Isotopic Geochemical Characteristics Of Lianhuaxin Copper (Molybdenum) Polymetallic Deposit, Jiangxi Province

Lianhuaxin Copper-molybdenum polymetallic deposit is located in the northern part of Jiangxi Province. West of Jiangnan uplift fold belt, south west of Jiuling metallogenic belt. Few people have studied this deposit. There are some researches about geological features, major element, trace elements, fluid inclusions, Pb-S stable isotopes, metallogenic chronology and so on. This text based on the combined results of these researches. Studying its characteristics about isotopic dating of diagenetic and Sr-Nd-Pb-O-S isotope geochemistry, investigating the ore granite genesis, material sources, diagenetic times and tectonic setting, and the metallogenic epoch, the material sources and geological background about the ore-forming. And the relationship between diagenesis and mineralization. Mainly achieved the following understanding:1.Using LA-ICP-MS to the single grain zircon in situ micro area U-Pb isotope dating, getting that the weighted average age of 206Pb/238 U is 833±13Ma. It is belonging the granites in neoproterozoic Jinningian. The zircon crystal structure and characteristics of rare earth elements all show that it belongs typical crust source magma genesis zircon. Test age represents the magma crystallization age.Mineralization age is 158.1±3.1Ma.It shows that the deposit formed in the late Jurassic Epoch Yanshan interim, it obviously different from ore-bearing rocks’ diagenetic age. The mineralization should be the product of south China Mesozoic second large-scale mineralization. It is nearly concerns Yanshanian granite.2. The Sr、Nd、Pb、O isotope characteristics and Sr-Nd、Sr-O isotopic tagged all show that the ore-bearing rock(Biotite granite) belongs to I-S transition-type granites or crust-mantle mixed granite, formed when the Yangtze and Cathaysian plateoceanic have taken place crust subducted and arc-continent collision along China Nanyang. It is a product of mixing with the molten magma in volcanic arc crust when mantle-derived magma rises.3.The characteristics of the ores’ S、Pb isotopes show that crust-mantle mixing, with magma source, that shows the ore-forming material came from the magmatic hydrothermal which is deep crust-mantle mixing. Ore and wall rock have different Pb isotopic characteristics, it shows the processes of the origin don’t come from wall rock. Combining ore-forming isotope chronology, it shows that the deposit was formed when multi-stage lithospheric stretched after the Pacific plate subduction.4.Isotope chronology of diagenetic metallogenia show that Lotus core deposit has the characteristics of the porphyry copper deposits. It belongs the porphyry- epithermal gold- copper mineralization system which relate with calcium alkaline volcanic intrusive granitic magmatism. There is a speculation that buried Yanshanian granite existed under the Jinningian granite.Combined with the above research and predecessors’ studying results, perfect the metallogenic model and propose new prospecting ideas.