赣东北塔前-赋春推覆构造及其对超大型钨铜成矿作用的控制

The Mesozoic nappe tectonics are developed in the Taqian-Fuchun area, northeast Jiangxi Province, in which a lot of deposits (spots) with different types and scales, typified by the Zhuxi super-large W-Cu deposit, are widely distributed. In recent years, studies of the ore-forming mechanism for the large-scale W-Cu mineralization emphasized the effect of magma and fluid, while the research of relationship between the nappe tectonics supporting the main regional geological regime and metallogeny was paid less attention. Coexistence of the large-scale tectonics and super-large deposits in this area makes it an ideal place to understand the Mesozoic large-scale tectonic-metallogenic thermal events in eastern China. Based on the previous studies of nappe tectonic controlling on metallogeny, by means of theories and methods of deformation and mechanics analysis, thermochronology and numerical simulation, the applicant focuses on the main line of forming evolution of nappe tectonics and metallogenic structural plane and ore controlling mechanism, analyzing the constrains of the nappe tectonic geometry and deformation combination on metallogenic elements. Moreover, this project plans to identify the time-space evolutionary relationship between integral-local stress field together with thermal fluid-driven and the metallogenic structural planes in different stages of nappe tectonic development. Finally, we will carry out numerical simulation and comprehensive interpretation based on the stress-temperature-fluid coupling. This study is of great significance in enriching the theory research of ore-controlling tectonics especially in the superimposed area of deformation and magmatism in the southeast China, deepening recognition of the relationship between large-scale tectonics and super-large mineralization, and developing ore structural controlling quantitative simulation and ore positioning prediction.

赣东北塔前-赋春一带中生代推覆构造发育，并广泛分布以朱溪超大型钨铜矿为代表的不同类型及规模的矿床(点)。近年来对该区大规模钨铜矿床成因机制的研究主要强调岩浆与流体的作用，而对支撑该区主体格局的推覆构造与成矿关系的研究相对欠缺。大型构造与超大型矿床共存使该区成为认识中国东部中生代大规模构造—成矿热事件的理想场所。申请者在以往推覆构造控矿研究积累的基础上，结合前人认识，拟以推覆构造与成矿结构面成生演化及控矿机理为主线，利用变形力学解析、矿床学、热年代学及数值模拟理论方法，查明推覆构造几何结构及变形组合对成矿要素的约束；明确推覆构造不同阶段整体和局部应力场及热流体驱动与成矿结构面的时空关系；开展基于应力—温度—流体耦合的数值模拟及综合解释。该项研究对于丰富中国东南部变形与岩浆叠加复合区控矿构造理论，深化大型构造与大规模成矿的认识，拓展构造控矿定量模拟研究以及开展矿床定位预测具有十分重要的意义。

通过构造解析，结合同位素年代学研究表明，塔前—赋春构造带经历了NW-SE挤压作用（D1：248-226Ma）、NW-SE向推覆构造变形（D2：170-160Ma），挤压向伸展转换过渡（D3：160-61 Ma）和盆地边缘推覆构造变形（D4：61-40Ma）。提出塔前-赋春构造带NW向SE方向逆冲的叠瓦式构造样式及褶-断-冲的推覆构造发育模式。砂箱模拟实验表明基底深部存在拆离滑脱断层，推覆构造属于板内形成的具有基底拆离滑脱层的基底卷入型薄皮构造。明确了朱溪矿床镁矽卡岩、钙矽卡岩和Sch-Qtz-Ms脉型等三种类型的矿体是多期岩浆热液流体与不同围岩相互作用的结果。成矿流体最初来源于花岗岩浆，后与富含还原性物质的大气降水混合。流体不混溶、沸腾和混合的多次循环是W和/或Cu析出的机制。W的主要输运剂是还原性烷烃和氟化物、碳酸盐和磷酸盐配合物。控矿构造解析厘定出5种具不同力学性质的控矿构造类型，揭示出挤压向伸展转换时期的应力与流体共同作用的断层阀行为及水压致裂控制了朱溪W-Cu成矿作用。矿化发生在断层阀模型的流体压力骤降和流体沸腾阶段。通过建立热—应力耦合模型，开展数值模拟。结果表明最大主应力、最大剪应力、Mises等效应力和应变能等分布图中高值区与矿区内主要的控矿裂隙及主要矿体分布部位相吻合，证明区域伸展作用及岩浆热液共同作用控制了朱溪矿床的成矿空间。项目还将朱溪矿床所在的成矿区与华南重要成矿区带构造变形及构造控矿特征进行了对比。结合项目研究，共发表论文16篇，包括SCI论文8篇，培养博士后1名，硕士生3名，参加国际学术会议1次，国内学术会议4次。项目成果将为深化重要成矿区带构造变形及其控矿机理研究，以及开展朱溪超大型矿床深部及外围找矿提供理论依据。