| 北京怀柔云蒙山地区花岗岩风化过程的地球化学基因 |
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| 引用本文： | 王旭阳,姚宁,龚庆杰,晁岳德,彭程,吴媛.北京怀柔云蒙山地区花岗岩风化过程的地球化学基因[J].地学前缘,2021,28(1):363-374. |
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| 作者姓名： | 王旭阳 姚宁 龚庆杰 晁岳德 彭程 吴媛 |
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| 作者单位： | 中国地质大学(北京)地球科学与资源学院,北京100083;中国地质大学(北京)地球科学与资源学院,北京100083;中国地质大学(北京)地球科学与资源学院,北京100083;中国地质大学(北京)地球科学与资源学院,北京100083;中国地质大学(北京)地球科学与资源学院,北京100083;中国地质大学(北京)地球科学与资源学院,北京100083 |
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| 基金项目： | 国家重点研发计划重点项目(2017YFC0803807);中央高校基本科研业务费专项(2652017221) |
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| 摘 要： | 地球化学基因是近两年提出的一种新的地球化学示踪技术,本文选择北京怀柔云蒙山地区两个邻近的花岗岩风化剖面(编号为B和C)来分析岩性地球化学基因和金矿化地球化学基因的属性特征。剖面B样品的化学蚀变指数CIA变化为51.3~58.9,WIG的范围为89.4~68.6,属于初始风化程度;剖面C样品的CIA变化为52.4~78.4,WIG的范围为84.8~25.3,属于中等风化程度。这种邻近剖面风化程度的明显差异表明微环境对岩石风化产物的影响是显著的。相对于剖面底部新鲜花岗岩而言,岩性地球化学基因相似度在剖面B和C中的范围分别为85%~100%和90%~100%,金矿化地球化学基因相似度范围分别为85%~100%和80%~100%。当相对于剖面顶部土壤样品时,岩性地球化学基因相似度在剖面B和C中的范围分别为80%~100%和90%~100%,金矿化地球化学基因相似度范围分别为85%~100%和80%~100%。依据≥80%的基因相似度标准(区分基因是否相似),尽管两个剖面在风化程度上存在明显差异,但岩性地球化学基因和金矿化地球化学基因在两个剖面内部均表现出良好的遗传性和继承性,且在两个剖面之间体现出同源风化产物之间具有良好的相似性。相对于理想金矿石(其金矿化基因为12020202020)而言,金矿化相似度在剖面B和C中的范围分别为25%~50%和30%~50%。依据≥40%的金矿化相似度(即样品与理想金矿石的金矿化相似度)作为存在金矿化异常的标准,在两个剖面中均可识别出厚度约1 m左右的矿化异常层位。因此,金矿化基因除了具有地球化学基因的属性(遗传性、继承性、相似性)外,其金矿化相似度(即相对于理想金矿石的相似度)也有可能作为金矿勘查中的一个地球化学综合指标。
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| 关 键 词： | 花岗岩风化剖面 岩性地球化学基因 金矿化地球化学基因 风化指数 微环境 |
| 收稿时间： | 2019-12-05 |
Geochemical genes related to granite weathering in the Yunmengshan area of Beijing,China |
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| WANG Xuyang,YAO Ning,GONG Qingjie,CHAO Yuede,PENG Cheng,WU Yuan.Geochemical genes related to granite weathering in the Yunmengshan area of Beijing,China[J].Earth Science Frontiers,2021,28(1):363-374. |
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| Authors: | WANG Xuyang YAO Ning GONG Qingjie CHAO Yuede PENG Cheng WU Yuan |
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| Institution: | School of Earth Sciences and Resources, China University of Geosciences(Beijing), Beijing 100083, China |
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| Abstract: | The geochemical gene technique is a new geochemical tracing technique formally proposed over the past two years. In this investigation, samples from two adjacent weathering profiles (B and C) developed in granite in the Yunmengshan area of Beijing, China were collected to test two geochemical genes named lithogene and gold metallogene. In samples from profile B, the chemical index of alteration (CIA) varied between 51.3-58.9, and the weathering index of granite (WIG) varied between 68.6-89.4, indicating incipient weathering in this profile; while in samples from profile C, CIA varied between 52.4-78.4, and WIG between 25.3-84.8, indicating intermediate weathering in profile C. The noticeable difference of weathering degrees between the two adjacent profiles indicates that different micro-environment may result in significantly different weathering products in the same granite. The lithogene similarity between samples and fresh granite varied from 85% to 100% in profile B and 90% to 100% in profile C, while the gold metallogene similarity between the two varied from 85% to 100% in profile B and 80% to 100% in profile C. With respect to top soil, the similarity of lithogenes varied from 80% to 100% in profile B and 90% to 100% in profile C, and the gold metallogene similarity varied from 85% to 100% in profile B and 80% to 100% in profile C. According to the criterion that gene similarity above 80% indicates similar genes, the lithogene and gold metallogene illustrate not only good heredity and inheritance in each profile but also high similarity between the two profiles. Besides, with respect to the ideal gold ore (gold metallogene 12020202020), the similarity of gold metallogenes varied from 25% to 50% in profile B and 30% to 50% in profile C. According to the criterion that mineralization can be recognized when the gold metallogene similarity reaches 40%, one mineralization layer of ca. 1 m thickness can be recognized in each profile. Thus, the gold metallogene may also be used as an integrated geochemical indicator in gold exploration. |
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| Keywords: | weathering profiles of granite geochemical lithogene geochemical gold metallogene weathering indices micro-environment |
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