冀西北地区古元古代含石墨变质地层岩石矿物地球化学特征与成矿机制研究

冀西北地区已发现多处大、中型晶质石墨矿,具有良好的区域变质石墨矿成矿地质条件与找矿潜力。古元古代红旗营子岩群太平庄岩组、东井子岩组和集宁岩群下白窑岩组为该地区重要的成矿层位,本文对这些含矿地层岩石进行了详细的岩相学及地球化学等方面的研究,并对石墨矿成因机制进行了探讨。研究结果表明,红旗营子岩群含矿岩石为石墨石榴黑云斜长片麻岩,其原岩是以泥岩、黏土质砂岩、砂岩及碳酸盐岩为主的岩石组合,局部富含有机质,表明这些含碳岩石的成熟度较高,为温暖潮湿-半干燥气候条件下海陆交互-滨浅海相沉积;集宁岩群下白窑岩组含矿岩石为石墨石榴斜长变粒岩,其原岩是以内陆湖-滨浅海相沉积的成熟度较高的泥岩、黏土质砂岩、砂岩、石英砂岩为主的岩石组合,局部富含有机质,形成于半干燥-干燥炎热气候下氧化-弱氧化沉积环境,在沉积过程中伴有热水参与。石墨矿碳质成分均来源于原岩本身的原始沉积的有机碳。矿床受层位、岩相和岩性控制,经区域变质作用,有机碳结晶形成石墨矿,并在断裂的控制下出露于地表或近地表。

Geochemical characteristics and metallogenic mechanism of the Paleoproterozoic graphite-bearing metamorphic strata in Northwestern Hebei Province

Many large and medium crystalline graphite deposits have been found in Northwestern Hebei Province, with good metallogenic geological conditions and prospecting potential of regional metamorphic graphite deposits. Taipingzhuang Formation and Dongjingzi Formation of the Hongqiyingzi Group and Xiabaiyao Formation of the Jining Group in the Paleoproterozoic are important metallogenic horizons in this area. This paper has carried out a detailed petrographic and geochemical study of these ore-bearing strata, and discussed the metallogenetic mechanism of graphite deposits. The research results show that the ore-bearing rock of the Hongqiyingzi Group is graphite garnet biotite plagiogneiss, and the original rock is mainly composed of mudstone, clay sandstone, sandstone and carbonate rock, which are locally rich in organic matter, indicating that the maturity of the carboniferous rocks is generally higher, and the clastic rocks have been deposited in the marine-continental interaction and shallow marine facies under the warm humid and semi-dry climate. The ore-bearing rock of Xiabaiyao Formation of the Jining Group is graphite garnet plagioclase granulite, and the proto-rock is mainly composed of mudstone, clay sandstone, sandstone and quartz sandstone with higher maturity of littoral-shallow sea-inland lacustrine sedimentary facies, and are locally rich in organic matter, and formed in the oxidation-weak oxidation sedimentary environment under the semi-dry and dry climate, accompanied by hot water in the deposition process. The carbonaceous components of graphite ore were all derived from the original organic carbon deposited in the original rock itself. The deposit was controlled by horizon, lithofacies and lithology. Through regional metamorphism, organic carbon crystallized to form graphite ore, which was exposed to the surface or near the surface under the control of faults.