投稿时间：2018-07-23
修订日期：2019-04-15
网络发布日期：2019-12-24
中文摘要:东秦岭钼矿带蟒岭矿集区南部侏罗系华阳村组底部出露一套粗面英安岩，对其进行LA-ICP-MS锆石定年，测得锆石206Pb/238U年龄为（150.92±0.70）Ma（95%置信度；MSWD=0.19），表明其形成于晚侏罗世。地球化学特征显示该岩石类似于中国东部燕山期C型埃达克质岩，表现为高硅（w（SiO2）=59.75%~60.97%）、铝（w（Al2O3）=15.84%~16.01%）、钾（w（K2O）=3.74%~3.89%）、锶（w（Sr）=286×10-6~338×10-6），高Sr/Y比值（20.85~24.53），低镁（w（MgO）=2.37%~2.66%）、镱（w（Yb）=1.30×10-6~1.50×10-6）、钇（w（Y）=13.3×10-6~15.4×10-6），重稀土元素明显亏损，轻重稀土元素分异明显（LREE/HREE=10.27~12.25），具有弱的正Eu异常（1.21~1.37），大离子亲石元素如Rb、Ba、Sr、U、K富集，相对亏损高场强元素Nb、Ti的地球化学特征，显示其为地壳加厚的构造背景下，下地壳部分熔融的产物，其源区相当于含10%的石榴子石角闪岩相。结合区域资料，认为晚侏罗世特提斯构造域和太平洋构造域构造已经发生构造体制的转换，太平洋板块向西俯冲导致地壳加厚，加厚的基性下地壳物质发生熔融形成岩浆，并沿构造薄弱带上升，喷发形成该套粗面英安岩，可能代表了燕山运动B幕的岩浆事件。综合研究认为，华阳村组粗面英安岩与调查区内多金属成矿关系作用不大，由于形成了特殊的具有埃达克岩性质的岩石，势必引起下地壳的折沉作用，随着拆沉作用的持续进行，地壳减薄导致周围软流圈地幔上涌，含有Mo、Cu等成矿元素的岩浆沿着构造薄弱地带侵入就位，并在上升过程萃取了围岩中的Pb、Zn、Ag、Au等成矿元素，形成调查区内蟒岭含矿斑岩体、蟒岭西侧含矿小斑岩体以及同期的黄家沟-上铺子一带脉状铅锌银矿体。
Abstract:A series of trachydacite rocks are exposed in the Jurassic Huayangcun Formation in the southern part of the Mangling mining area of East Qinling Mountain. The zircon 206Pb/238U age is(150.92±0.70)Ma as shown by LA-ICP-MS technique, suggesting that they were formed in Late Jurassic. Geochemical characteristics show that the rocks are similar to the C-type of the Yanshanian period in eastern China in geochemical features, characterized by high SiO2(59.75%~60.97%), Al2O3(15.84%~16.01%), K2O(3.74%~3.89%), Sr(286×10-6~338×10-6), and Sr/Y(20.85~24.53), but low MgO(2.37%~2.66%), Yb(1.30×10-6~1.50×10-6) and Y(13.3×10-6~15.4×10-6), with obvious depletion of heavy rare-earth elements, distinct light and heavy rare earth elements (LREE/HREE=10.27~12.25),and weak positive Eu anomalies (1.21~1.37). Lithophile elements such as Rb, Ba, Sr, U and K are enriched, and high field strength elements Nb, Ti are depleted.The geochemical characteristics show that the rocks are products of partial melting of the lower crust thickening under the tectonic setting of the crust thickening, with the source area equivalent to 10% of the garnet amphibolite facies.According to the regional data, it is believed that the tectonics of the late Jurassic Tethys and the Pacific tectonics experienced variation, and the Pacific plate subducted to the west and resulted in the thickening of the crust, the thickening of the basic lower crust material and the formation of magma, the rise of the tectonic weak zone and the formation of the set of anganite, and this may represent the magmatic event of the B episode of the Yanshanian movement. The comprehensive study shows that the relationship between the coarse quartz dacite and the polymetallic mineralization in the investigation area is not significant, but, because of the formation of special rocks with adakite properties, the lower crust was dismantled, and the crust thinned and the asthenospheric mantle upwelled around it; magma containing Mo and Cu ore-forming elements invaded along weak tectonic zones, and there was extraction of Pb Zn, Ag and Au ore-forming elements in the surrounding rock during the rising process, thus forming ore-bearing porphyries in the Manling Mountains, the ore-bearing small porphyry in the west of the Manling Mountains and the vein-like Pb-Zn-Ag orebodies in the Huangjiagou-Shangpuzi belt in the same period.
keywords:geochemistry adakitic rock zircon U-Pb age metallogenic significance Mangling mining area East Qinling molybdenum metallogenic belt
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基金项目:本文得到陕西省公益性地勘专项项目"陕西秦岭造山带中生代构造体制及成矿作用研究（编号：20130301）"和新疆地勘基金项目"新疆和田县大红柳滩509道班西锂、铍多金属矿预查（编号：K17-3-XJ013）"的联合资助
引用文本：
郭岐明,赵江林,陈清敏,王强,高勇浩,杜彪,张栓厚.2019.东秦岭钼多金属成矿带蟒岭矿集区南部晚侏罗世埃达克岩的厘定及成矿意义[J].矿床地质,38(6):1297~1320GUO QiMing,ZHAO JiangLin,CHEN QingMin,WANG Qiang,GAO YongHao,DU Biao,ZHANG ShuanHou.2019.Identification of adakitic rock in southern Mangling mining area of East Qinling molybdenum polymetallic metallogenic belt and its metallogenic significance[J].Mineral Deposits38(6):1297~1320
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