湖南省新化县寒婆坳石墨矿床地质地球化学特征及控矿因素

Geological and Geochemical Characteristics and Ore Controlling Factors of Hanpoao Graphite Deposit in Xinhua County,Hunan Province

湖南省是我国隐晶质石墨最主要的矿产区,其隐晶质石墨的储量位居全国第一,主要是由煤系地层受接触热变质作用形成。本文以湖南省涟邵煤田北段寒婆坳石墨矿床为例,分析研究区内石墨矿床的地质地球化学特征与控矿因素。结果表明,矿石固定碳含量较高(>80%),矿石构造以块状为主,距花岗岩由近到远,石墨粒度逐渐变小。由上向下,接触热变质及石墨化的程度逐渐变大。寒婆坳石墨矿床碳质砂岩Al_(2)O_(3)、TFeO、Na_(2)O、K_(2)O、TiO_(2)含量相对较高,而围岩大理岩MgO、CaO含量相对较高;二者均表现出轻稀土富集、重稀土亏损的特点。碳质砂岩稀土元素总量较高,平均值为212×10^(–6),大理岩稀土元素总量较低,平均值为11.18×10^(–6);碳质砂岩具有明显的Eu、Pb、Sr负异常,U、Th、Ba正异常,Ce异常不明显。大理岩Cs、Pb为负异常,U为正异常,Sr异常不明显。寒婆坳矿区碳质砂岩主要形成于缺氧还原的环境,原岩沉积环境属于陆源海相沉积,物质来源于大陆碎屑物,位于滨浅海潮汐带沉积。测水组煤系地层、天龙山花岗岩体及寒婆坳推覆断层是本区石墨矿床的关键控矿因素。

Hunan Province is the most important mineral area of aphanitic graphite in China,and its reserves of aphanitic graphite rank first in China.It is mainly formed by contact thermal metamorphism of coal bearing strata.This paper taking the Hanpoao graphite deposit in the north of Lianshao coalfield as an example,and analyzed the geological,geochemical characteristics and ore controlling factors.The results show that the fixed carbon content of the ore is high(>80%),and the ore structure is mainly massive.The graphite particle size gradually decreases from near to far away from the granite,and the degree of contact thermal metamorphism and graphitization gradually increases from top to bottom.The content of Al_(2)O_(3),TFeO,Na_(2)O,K_(2)O and TiO_(2) in carbonaceous sandstone of Hanpoao graphite deposit is relatively high,while the content of MgO and CaO in marble is relatively high.Both carbonaceous sandstone and marble show the characteristics of LREE enrichment and HREE loss.TheΣREE in carbonaceous sandstone is high,with an average value of 212 Key words:aphanitic;graphite deposit;carbonaceous sandstone;geochemical;ore controlling factors×10^(-6),whereas theΣREE in marble is low,with an average value of 11.18×10^(-6);The carbonaceous sandstone has obvious negative anomalies of Eu,Pb and Sr,positive anomalies of U,Th and Ba,and Ce anomaly is not obvious.The marble Cs and Pb are negative anomalies,U is positive anomaly,and Sr anomaly is not obvious.The carbonaceous sandstone in Hanpoao mining area is mainly formed in the anoxic reduction environment.The sedimentary environment belongs to terrigenous marine sedimentation,and the material comes from continental debris,which is located in the coastal shallow sea tidal zone deposition.The coal bearing strata of Ceshui Formation,Tianlongshan granite and Hanpoao thrust fault are the key ore controlling factors of graphite deposits in this area.