Geochemical Characteristics Of The Tou Tianmen Greisen Type Tungsten Deposit In The Bai Yunxian Ore Fields, Hunan Province

The Bai Yunxian tin-tungsten polymetalic ore field in Hunan province locates inthe eastern part of Nanling depression belt in Hercynian period is an important part ofthe Nanling metallogenic belt. This ore field is closely related to the formation anddistribution of a wide range of Mesozoic granite. Main deposit in granite rock mass ormore and contact zone of surrounding rock, for the study of the system provides theMesozoic tectonic evolution and large-scale metallogeny in advantageous conditions.It focuses on the Tou Tianmen tungsten deposit in Hunan province. The regionalore deposits comparison, mineralogy, petrology, ore deposit geology andgeochemistry, and mineralization fluid have been studied to explore the cause ofdeposit type and prospecting mark. The above methods are used to: summarize theore-forming geological background; summarize the law applicable to themineralization in the Tou Tianmen deposit; make prediction and prospection in thedeep and margin of the Tou Tianmen deposit. Considerable progress has been made inthe following aspects:(1) Tou Tianmen tungsten deposit metallogenic geologic body for mineralizationgranite rock wall, mineralization area all greisenization, the stronger thegreisenization mineralization, the better. System of constant and trace elementgeochemical study shows that mineralization granite rock wall with rich silicon;aluminum supersaturated rich alkali and so on, so long as alkali granite,characteristics and the Nanling region associated with vein type tungsten long alkaligranite, mineral enrichment is closely related to granitic magmatism.(2) The failure of granite predecessors as the fine grained porphyritic granite,according to the value of albite in the granite, reclassify it as a fine grained porphyriticalkali granite. The alkali granite formed by magma that are rich in volatile,immiscible effect of liquid widely development in rock mass near the top, is the maindifferentiation of the enrichment of tungsten polymetallic mineralization. The value ofalbite in the granite can be part of the sodium feldspar as one of the symbols of granite mineralization properties evaluation.(3) The mineralization granite rock wall has the schlieren of greisens. Throughthe integrated analysis of the greisen’s schlieirens, it is concluded that the formationof the greisen’s schlieirens are affected by the joint effect of magma and hydrothermalfluid. The schlieirens of greisens are formed by the fluid-liquid phase differentiationevolution of magma-hydrothermal transitional state between magma andhydrothermal fluid.To sum up, the ore body of granite rock wall of the Tou Tianmen tungstendeposit has the characteristics of magma and hydrothermal fluid, is a kind of fluid inbetween magma fluid and hydrotherm, and is the main metallogenic period ofscheelite.