河北省北部晶质石墨矿层岩(矿)石地球化学特征与成因分析
投稿时间:2023-04-27  修订日期:2023-07-23  点此下载全文
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翟大兴* 河北省地球物理勘查院(河北省浅层地热能研究中心) 06500
基金项目:河北省地矿局地勘基金项目“冀北地区红旗营子岩群晶质石墨矿床成矿规律与找矿方向研究”资助
中文摘要:晶质石墨是一种新兴战略矿产。近年在河北省北部发现了多处大中型晶质石墨矿床,主要赋矿层位新太古代崇礼上岩群、古元古代红旗营子岩群等,具有良好的成矿潜力。通过系统的野外地质调查与采样、分析测试工作,详细研究了赋矿层位的岩相学、地球化学特征,并对碳质来源进行了分析。结果表明:赋矿岩石主要为含石墨黑云斜长变粒岩、片麻岩与透辉岩,原岩恢复以砂泥质碎屑岩、钙质沉积岩为主。主量元素变化较大,SiO2含量为38.90%~80.42%, CaO+MgO为2.65%~31.93%, Al2O3为1.50%~15.34%;稀土元素含量为79.1μg/g~321.4μg/g,PAAS标准化分布模式一般具有右倾或较平坦分布特征,δCe略具负异常,部分具有δEu异常。微量元素特征指示沉积环境为滨浅海环境,部分地区存在富氧条件,局部为还原环境或存在热液加入。石墨中碳同位素值为-20.7‰~-26.0‰,主要来源于生物成因有机碳;大理岩碳同位素值为-3.8‰~1.1‰,主要来源于碳酸盐岩成因无机碳。区内晶质石墨矿层分布受到地层、岩性、岩相控制,含矿有利层位为古陆边缘滨浅海相富含有机质的砂泥质碎屑岩、钙质沉积岩。矿床成因为沉积变质型矿床。
中文关键词:华北板块北缘  石墨矿  地球化学  微量元素  碳同位素
 
Geochemical characteristics and genesis of crystalline graphite ore bed rocks in northern Hebei Province
Abstract:Crystalline graphite is an emerging strategic mineral. In recent years, several large and medium –sized crystalline graphite deposits have been found in northern Hebei Province, with great mineralization potentiality in this area. The main ore bearing horizons are Neoarchean Upper Chonglishang Group and Paleoproterozoic Hongqiyingzi Group, etc.. Through systematic field geological survey, sampling, analysis and testing, the petrography and geochemical characteristics of the ore bearing horizon were studied in detail, and the carbon source was analyzed. The results show that the main host rocks are graphite bearing biotite plagioclase granulite, graphite bearing biotite plagioclase gneiss and graphite bearing biotite plagioclase diopside. The proto-rocks restoration are mainly composed of argillaceous clastic rocks and calcareous sedimentary rocks. The main elements in graphite bearing strata vary greatly, with SiO2 content of 38.90%~80.42%, CaO+MgO of 2.65%~31.93%, and Al2O3 of 1.50%~15.34%. The content of rare earth elements is 79.1 μg/g~321.4 μg/g. PAAS standardized distribution pattern generally has the characteristics of right leaning or relatively flat distribution. Some samples have slightlyδCe negative anomaly and δEu anomaly. The characteristics of trace elements indicate that the sedimentary environment is a coastal and shallow sea environment, with oxygen rich conditions in some areas, reduction environment or hydrothermal addition in some areas. The carbon isotope value of graphite is -20.7‰~-26.0‰, which mainly comes from biogenic organic carbon. The carbon isotope value of marble ranges from - 3.8 ‰ to 1.1 ‰, mainly derived from inorganic carbon of carbonate origin. The crystalline graphite ore bed in the area is controlled by stratum, lithology and lithofacies. The favorable ore bearing horizon is sandy argillaceous clastic rock and calcareous sedimentary rock rich in organic matter in the coastal shallow sea facies of the ancient continental margin. The deposit is a sedimentary metamorphic deposit.
keywords:Northern margin of North China Plate  Graphite ore  Geochemistry  Trace element  Isotope of carbon
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