| A series of celestite deposits in Mountains Huaying area is located in the Yangtze landmass under the third-grade tectonic unit detachmentfold belt in east Sichuan on tectonic. All the celestite deposits output in the Lower Triassic Jialingjiang Formation of carbonate rocks in Huaying Mountains. Through complex deposition, diagenesis and mineralization, as well as epigenetic mineralization and supergene transformation of geological processes.Celestite deposits in Huaying Mountains have been accumulated some geological exploration data since its discovery. There were many geologists carried out some scientific research works on the metallogenic geological conditions, deposit geology feature, main ore-controlling factors and puts forward some metallogenic model, but opinions differ. Thus, this paper aims to research the metallogenic geological background of celestite deposits in Huaying Mountains. The typical mineral deposits have been selected to research, except Yuxia celestite deposit in Tongliang County(the largest celestite deposits in China), Gongqiaoba celestite deposit in Dazhu County and Gangou celestite deposit in Hechuan County to master of celestite deposits' regional geological conditions and ore geological characteristics, ore body shape, occurrence and scale in metallogenic belt. In studying of the mineral assemblage, the texture and structure of the ores to master the sequence of mineral formation, thus mastering mineralization stage and metallogenic epoch of ore deposits, could help us to provide basic information for a correct understanding of celestite deposits in Huaying mountains' ore genesis.In stratigraphic division, the study region belongs to east Sichuan district of Yangtze stratigraphic region, the development of strata in this region is pretty good, which from the Cambrian to the Quaternary are all exposed. The structures in the regiona belong to Huaying Mountain anticline, the structures of mining area are also relatively simple, the main structure is the NE-SW Huaying Mountain fault zone and its derivative fault, in the northwestern of the anticline, several deposit are all produced. Just in terms of the mining area, the main structure is a monoclinal structure which is gently inclined towards northeast, almost no major fault across the mining area, and in the anticline axis, the strata's occurrence becomes steeper. Through the field geological investigation and sample collection about these several typical deposits in study region, this paper holds that in the study region, structures have little influence on celestite mine. Although there was vein celestite which is vertical to stratigraphic occurrence, it mainly is the product of the karstification. Karstification developed along the rock joints and fractures, and always co-existed with gypsum karst breccias or karst breccias closely.The main ore bearing strata of celestite deposits are Second Member of the Jialingjiang Formation and Fourth Member of the Jialingjiang Formation, the main ore bearing rock is a suit of thin layered-middle layered-thick-layered dolomite, dolomitic limestone, limestone, gypsum dolomite, gypsum karst breccias and karst breccias. The celestite orebody occurred as layer, layer-like and discontinuous layer,in some ore section it also occurred as veinlet and big vein along the bedding, parts orebody occurred as veinlet and reticulate veins which is vertical to bedding, and some area also exist brecciated ore which is cut through layer. The structures of the ore are mainly include idiomorphic, hypidiomorphic-idiomorphic and anhedral-idiomorphic granular structure fine and have grain, middle grain and coarse grain celestite. The texture of ore is mainly layered structure, stripe structure, banded structure and a few veinlet structure, thick vein structure and miarolitic structure. The occurrence of ore is completely consistent with the occurrence of strata, horizontal bedding, Large tabular cross bedding, contemporaneous fold and crumple structure are also existed in celestite ore.In the underground mine of Yuxia mining area, we find that the layer and thin layer tabular cross-bedding are both composed of celestite, which proves that the celestite deposit is a product of sedimentation.Based on the analyses of predecessors' research data, as the strata condition,the Second and the Fourth segment Jialingjiang Formation are the main ore-hosting layers of the strontium mine. The content of the strontium in the strata is significantly higher than the earth's crust Clark Vaule. The total thickness of the ore-hosting strata can reach 266-397 meters,stably distributing along the whole Huaying Mountains structure. As the lithofacies conditions, the formation of the celestite ores in the Huaying Mountain areas is restricted by the Sabkha paleogeographic environment, and regionally, celestite deposits(ore occurrences) and mineralized spots of Yuxia in Tongliang, Gulong in Dazu, Gangou in Hechuan, Gongqiaoba in Dazhu, Wangxi and Longmenxia in Qu County and so on occurred in a set of carbonate rocks fromed in the Sabkha paleogeographic environment. Through the lithofacies paleogeographic study, this paper finds that the Sabkha environment in the early Triassic Jialingjiang period(T1j2) is especially developed, from the evolution of the carbonate sedimentary stage to the sulfate deposition stage in the sea basin. Such a large area Sabkha environment distributed prompts the transition from the calcite, dolomite deposit to gypsum, polyhalite, celestite ore deposit. It is confirmed that the celestite ore deposits intensively distribute in the Huaying Mountain anticlinal structural belt.This thesis studies suggest that the ore genesis of celestine ore in Huaying Mountain region is a typical kind of vapor deposition(salt) deposit. From the formation, transformation and preservation of the deposit, the mineralization stages can be divided into the three stages: synsedimentary mineralization, after generating rocks-mineralization and alteration stage, supergene alteration stage. In the sedimentary-diagenesis-mineralization stage, with the process of the increase of marine basin and seawater's salinity on the early Triassic in Sichuan, the content of the Sr2+, SO42- became supersaturated. Therefore, the celestine crystals precipitated in this process, and finally formed a large-scale distributed celestine ore. Epigenetic mineralization stage: primary sedimentary celestite seam is thickening with depth of burial increasing affected by the geothermal temperature and pressure. Especially when decollement fault was formed, basinal water dissolved some celestite by circulation, leading to part of the Sr element migrating, and forming underground hypothermy mineral-bearing liquor. They filled decollement layer between layers, rittle shear zone, crevice and structural taconite by metasomatism and filling metasomatism, produced some veinlets, mesh-vein, rough vein of celestite ore bodies. Although having small scale, they can cut across stratum and thread layer. Therefore, anadiagenesis and epigenetic mineralization have happened alteration to celestite ore bodies, not the main mineralization of Huaying Mountain celestine deposit. The part of celestine ore body in the supergene period being transformed: in the supergene stage,ore body relative rise to near surface or part of ore body exposed to the ground surface, under the influence of precipitation and rich in CO2 and HCO3- gas saturated with groundwater, celestine ore can be converted to strontium, Sometimes it can be leached down along the rock fissures formed strontianite. |
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