徐州北部西村苦橄玢岩地球化学特征及其与金伯利岩的对比
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摘要
在江苏北部寻找金刚石原生矿的过程中,于徐州北部西村发现18条苦橄玢岩脉(管)。研究发现,在岩石地球化学方面,该区苦橄玢岩与山东、辽宁等地区的金伯利岩具有相似性:二者均属偏碱性超基性岩,徐州西村苦橄玢岩以MgO含量低,Al_2O_3、CaO、K_2O含量偏高,w(Fe~(3+))/w(Fe~(2+))比>1为特征,与碳酸盐化金伯利岩的地球化学特征相似;二者的过渡族金属元素球粒陨石标准化配分曲线均为"M"型,且以显著的Ti、Nb正异常及陡倾斜为特征,稀土元素球粒陨石标准化配分曲线均显示轻稀土相对富集、重稀土相对亏损;辽宁、山东地区金伯利岩富集Nb,Nb与Cr、Ni、Co等呈正相关,而徐州西村苦橄玢岩中的Nb则与Cr、Ni、Co等呈负相关。这些地球化学特征说明,徐州西村苦橄玢岩与辽宁、山东地区的金伯利岩具有一定的成因联系,为该区金刚石找矿提供了有利线索。
In prospecting primary diamond deposits,we discovered 18 picrite-porphyrite dykes in Xicun Village,north of Xuzhou.Xicun picrite-porphyrite shares many geochemical similarities with the kimberlite in Shandong and Liaoning provinces.These rocks are all alkali ultra-basic rocks and Xicun picrite-porphyrite has similar chemical compositions(low w(MgO);high w(Al_2O_3),w(CaO),w(K_2O),w(Fe~(3+))/w(Fe~(2+))> 1)with carbonatite kimberlites.Their chondrite-normalized distribution curves of transition metal elements are M-shape and display significant positive anomalies of Ti and Nb and sharp dip.Chondrite-normalized REE distribution patterns display strong enrichment of LREE and relative depletion of HREE.The kimberlites in Shandong and Liaoning are characterized by enrichment of Nb and show positive correlation of Nb with Cr,Ni and Co,whereas the picrite-porphyrite in Xicun have low Nb content and show negative correlation of Nb with Cr,Ni and Co.These geochemical characteristics indicate a likely genetic relationship between the picrite-porphyrite and kimberlites,which has significance for prospecting of diamond.
In prospecting primary diamond deposits,we discovered 18 picrite-porphyrite dykes in Xicun Village,north of Xuzhou.Xicun picrite-porphyrite shares many geochemical similarities with the kimberlite in Shandong and Liaoning provinces.These rocks are all alkali ultra-basic rocks and Xicun picrite-porphyrite has similar chemical compositions(low w(MgO);high w(Al_2O_3),w(CaO),w(K_2O),w(Fe~(3+))/w(Fe~(2+))> 1)with carbonatite kimberlites.Their chondrite-normalized distribution curves of transition metal elements are M-shape and display significant positive anomalies of Ti and Nb and sharp dip.Chondrite-normalized REE distribution patterns display strong enrichment of LREE and relative depletion of HREE.The kimberlites in Shandong and Liaoning are characterized by enrichment of Nb and show positive correlation of Nb with Cr,Ni and Co,whereas the picrite-porphyrite in Xicun have low Nb content and show negative correlation of Nb with Cr,Ni and Co.These geochemical characteristics indicate a likely genetic relationship between the picrite-porphyrite and kimberlites,which has significance for prospecting of diamond.
引文
蔡逸涛,陈国光,张洁,等,2014.安徽栏杆地区橄榄辉长岩地球化学特征及其与金刚石成矿的关系[J].资源调查与环境,35(4):245-253.
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施建斌,曹强,蔡承刚,2010b.江苏新沂金刚石砂矿地质特征及供源方向探讨[J].化工矿产地质,32(1):39-43.
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杨经绥,徐向珍,李源,等,2011.西藏雅鲁藏布江缝合带的普兰地幔橄榄岩中发现金刚石:蛇绿岩型金刚石分类的提出[J].岩石学报,27(11):3171-3178.
