湖南桃江地区金刚石指示矿物分布规律及异常特征——以金刚石、铬尖晶石及钛铁矿为例
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摘要
为进一步探索砂矿中金刚石的来源,寻找湖南地区原生金刚石,利用水系自然重砂方法在湖南桃江马迹塘地区共采集自然重砂测量样品250件,金刚石指示矿物种类较齐全,数量较多。其中发现金刚石12颗,类型较单一,粒径0.3mm左右,黄绿色、六-八面体;指示矿物铬尖晶石8864颗,黑色-灰黑色,磨损较强烈,呈浑圆粒状;钛铁矿2403颗,黑色-灰黑色,磨损较弱。通过区内金刚石及指示矿物分布特征,在区内划分出14个异常区,其中Ⅰ级异常区5个,Ⅱ级异常区5个,Ⅲ级异常区4个。金刚石及指示矿物分布广泛,但无定向富集,北部地区数量多、南部地区数量少,时间上老地层出露区数量多,新地层出露区数量少。通过金刚石及指示矿物对比研究发现,其晶形、颜色、粒度与桃江江石桥辉绿岩中的金刚石及宁乡钾镁煌斑岩中发现的金刚石特征相似,推测其来自区内尚未被发现的辉绿岩/钾镁煌斑岩等类型的岩体中。
In order to further explore the source of diamond in sand ore and search for primary diamond in Hu'nan Province, the authors used the natural heavy sand measurement method to collect 250 samples of natural heavy sand in Majitang area, Taojiang,Hu'nan Province. Diamond indicates quite a lot of minerals and much quantity. Twelve diamonds were found, which have a single type and are about 0.3mm in diameter, yellow green in color and exhibit hexoctahedron surface; there are 8864 grains of indicating mineral chromium spinels, black-grayish black in color, intensely worn, round granular in shape; there are 2403 grains of ilmenites,black-grayish black in color, relatively weakly worn. According to the distribution characteristics of diamonds and indicator minerals in this area, fourteen anomalous zones were delineated in the study area, including five grade Ⅰ anomaly area, five grade Ⅱ anomalyarea and four grade Ⅲ anomaly area. It is concluded that the distribution of diamond and indicating minerals in this area is extensive,but shows no orientation enrichment, the quantity of diamond in the northern region is large, whereas that in the southern region is small; the amount of the outcropped area in the old strata is large whereas that in the new strata is small. Through the comparative study of diamond and indicative minerals, it is found that the crystal shape, color and grain size are similar to the features of diamond in the Taojiang River stone bridge diabase and the diamond found in the Ningxiang potassium magnesium alloy. It is inferred that the minerals came from the diabase/potassium magnesia porphyry and other types of rock bodies that have not yet been discovered in this area.
In order to further explore the source of diamond in sand ore and search for primary diamond in Hu'nan Province, the authors used the natural heavy sand measurement method to collect 250 samples of natural heavy sand in Majitang area, Taojiang,Hu'nan Province. Diamond indicates quite a lot of minerals and much quantity. Twelve diamonds were found, which have a single type and are about 0.3mm in diameter, yellow green in color and exhibit hexoctahedron surface; there are 8864 grains of indicating mineral chromium spinels, black-grayish black in color, intensely worn, round granular in shape; there are 2403 grains of ilmenites,black-grayish black in color, relatively weakly worn. According to the distribution characteristics of diamonds and indicator minerals in this area, fourteen anomalous zones were delineated in the study area, including five grade Ⅰ anomaly area, five grade Ⅱ anomalyarea and four grade Ⅲ anomaly area. It is concluded that the distribution of diamond and indicating minerals in this area is extensive,but shows no orientation enrichment, the quantity of diamond in the northern region is large, whereas that in the southern region is small; the amount of the outcropped area in the old strata is large whereas that in the new strata is small. Through the comparative study of diamond and indicative minerals, it is found that the crystal shape, color and grain size are similar to the features of diamond in the Taojiang River stone bridge diabase and the diamond found in the Ningxiang potassium magnesium alloy. It is inferred that the minerals came from the diabase/potassium magnesia porphyry and other types of rock bodies that have not yet been discovered in this area.
引文
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[14]施倪承,陆琦,李国武,等.高铬刚玉:湖南沅水金刚石包裹体中发现的一种高压矿物[J].地学前缘,2011,18(6):341-346.
[15]曾祥清,郑云龙,杨志军,等.湖南扬子地台砂矿金刚石的红外、拉曼特征及指示意义[J].光谱学与光谱分析,2013,33(10):2694-2699.
[16]丘志力,王琦,秦社彩,等.湖南砂矿金刚石包裹体原位测试:对金刚石成因来源的启示[J].大地构造与成矿学,2014,38(3):590-597.
