle and late stage of Yanshanian,the faults formation in the late stage of Yanshanian,the hybrid of meteoric water and ore-forming hydrothermal.7.The matallogenic model has been built and the metallogenic effect of hypabyssal magmatism has been summarized: The tectonic location of the study area is located at the triple junction of the Eurasian plate,Indian plate and the Pacific plate.The metallogenic elements had enriched in the sediments and igneous rocks during the development and evolution in the area,moreover,the multi-stage magmatic activities had provided the metallogenic material,the power source and the mineralization tectonic pattern.The deposits in the area are the products of multi-stage magmatic activities,and the intrusion of diabase had played a major role in the mineralization of luodian jade.The deep infiltration cycle of underground water had extracted the ore-forming material of both diabase and wall rock,and leads the formation of ore-forming hydrothermal in underground water.The tectonic movement and ore-forming hydrothermal had resulted in activation and transfer of ore-forming elements and the formation of gold and copper-lead-zinc deposit.In this paper,metallogenic effect of hypabyssal magmatism is concluded according to the source transport and metallogenic kinetic energy resulting from Emei mantle plume,ore-forming material supporting from hypabyssal magmatism,metallogenic series and metallogenic epoch decided by hypabyssal magmatism,mineralization mechanism resulting from hypabyssal magmatism,matallogenic model set by hypabyssal magmatism: the mafic magmatic hypabyssal magmatism had supplied ore-forming material for related deposits and the mafic magmatic and intermediate-acid hypabyssal magmatism had supplied metallogenic energy.Related deposits had been formed in the Hercynian and middle and late Yanshanian.The guangu,Echun,Luomu jade deposits,the Jiaoxiang gold deposit and copper-lead-zinc deposit had been formed due to the hypabyssal magmatism resulting from Emei mantle plume,and these deposits made up the metallogenic series in this area. |
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