冀东下营坊地区晚古生代富碱侵入岩锆石U-Pb年代学、岩石地球化学及其地质意义

发布时间：2019-06-19 06:58

【摘要】：富碱侵入岩具有重要的地质和矿产意义,倍受学者关注。冀东地区晚古生代钙碱性岩浆岩十分发育,而碱性岩少见,笔者首次在冀东下营坊地区识别出一批与金(铜铅锌银)多金属矿化有关的晚古生代中晚期的富碱侵入岩体。通过锆石LA-ICP-MS U-Pb测年,获得下营坊地区三处富碱侵入岩的侵位年龄分别为300.0±1.5Ma、299.3±2.1Ma、300.0±2.0Ma,侵位时间显示这些岩浆岩均为晚石炭世末—早二叠世的产物。岩石地球化学特征显示富碱(K2O+Na2O8%),稀土元素含量较高,并强烈富集轻稀土,指示其具有富碱侵入岩的基本特征。下营坊富碱侵入岩富集大离子亲石元素,高La/Yb比,较高的La/Sm比值且变化范围大(5),低Y,Eu异常不明显等特点,表明其源区可能与富集地幔有关,并可能受到俯冲板片脱水所释放流(熔)体的影响,在岩浆的侵位过程中可能受到地壳物质的混染。由成岩时代结合区域构造演化历史推断,该地区富碱侵入岩很可能与古生代期间古亚洲洋板块向华北板块俯冲有关,并形成于由俯冲板块后撤的伸展环境。
[Abstract]:Alkali-rich intrusive rocks have important geological and mineral significance and have attracted the attention of scholars. The late Paleozoic calc-alkaline magmatic rocks in eastern Hebei are very developed, but the alkaline rocks are rare. For the first time, a number of late Paleozoic alkali-rich intrusive rocks related to gold (copper, lead, zinc and silver) polymetallic mineralization were identified in Xiayingfang area, eastern Hebei Province. By zircon LA-ICP-MS U-Pb dating, the emplacement ages of three alkali-rich intrusive rocks in Xiayingfang area are 300.0 卤1.5 Ma, 299.3 卤2.1 Ma and 300.0 卤2.0 Ma, respectively. the emplacement time shows that these magmatic rocks are the products of the late Permian and late Permian. The geochemical characteristics of rocks show that K _ 2O Na2O8% is rich in alkali, the content of rare earth elements is high, and it is strongly enriched in light rare earth elements, indicating that it has the basic characteristics of alkali-rich intrusive rocks. The alkali-rich intrusive rocks in Xiayingfang are rich in large ion lithophile elements, high La/Yb ratio, high La/Sm ratio and wide range of variation (5), low Y, EU anomaly is not obvious and other characteristics, indicating that the source region may be related to the enrichment of the mantle, and may be affected by the flow (melting) released by the dehydration of the subduction plate, and may be contaminated by crustal material during the emplacement of magma. From the diagenetic age combined with the regional tectonic evolution history, it is inferred that the alkali-rich intrusive rocks in this area are likely to be related to the subduction of the paleo-Asian ocean plate to the North China plate during the Paleoera, and formed in the extensional environment in which the subduction plate retreated.
【作者单位】：北京矿产地质研究院;有色金属矿产地质调查中心;
【基金】：青年科学基金项目(编号41602098) 国家自然科学基金项目(编号41030424) 国家“973”计划项目(编号2014CB440803) 中国地质调查局项目(编号12120113059800、DD20160072)联合资助的成果
【分类号】：P588.1;P597.3

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