Study On The Gensis Of Bauxite Ore In Benxi Formation In Yanlong Area, Western Henan

Taking Al-bearing rock series as study sample in Benxi Formation, Yanlong Area, Western Henan, detailed observation were conducted for the 36 open pit of bauxite in eastern and northeastern of the study area and as many as 110 ore-bearing cores of bauxite hole spacing by 400m×260m in the study area, characteristics of mineralogy, geochemistry and macro sedimentary in the vertical change have been analyzed by rock thin section, SEM, EDS, X-ray diffraction,cathodoluminescence images of zircons andisotopic dating, as well as differential thermal and infrared spectrum, based on the analysis of the above, combining with the distribution of the base Paleokarst to analyze the gensis of Al-bearing series in Benxi Formation in Yalong area,Western,Henan.According to the analyse of mineral characteristics and basic principle of chemical weathering of mineral during the hypergeneweathering process, We think that the volcanic ash which possessed huge specific surface and was easy to hydrolyze may be the protolith of the Al-bearing series. Analyze of the geochemistrycharacteristics on the vertical of the Al-bearing series show that all the Al-bearing series suffered intense weathering during its formation, we think that the original rock suffered chemical weatheringmainly by leaching hydrolysis under good drainage conditions when associating with sedimentary background and basement carbonate of the Al-bearing series. Illite in the lower mudstone may be formed by the K–bentonite which was hydrolyzed by volcanic ash in alkaline environment of marine during burial process in the late stage. Kaolinite in the upper mudstone may be formed by tonstein which was also hydrolyzed by volcanic ashin the acidic marsh environment.The formation of ore-bearing rock series has relationship with the change of sedimentary environment for the hydrolyzed of volcanic ash, Analysis of substrate paleokarst of the surface showed that the occurrence of orebody also controlled by karstification during syndepositional stage at the same time, and the karstificationcontrolled by joints along NW and NEE trending, it was mainly controlled by the tectonic principal stress along nearly east-westward during the mineralization period, which was different from north-south before the mineralization period, so,we hypothesized that changes of maximum principal stress during the sedimentation of Benxi Formation might be the tectonic setting condition of the formation of the ore-bearing rock series.