华北克拉通破坏成矿响应的集成研究

Significant advance has been made in our understanding of late Mesozoic gold mineralization over the North China craton after extensive studies by domestic and overseas researchers. In the past decade, massive data and numerous papers have been accumulated, but little has been done in data integration, leaving metallogenic information of various data largely unexplored. In addition, comparative studies have been rarely conducted for gold deposits from distinct districts and, particulalrly, there is a lack of multi-disciplinary studies aiming to provide tight constraints on the genetic link between the craton-wide gold metallogeny and decratonization processes. Lastly, how the extent, styles, and evolution of gold mineralization has responded to the destruction of modification of the world's cratons remains poorly understood due to a lack of global perspective. The proposed research aims at the overall objectives of the big research plan of “Decratonization of the North China Craton” and make a comprehensive review and summary of the research finding on decrationization and its related gold deposits. Focusing on the key scientific question “genetic link between decrationization and metallogeny”, we will use multidisciplinary methods to figure out the deep processes of decratonization, particularly the connection between magmatism in the deep crust and formation of mineral deposits. The project would yield results that advance our understanding in the possible links of subduction of oceanic crust, decrationization, mantle-derived magmatism and gold mineralization. In order to further understand decratonization and its effect on ore formation, a comparative study will be carried out between gold mineralization in North China craton and other Precambrian cratonic blocks elsewhere that have partly lost their lithospheric roots . On the basis of data integration and regional and global comparative studies, we will plan to carry out a multi-disciplinary study on metallogenesis, key ore-controlling factors, localization of deep-seated orebodies in the Xiaoqinling district. We then finally make a scientific evaluation on the mineralization potential of deep part of known deposits and prediction of favorable sites for ore prospecting.

国内外学者对华北克拉通金矿床开展了大量深入研究，积累了丰富资料，取得了系列重要进展。但对已有成果的总结、对比和融合还不够，对华北克拉通破坏与金矿床的成因联系仍缺乏多学科的综合分析与集成，区域与全球对比研究亟需加强。本项目围绕《华北克拉通破坏》重大研究计划的总体目标，全面总结和集成克拉通破坏与成矿作用研究的系列成果，深入分析华北克拉通金矿床成因机制尚未解决的关键问题和争论的焦点，针对“华北克拉通破坏与矿产资源聚集的关系”这一核心科学问题进一步开展多学科交叉研究，揭示华北克拉通破坏深部过程尤其是深部岩浆活动与成矿的关系，进一步提升对大洋板块俯冲、克拉通岩石圈破坏、壳幔岩浆活动与金成矿作用成因联系的理论认识。开展全球对比，深化对克拉通破坏成矿效应的理解。基于上述成果集成，开展小秦岭矿集区金矿床深部成矿规律、关键控矿因素、矿体定位规律的多学科联合攻关，科学评价深部成矿潜力和预测找矿有利空间。

围绕“华北克拉通破坏与矿产资源聚集的关系”这一核心科学问题，系统总结与综合分析华北克拉通破坏背景下金成矿作用研究取得的重要进展，并重点开展了华北南缘中生代金矿床的成矿规律总结，选择小秦岭地区东桐峪金矿床开展了深部成矿和找矿潜力评价，揭示成矿作用条件的垂向变化，进一步总结和完善中生代金成矿作用与华北克拉通破坏之间的联系。通过项目的实施，确证了华北克拉通南缘存在晚三叠世钼矿化和早白垩世金矿化两期独立成矿事件，分别与秦岭造山带造山后伸展与华北克拉通岩石圈破坏的岩浆活动有关，对正确理解小秦岭的岩浆演化和成矿作用具有重要的指示意义。通过对不同地质体和不同成因黄铁矿的金含量及S-Pb原位同位素组成分析结果显示，以太华群为代表的古老变质岩和起源于古老变质岩部分熔融的花岗岩类侵入岩无法提供大规模成矿作用所需的金，而典型金矿床中矿石矿物黄铁矿微量元素和多种同位素组成显示金可能具有幔源岩浆来源的特征。通过对小秦岭地区成矿规律和矿体定位规律的研究，对东桐峪金矿床Ⅴ号勘探线实施深部钻孔验证，在地表之下约1600m揭露到一层厚度约1.6m、平均品位2.77g/t 的石英脉型金矿体，结合矿体原生晕的研究，表明小秦岭的深部仍存在工业意义的金矿化，但成矿规模比上部浅部矿体急剧弱化。同时开展了小秦岭与胶东矿集区深部强度差异的对比研究，认为缺乏深大的成矿期区域断裂和显著的幔源岩浆活动，可能是小秦岭地区成矿强度较弱的一个重要因素。通过区域成矿规律总结，提出华北南缘早白垩世金矿床、斑岩型钼矿床、脉状银-铅-锌矿床很可能是一个克拉通破坏背景下巨型区域岩浆-热液的成矿体系，其成矿作用一直影响到克拉通周缘的武当-桐柏-大别成矿带，两地的成矿作用具有统一的成矿动力学背景。通过克拉通破坏的全球对比，认为华北中生代大规模金矿床形成作用形成于古太平洋俯冲板块早白垩世的后撤作用，形成交代的富集岩石圈地幔可能是形成克拉通破坏背景下大规模金矿化的先决条件。