中下扬子及其毗邻地区含铜中酸性侵入岩的地球化学研究

The major copper-related magmatic rocks in the the Middle and Lower Yangtze and its adjacent regions are mainly adakitic intermediate-acid intrusive rocks that has important indication significance in the tectonics and ore deposit geology. Applicant has noted that the copper-related magmatism and mineralization exhibit younging formation ages with decreasing copper reserves from the southwest to the northeast. However, the whole-rock geochemical results give wide-ranging results at present and need to be higher still. .Studies in recent years have shown that accessory minerals can record the initial magmas or fluids directly and can give additional information on petrogenesis. It's known best for zircon which has been used successfully for tracing magma sources and estimating the oxygen fugacity. Recent studies have suggest that titanite and apatite might be sensitive to mixing processes, oxygen fugacity, fluid circulation or P-T conditions and received more and more attention. Therefore, a comparative study of the copper-bearing adakitic intermediate-acid intrusive rocks is proposed on this project between of the Middle and Lower Yangtze region and its adjacent Dexing region. Titanite, apatite and zircon are combined to analysis the formation mechanism and nature of the copper-related magmatism and mineralization and further discuss the petrogenesis of the regularly copper-related magmatism and mineralization.

中下扬子及其毗邻地区与铜成矿有关的岩浆岩主要为具有埃达克岩特征的中酸性侵入岩，有着重要的构造学和矿床学指示意义。申请人注意到铜成岩成矿作用存在自西南向东北方向时代逐渐变年轻，铜矿储量逐渐减弱的规律性演化现象。目前全岩的地球化学结果变化范围很大，需要进一步的提高。.近年来的研究表明副矿物是初始岩浆或流体的直接记录，可以提供更进一步的岩石成因方面的见解。其中尤以锆石最为出名，已被成功的用来示踪岩浆源区和估算氧逸度。榍石和磷灰石对混合过程，氧逸度，流体循环或P-T条件等很敏感，受到越来越多的关注。因此，本项目拟通过中下扬子地区和与其毗邻的德兴地区的含铜中酸性侵入岩进行对比研究，将榍石、磷灰石和锆石结合起来讨论铜成岩成矿作用的形成机制和本质，进一步分析中下扬子及其毗邻地区铜成岩成矿作用规律性变化的成因。

晚中生代时期发育巨量的岩浆岩与成矿，对这些不同成矿属性岩浆岩进行研究对于我们理解构造学和矿床学具有指示意义。本项目主要研究了中下扬子以及秦岭造山带内成矿相关的岩浆岩的主微量元素，Sr-Nd-Pb-Hf同位素及部分副矿物成分来探寻岩浆与成矿的成因。我们发现中下扬子地区铜、铁成矿相关岩浆岩虽然具有类似的Sr-Nd-Pb-Hf同位素组成，但存在明显的差异性：铜成矿相关岩浆岩具有中等的SiO2，高K2O和镁数，高氧逸度，可能与大洋板块俯冲环境有关，铁成矿相关岩浆岩具有高的SiO2和K2O，低镁数，低氧逸度，可能与大洋板块撤离后陆内拉升环境有关。同时我们发现秦岭造山带内钼成矿相关岩浆岩具有非常大变化的Nd同位素并且与SiO2显示不协调的正相关演化关系，这可能与造山过程中俯冲大陆地壳物质加入有关。因此，晚中生代时期巨量不同成矿相关岩浆岩具有明显的差别，有待进一步的研究工作。