Geochemical Characteristics And Petrogenesis Of Igneous Rocks In Dachang Tin-polymetallic Orefield,Guangxi

The Dachang tin polymetallic ore field in Guangxi is an important non-ferrous mining base in China and a well-known superlarge ore deposit at home and abroad.Many people have conducted extensive research on it,but the interrelationships between rock formations and mineralization,especially mineralization The relationship between the mantle source components in the material and the rock mass is not very clear.On the basis of previous work,this paper systematically conducted major probes of trace elements,rare earth elements,Sr-Nd isotopes,and mica and plagioclase minerals of intrusive rocks in Dachang orefield.Rock Formation and Its Relationship with Mineralization.The study shows that:The lithologic SiO2 content in the Longpangong compound granite rock mass is obviously negatively correlated with TiO2?Al2O3?CaO?Fe2O3?MgO the trace elements and the Rb/Sr,Nb/Ta?and the rare earth element characteristics Shows that they have cognate magma evolution characteristics.The trace elements,ratios of Rb/Sr?Nb/Ta?and rare earth elements all show that they have homologous magmatic evolution characteristics.The rocks are characterized by high silicon,alkali-rich,potassium-rich,low-titanium,and low-calcium,K2O>Na2O,A/CNK=0.96 to 1.58,and generally>1.1;rare earth elements show significant enrichment of light rare earth elements,and they are strongly depleted.(?Eu = 0.16 to 0.45),showing a "V" type rightward tilt characteristic on the rare earth partition pattern map.These features are similar to the "S-type" granites of the South China Rock and show the characteristics of crust source;from Longxianggai granite to granite porphyry veins to quartz diorite dykes(including diorite clastic rocks),?Nd(t)gradually increased(-7.9?-9.6?6.9?-8.7?-4.6?-6.2),T2DM gradually decreased(1.5?1.6GMa?1.45?1.6Ga?1.27?1.4Ga),indicating Dachang magmatic activity The main body comes from the remelting of the crustal material of the Middle Proterozoic,but during the magmatic activity,The intensity of material participation in mantle gradually increased;through geochemical characteristics,characteristic ratios such as TFeO/MgO and Ga/Al(104),and comparison with the rock masses of Qitianling and Jinjiling in Nanling area,it was considered that the Longmenga compound granite The body has the characteristics of A-type granite and is formed in the regional tectonic setting environment.The Longtanga compound granite body has a close temporal and spatial relationship with the Dachang tin polymetallic ore,and the rock body provides the heat source and partial ore-forming material for mineralization.The mantle source components mixed in the ore formation may not be provided by the Longxianggai granite,but may be the source of the mantle source rising along deep faults.The ascending channel may be consistent with the channel that the rock vein embeds.