Study On The Geoglogical Characteristics And Exploration Directions Of Gold Mineralization In Pengboshan Area, Ejinaqi County, Inner Mongoulia

The study area in Ejinaqi of Alashan Union of Inner Mongolia is located at thesoutheastern part of Central Asia desert, near the northern margin of Jilin desert atBadan. The tectonic position is in the eastern Tianshan–Yinshan structure belt withWE trending and Tianshuijing–Wuzhuergashun–Yagan metallogenic belt.From May2010to October2010and May2011to November2011, respectively, theauthor investigated the study area. The major work were measurement of1:25000soilgeochemistry,1:25000simply geological measurement,1:10000soil geochemistryprofiles of which are31.54Km long and trenching of2032M³and so on. We selected3354samples of soil geochemistry, analyzed87petrochemistry samples, identified125thin sections and tested7inclusions. Based on our field and measurement workfrom2010to2011, we suggested that:1. The Lower Carboniferous Baishan group （C₁b₁） and Lvtiaoshan group （C₁l）arethe main strata in the study area. In northeastern part, we found the Early PaleozoicBeishan group （Pt₁b）,which are consisted mainly of plagioclase gneiss. It has neverbeen mentioned in the past regional references. Fault structures in the region werewell developed and the scale is relatively large. The most important fault throughoutsouth central research area is Shikuaishan-Pengboshan thrust fault, the main trend is270-290°, dig angle is60-70°and the direction is northward. A series of N-Sextensional faults and extensional-shear faults and shear faults with NW and NEtrends are subordinate. Magmatic rocks mainly distributed in the northern, southernand eastern margin. Intrusive rocks dominated by the Variscan diorites can be foundon both sides of the large faults. Diorites are characterized by batholiths and stock.2. The major ore-forming element of study area was identified as gold, notcopper-multielements. However, the gold mineralization type of study area isrelatively single, mainly the type of quartz vein that is our object research. Partly quartz veins are intensive, and the features are higher gold grade and some level ofscales. Quartz veins are generally controlled by the subordinate fractures of footwallsof main faults, and the mineralization types are siliconization, pyritization and so on.Based on the results of slot work, we divided the quartz veins into8places in ourstudy area. The grade is greater than0.1g/tons. All the veins distribute in the north andsouth sides of ductile shear zones which traversed our study area, and NW trending.3. According to study on the fluid inclusions of quartz veins, our results indicatedthat fluid inclusions can be divided into two types: two-phase inclusions of gas-liquidand three-phase inclusions combined with CO₂. The former one is dominated,accounting for more than80%. The major fluid salinity is2.23-9.86wt%NaCl.Uniform temperature range of inclusions is182–300℃. Testing results of fluidinclusions show that the ore-forming of veins is NaCI-CO₂-H₂O system, and thesalinity is low. We preliminary suggested that the source of fluid are probably relatedto magmatic water and the earlier stage of ore forming is mainly magmatic afterheateffect because the ore veins distribute in the contact part between stratum and dioritebody. Scatter diagram of uniform-salinity shows the density of ore-forming fluid is0.70-0.95g/cm3, the main density range are0.85-0.90g/cm3, therefore, theore-forming fluid is low density type, preliminarily indicating that the later stage ofore-forming is related to atmospheric precipitation.4. We analyzed the soil geochemistry data of study area and found66multi-element anomalitic places. There are7abnormal places of Au. Youwanganomalous is Au-HT10-4, Au-HT10-5, Au-HT10-6and Au-HT10-7, respectively.They all belong to A-class anomaly. Based on the overlap situation amongmulti-element anomaly, our study area can be divided into four places of assemblageanomaly. These places are characterized by large scale, high intensity, and favorableore-forming geological condition and well developed quartz veins in abnormal places.Based on the measurement of partly explosive electron middle grad sections anomaly,our study area can be divided into nine high resistance belts.5. Combined with soil geochemistry anomaly of Au, assemblage anomaly of soilgeochemistry, locations and anomaly features of explosive electron middle gradsections anomaly, relationship among anomaly, geological body and ore-vein,geological condition, we chose three prospecting target zones in our study area.6. In order to further confirm the prospecting target zones, we chose VI and VIIveins at No.3target zone and operated drilling engineering, and the drills were marketed as ZK009and ZK007. Drill of ZK009was designed for VI vein. Its depth is215M. This drilling can be divided into19layers. It is easy to find the phenomenonof siliconization, sericitization and chloritization on mineralized zones the mainmineralization types of which are limonitization and pyritization. We selected andtested56samples. The gold grade of samples is0.05-0.47g/t. Drills of ZK007is100M from the ore-vein of VII. The depth is200M. This drill can be divided into17layers. The main mineralization types are limonitization and pyritization. Testingresults of122samples show that the gold grade is0.05-2.66g/t.Our results from drilling engineering fully verified the reasonable of prospectingtarget zones, confirmed that the study area has a good mineralization prospect andprovided a strong evidence for future prospecting work...