杨经绥,徐向珍,白文吉,等,2014.蛇绿岩型金刚石的特征[J].岩石学报,30(8):2113-2124.
周秀仲,杨建民,黄蕴慧,等,1990.山东和辽宁金伯利岩的稀土元素地球化学特征[J].岩石矿物学杂志,9(4):300-308.
张培元,1998a.积极探索突破新类型金刚石原生矿床[J].地质科技管理,15(5):1-8.
张培元,1998b.有关金刚石成因等若干重大问题的新认识[J].湖南地质,17(3):204-210.
宗德林,高荣秀,宗元春,2014.徐州潘塘盆地地热地质条件分析及热储靶区预测[J].能源技术与管理,39(6):142-145.
张洁,蔡逸涛,董钟斗,等,2015.安徽栏杆金刚石矿物特征及其寄主母岩地球化学特征研究[J].宝石和宝石学杂志,17(5):1-11.
张洁,吕凤军,蔡逸涛,等,2016.安徽栏杆碱性基性岩型金刚石矿遥感影像特征[J].宝石和宝石学杂志,18(4):1-9.
KOGARKO L N,RYABCHIKOV I D,2013.Diamond potential versus oxygen regime of carbonatites[J].Petrology,21(4):316-335.
蔡逸涛,张洁,2015.安徽栏杆含金刚石母岩岩石学特征[J].地质论评,61(增刊1):608-609.
董振信,1994.中国金伯利岩[M].北京:科学出版社:1-30.
黄蕴慧,秦淑英,周秀仲,1992.华北地台金伯利岩与金刚石[M].北京:地质出版社:1-54.
贺世杰,2003.徐州地区晚元古代辉绿岩墙岩石成因的初步研究[D].广州:广州地球化学研究所.
李昌年,1991.几种含金刚石岩系及相关岩石的地球化学性质[J].地质科技情报,10(增刊1):85-96.
戎合,杨经绥,张仲明,等,2013.西藏罗布莎橄榄岩与中国大陆科学钻探主孔(CCSD-MH)榴辉岩中金刚石的红外特征初探[J].岩石学报,29(6):1861-1866.
施建斌,2009.江苏新沂南部地区玻璃用石英砂矿成矿规律研究[J].地质学刊,33(3):272-276.
施建斌,蔡承刚,曹强,2010a.江苏沛县姜梨园铁矿矿床成因及找矿方向[J].有色金属:矿山部分,62(2):31-34.
施建斌,曹强,蔡承刚,2010b.江苏新沂金刚石砂矿地质特征及供源方向探讨[J].化工矿产地质,32(1):39-43.
施建斌,卢爱冬,钱静,等,2012.徐州市铜山区山体地质环境综合评价[J].地质灾害与环境保护,23(2):36-39.
杨经绥,徐向珍,李源,等,2011.西藏雅鲁藏布江缝合带的普兰地幔橄榄岩中发现金刚石:蛇绿岩型金刚石分类的提出[J].岩石学报,27(11):3171-3178.
杨经绥,徐向珍,白文吉,等,2014.蛇绿岩型金刚石的特征[J].岩石学报,30(8):2113-2124.
周秀仲,杨建民,黄蕴慧,等,1990.山东和辽宁金伯利岩的稀土元素地球化学特征[J].岩石矿物学杂志,9(4):300-308.
张培元,1998a.积极探索突破新类型金刚石原生矿床[J].地质科技管理,15(5):1-8.
张培元,1998b.有关金刚石成因等若干重大问题的新认识[J].湖南地质,17(3):204-210.
宗德林,高荣秀,宗元春,2014.徐州潘塘盆地地热地质条件分析及热储靶区预测[J].能源技术与管理,39(6):142-145.
张洁,蔡逸涛,董钟斗,等,2015.安徽栏杆金刚石矿物特征及其寄主母岩地球化学特征研究[J].宝石和宝石学杂志,17(5):1-11.
张洁,吕凤军,蔡逸涛,等,2016.安徽栏杆碱性基性岩型金刚石矿遥感影像特征[J].宝石和宝石学杂志,18(4):1-9.
KOGARKO L N,RYABCHIKOV I D,2013.Diamond potential versus oxygen regime of carbonatites[J].Petrology,21(4):316-335.