[17]金鑫镖,王磊,向华,等.湖南桃江地区印支期辉绿岩成因--地球化学、年代学和Sr-Nd-Pb同位素约束[J].地质通报,2017,36(5):750-760.
[18]刘训,李廷栋,耿树方,等.中国大地构造区划及若干问题[J].地质通报,2012,31(7):1024-1034.
[19]Scott-Smith B H,Skinner E M W,Loney P E.The Kapamba lamproites of the Luangwa valley,eastern Zambia[J].Proceedings of the Fourth International Kimberlite Conference.Geological Society of Australia Special Publication,1989,14(I):189-205.
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[21]Griffin W L,Jaques A L,Sie S H,et al.Conditions of diamond growth:A proton microprobe study of inclusions in West Australian diamonds[J].Contributions to Mineralogy and Petrology,1988,99(2):143-158.
[22]Collins,A T,Kanda H,Kitawaki H.Colour changes produced in natural brown diamonds by high-pressure high-temperature treatment[J].Diamond and Related Materials,2000,9(2):113-122.
[2]张培元.对湖南寻找金刚石原生矿的建议[J].中国地质,1998,(9)17-19.
[3]王道经,黄怀勇.撞击构造与金刚石--兼论湘西金刚石原生矿的找矿方向[J].大地构造与成矿学,1998,22(增刊):1-5.
[4]饶家荣.湖南原生金刚石矿深部构造地质背景及成矿预测[J].湖南地质,1999,18(1):21-28.
[5]杨明星,潘兆橹,郭孝明.湖南金刚石的红外光谱研究[J].宝石和宝石学杂志,2000,2(4):29-32.
[6]杨明星,潘兆橹.湖南金刚石内部不均一性特征研究[J].地质科技情报,2001,20(1):61-63.
[7]杨明星,高岩,湖南金刚石的褐斑特征及其意义[J].宝石和宝石学杂志,2002,4(4):15-19.
[8]杨明星,潘兆橹.湖南金刚石的显微塑性变形特征[J].地球科学-中国地质大学学报,2004,29(1):45-49.
[9]董斌,陈明珊,肖湘辉.湖南原生金刚石成矿地质背景及找矿方向[J].矿床地质,2006,25(增刊):337-340.
[10]董斌.湖南金刚石原生矿找矿工作与方向的再思考[J].国土资源情报,2009,(7):49-52.
[11]张令明,王三丁,肖湘辉,等.湖南原生金刚石矿形成条件探讨[J].国土资源导刊,2007,4(3):27-30.
[12]林玮鹏,丘志力,李子云,等.湖南宁乡Ⅴ号岩管煌斑岩的岩石地球化学特征[J].资源调查与环境,2009,30(3):180-187.
[13]黄自成,王华,方俊杰.湖南金刚石指示矿物特征[J].矿业工程研究,2010,25(3):64-67.
[14]施倪承,陆琦,李国武,等.高铬刚玉:湖南沅水金刚石包裹体中发现的一种高压矿物[J].地学前缘,2011,18(6):341-346.
[15]曾祥清,郑云龙,杨志军,等.湖南扬子地台砂矿金刚石的红外、拉曼特征及指示意义[J].光谱学与光谱分析,2013,33(10):2694-2699.
[16]丘志力,王琦,秦社彩,等.湖南砂矿金刚石包裹体原位测试:对金刚石成因来源的启示[J].大地构造与成矿学,2014,38(3):590-597.
[17]金鑫镖,王磊,向华,等.湖南桃江地区印支期辉绿岩成因--地球化学、年代学和Sr-Nd-Pb同位素约束[J].地质通报,2017,36(5):750-760.
[18]刘训,李廷栋,耿树方,等.中国大地构造区划及若干问题[J].地质通报,2012,31(7):1024-1034.
[19]Scott-Smith B H,Skinner E M W,Loney P E.The Kapamba lamproites of the Luangwa valley,eastern Zambia[J].Proceedings of the Fourth International Kimberlite Conference.Geological Society of Australia Special Publication,1989,14(I):189-205.
[20]Davies R M,Griffin W L,O'Reilly S Y,et al.Unusual mineral inclusions and carbon isotopes of alluvial diamonds from Bingara,Eastern Australia[J].Lithos,2003,69(1/2):51-66.
[21]Griffin W L,Jaques A L,Sie S H,et al.Conditions of diamond growth:A proton microprobe study of inclusions in West Australian diamonds[J].Contributions to Mineralogy and Petrology,1988,99(2):143-158.
[22]Collins,A T,Kanda H,Kitawaki H.Colour changes produced in natural brown diamonds by high-pressure high-temperature treatment[J].Diamond and Related Materials,2000,9(2):113-122.
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