The Characteristics Of The Petrology, Geochronology And The Metallogenetic Of Iron Ore Deposits In Tangquan-Gaoxing Of Southwestern Fujian Province

Tangquan-Gaoxing area in Southwest Fujian is located in Datian County, Fujian Province. The area is part of "Yongmei Depression Belt" in late Paleozoic, which is in the intersection of the northeast Zhenghe-Dabu deep fault zone and northwest Jinjiang-Yongan deep fault zone, and is an important iron ore belt in Southwestern Fujian. Tangquan and Gaoxing iron ore deposits belong to this metallogenic belt.This paper mainly discusses the genesis relationship between the rocks and iron ore deposits, through studing the characteristics of petrology and geochronology of the rock in study area, and combining with geological characteristics of iron ore deposits.Studies show that Tangquan granodiorite and quartz-monzodiorite are originated from the homologous magma, which have the characteristics of crust-mantle mixing, belong to metaluminum moderate K-high K calc-alkaline series. The LA ICP MS zircon U-Pb age of granodiorite is 160.06±0.83Ma. They form from active continental margin, and have relatives with mafic magma underplating of upper mantle in late Jurassic.Granodiorite and graniteporphyry of Gaoxing are derived from the homologous magma, which have the characteristics of crust-mantle mixing, belongs to weak peraluminum moderate K-high K calc-alkaline series. The diagenetic age of these two plutons is 151±Ma, both of which are originated from magmatism of late Jurassic, and form from active continental margin. Granite porphyry is apophysis of this pluton.By surveys of field and petrographic stdies, this paper considers that the orebody overlying strata of Gaoxing mine is Lindi formation (C1l) quartz glutenite of the lower carboniferous strata, which is a silicified alteration zone, and the alteration zone should belong to graniteporphyry and is formed by interaction with the wallrock. The bottom plate of orebody is Lindi formation (C1l) biotite-plagioclase granulitite which is actually mylonite, mainly composed of quartz, sericite and chlorite, and its protolith is argillaceous rock. So speculated that the rock of the bottom plate of orebody in Gaoxing mine may be overturned of original roof rock of orebody by tectonic activities, which is simultaneously mylonitic by the impact of the nappe tectonic.Combined with occurrence of field and LA ICP MS zircon U-Pb chronology of plutons, show that mineralization age of Tangquan iron ore should be earlier than 160.06±0.83Ma, mineralization age of Gaoxing iron ore should be earlier than 151Ma. The nappe tectonic of Gaoxing mine should be earlier than the age of the granite porphyry (150.74 ± 0.47Ma). Furthermore, the diagenetic age of granite porphyry in the Gaoxing mine is 150.74 ± 0.47Ma, which should be part of the Taihua complex massif presumably.Through analysis the petrographic and composition features of garnet skarn and magnetite in the mine, this paper considers that garnet skarn is magmatic skarn; magnetite of mine is not standard, but the iron oxide, which is rich in F, P etc al volatile and segregated from silicate magma. In summary, garnet and magnetite form from iron melten magma which is rich in volatile. Quartz-monzodiorite (Tangquan) and granodiorite (Gaoxing) have genetic relationship with Iron ore deposits of the study area.