承德千层背地区金属矿体成长特征及地质研究
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摘要
文章通过对承德千层背地区金属矿体中正长斑岩的年代学和地球化的研究,首次探讨了金属矿体中正长斑岩体的形成年代及成因。结果显示,正长斑岩体主量元素显示高硅、富碱的特征,属于准铝质—过铝质高钾钙碱性系列岩体;轻、重稀土元素分馏明显,具明显的负铕异常,岩体相对富集Rb、Th、La、Nd、Zr、Hf和LREE,相对亏损Ba、Nb、Sr、P、Ti。综合认为正长斑岩具有I型花岗岩的地球化学特征。该区正长斑岩锆石U–Pb测年结果显示岩体形成于134.30Ma±0.86Ma,为早白垩世产物。Hf同位素分析结果显示,?值介于-8.95471～15.7947之间,TDM2介于1749.925Ma～2182.814 Ma之间。表明金属矿体来源于2.0Ga左右的古老下地壳,形成于伸展环境。
By studying the chronology and geochemistry of syenite porphyry in the metal ore bodies in Qianbei area of Chengde, this paper discusses the syenite porphyry in the metal ore bodies for the first time.Formation age and genesis of rock mass. The results show that the major elements of syenite porphyry show the characteristics of high silicon and alkali, and belong to the quasi-aluminous-peraluminous high potassium calc-alkaline system.Lightweight and heavy REE fractionation is obvious and negative Eu anomaly is obvious. The rock mass is relatively rich in Rb, Th, La, Nd, Zr, Hf and LREE, and relatively deficient.Ba, Nb, Sr, P, Ti. It is considered that syenite porphyry has geochemical characteristics of type I granite.Zircon U-Pb dating of syenite porphyry in this area shows rock body shape.It was formed at 134.30 Ma(+0.86 Ma) and was a product of the Early Cretaceous. The ? results of Hf isotope analysis showed that the values ranged from-8.95471 to15.7947 and TDM2 from-8.95471 to 15.7947.Between 1749.925 Ma and 2182.814 Ma, it shows that the metal orebodies originated from the ancient lower crust of about 2.0 Ga and formed in an extensional environment.Keywords: metal ore bodies in the back of 1000 beds; syenite porphyry; zircon U-Pb dating; geochemistry; tectonic setting
By studying the chronology and geochemistry of syenite porphyry in the metal ore bodies in Qianbei area of Chengde, this paper discusses the syenite porphyry in the metal ore bodies for the first time.Formation age and genesis of rock mass. The results show that the major elements of syenite porphyry show the characteristics of high silicon and alkali, and belong to the quasi-aluminous-peraluminous high potassium calc-alkaline system.Lightweight and heavy REE fractionation is obvious and negative Eu anomaly is obvious. The rock mass is relatively rich in Rb, Th, La, Nd, Zr, Hf and LREE, and relatively deficient.Ba, Nb, Sr, P, Ti. It is considered that syenite porphyry has geochemical characteristics of type I granite.Zircon U-Pb dating of syenite porphyry in this area shows rock body shape.It was formed at 134.30 Ma(+0.86 Ma) and was a product of the Early Cretaceous. The ? results of Hf isotope analysis showed that the values ranged from-8.95471 to15.7947 and TDM2 from-8.95471 to 15.7947.Between 1749.925 Ma and 2182.814 Ma, it shows that the metal orebodies originated from the ancient lower crust of about 2.0 Ga and formed in an extensional environment.Keywords: metal ore bodies in the back of 1000 beds; syenite porphyry; zircon U-Pb dating; geochemistry; tectonic setting
引文
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[2]华仁民,毛景文.试论中国东部中生代成矿大爆发[J].矿床地质,1999(04):300-307.
[3]邵济安等,大兴安岭-燕山晚中生代岩浆活动与俯冲作用关系[J].地质学报,2001,75(1):56-63.
[4]吴福元,孙德有,等.中国东部中生代岩浆作用与岩石圈减薄[J].长春科技大学学报,1999,29(40):313-318.
[5]邓晋福.莫宣学,赵海玲,等.中国东部岩石圈跟/去跟作用与大陆“活化”[J].现代地质,1994,8:349-356.
[6]邓晋福,刘厚祥,赵海玲,罗照华,郭正府,李玉文.燕辽地区燕山期火成岩与造山模型[J].现代地质,1996(02):137-148.
[7]张旗.赵太平,王焰,等.中国东部燕山期岩浆活动的几个问题[J].岩石矿物学杂志,2001,20(3):273-292.
[8]翟明国等.华北克拉通中生代下地壳置换-非造山过程的壳幔交换[J].岩石学报,2002,18(01):1-8.
[9][68]徐一鸣.冀北千层背岩体岩石学、地球化学与锆石U-Pb年代学[D].中国地质大学,2016.
[10]朱弟成,莫宣学,王立全,赵志丹,牛耀龄,周长勇,杨岳衡.西藏冈底斯东部察隅高分异I型花岗岩的成因:锆石U-Pb年代学、地球化学和SrNd-Hf同位素约束[J].中国科学(D辑:地球科学),2009,39(07):833-848.
[11]吴福元,李献华,郑永飞等.Lu-Hf同位素体系及其岩石学应用[J].岩石学报,2007(02):185-220.
[12]Amelin Y,Halliday A N,Lee D C.Early-middle archaean crustal evolution deduced from Lu-Hf and U-Pb isotopic studies of single zircon grains[J].Geochimica Et Cosmochimica Acta,2000,64(24):4205-4225.
[13]Griffin W L,Wang X,Jackson S E,et al.Zircon chemistry and magma mixing,SE China:In-situ analysis of Hf isotopes,Tonglu and Pingtan igneous complexes[J].Lithos,2002,61(3):237-269.
[14]曲凯.太行山北段木吉村斑岩铜(钼)矿床地质特征与成矿作用[D].中国地质大学(北京),2012.
[15]赵振华.关于岩石微量元素构造环境判别图解使用的有关问题[J].大地构造与成矿学,2007,31(1):92-103.