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Li W.,Chinese Academy of Geological Sciences | Li W.,Wuhan University | Xie G.,Chinese Academy of Geological Sciences | Xie G.,MLR Key Laboratory of Metallogeny and Mineral Assessment | And 4 more authors.
Yanshi Xuebao/Acta Petrologica Sinica | Year: 2016

The Chengchao iron deposit, located in the southeastern Hubei Province, is the largest skarn iron deposit in the Middle-Lower Yangtze River Valley metallogenic belt (MLYRB) and most orebodies distributed along the contact zones between the Early Cretaceous intrusions and Triassic strata. To further investigate the deposit formation mechanism, in this contribution, detailed field and microscope observation of magnetite have been focused on various locations and occurrence of ores and mineralized skarn as well as magnetite in the intrusions. And four generations magnetite has been identified in different types of ores and mineralized skarn. The earliest generation magnetite (Mtl) is heterogeneous and undergone dissolution-reprecipitation process. The second generation magnetite (Mt2) is homogeneous and develops in oscillatory texture. The third generation magnetite (Mt3) is characterized with homogeneous and absence of oscillatory texture. The last generation magnetite (Mt4) shows dendrite and xenomorphic granular texture, and lack of oscillatory texture. EMPA data reveal that big compositional variations are existed among them, predominantly for the high concentration elements Si, AI, Ca, Mg, while differences for low content elements Ti, Cr, V, Zn, Ni are relatively small. Factors, such as fluid oxygen fugacity, temperature, concentration of elements, water-rock reaction may jointly account for the differences. Compared with multiple generations magnetite, those within intrusions, not only the texture, but also the compositon, especallly for Ti content, show large differences. Based on the above analysis, and considering the difference with other types magnetite, we purposed that the magnetite in Chengchao is of hydrothermal origin rather than magmatic. According to the semi-quantitative simulation calculation results, the former three generations magnetite contribute more than 96% Fe and paly a crucial role for the forming of Chengchao iron deposit. Superimposed mineralization process provide a deeper understanding for the ore genesis of Chengchao iron deposit, and give an inspiration for the enrichment mechanism of skarn-type iron deposits.

Dai J.-J.,Chinese Academy of Geological Sciences | Dai J.-J.,MLR Key Laboratory of Metallogeny and Mineral Assessment | Dai J.-J.,China University of Geosciences | Wang D.-H.,Chinese Academy of Geological Sciences | And 5 more authors.
Acta Geoscientica Sinica | Year: 2013

The mining of rare earth ore leads to a series of environmental problems. To solve the problem of environmental monitoring of the ion-absorbed rare earth ore districts in southern China, the authors selected Xunwu area in south Jiangxi as the study area, and used IKONOS remote sensing data for investigation. For the two main kinds of environmental problems in the ion-absorbed rare earth ore mining, i.e., land desertification and water pollution, the spectral angle mapping classification method was chosen to extract the land desertification place in the study area, and ISODATA unsupervised classification algorithm was used to estimate the contamination of the river near the ion-absorbed rare earth ore district. An analysis of the results and field survey show that high spatial resolution remote sensing technology can provide a good means for environmental investigation of the ion-absorbed rare earth ore district.

Bo Y.,MLR Key Laboratory of Metallogeny and Mineral Assessment | Bo Y.,Chinese Academy of Geological Sciences | Liu C.-L.,MLR Key Laboratory of Metallogeny and Mineral Assessment | Liu C.-L.,Chinese Academy of Geological Sciences | And 3 more authors.
Acta Geoscientica Sinica | Year: 2013

In this paper, hydrochemical characteristics and origin of saline springs/brines in southwestern and northern Tarim Basin were studied, ionic ratios were discussed, and a corresponding indicator system was suggested for potassium exploration. Analytical data of 194 saline spring/brine samples were obtained from both field survey and geochemical materials available. It is found that saline springs/brines in southwestern Tarim Basin (Shache Basin, a sub-basin) mainly belong to the sulfate type, with a few belonging to the chloride type, while in northern Tarim Basin (Kuqa Basin, a sub-basin), the chloride type is dominant, followed by the sulfate type. Evolution processes of saline springs/brines in this area are very complicated, consisting of recharge from the depth of the earth, water-rock salt interaction, inflow of surface water and strong evaporation. As for potassium exploration, the potassium-to-chloride ratio, the magnesium-to-chloride ratio, the sodium-to-chloride ratio and the boron-to-chloride ratio can well serve as indicators for potassium deposit prediction instead of the bromine-to-chloride ratio and the potassium-to-bromine ratio, due to the paucity of bromine in the basin. The determination of environmental background values for chemical components, TDS and ionic ratios can provide useful information and references for potassium exploration in the Tarim Basin as well as in other saline basins of China.

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