论扬子地块西缘元古宙铁氧化物铜金型矿床与大地构造演化

Geotectonic Evolution and the Proterozoic Iron Oxide Copper-Gold Deposits on the Western Margin of the Yangtze Massif

探讨和总结了扬子地块西缘大地构造演化、元古宙重大构造-岩浆事件与铁氧化物铜金型（IOCG）矿床关系,以促进对深部隐伏 IOCG 矿床勘查和新技术研发。在新太古界-古元古界小溜口岩组顶部和不整合面之下,含矿层状-似层状碱性方解石钠长石岩中锆石SHRIMP U-Pb年龄为2520±14 Ma,这种似层状铜矿床和其上不整合面型Cu-Co-Au- Ag-REE-Fe矿体,以云南东川因民铁铜矿床深部小溜口岩组中铜矿床为代表。总体上, IOCG矿床与扬子地块大地构造演化之间关系为：（1）扬子地块于东川运动（中条运动/Hudsonian Orogeny,1800 Ma）形成了陆壳基底。在中元古代初期（1700±50 Ma）发生了地幔热物质上涌侵位的构造-岩浆事件,导致古扬子地块发生裂解并形成裂谷构造和大陆裂谷盆地。在近东西向大陆裂谷盆地发育初期,构造动力学特征为火山地堑式断陷成盆。在碱性铁钠质基性岩、铁钾质粗面岩和铁质辉绿辉长岩形成过程中,形成了第一期IOCG矿床成岩成矿高峰期（1650±50 Ma）,以云南大红山IOCG矿床为代表。（2）在裂谷盆地成熟发育期,构造动力学特征为裂陷沉降成盆。因民期和黑山期两次地幔热物质上涌侵位,导致了构造-岩浆-成岩成矿事件发生。在铁钠质基性火山岩、铁钾质粗面岩、水下火成碳酸岩、火山喷溢-火山热水喷流沉积相等形成过程中,形成了第二期IOCG矿床的成岩成矿高峰期（1500±50 Ma）,以云南迤纳厂IOCG矿床为代表。（3）在小黑箐运动/满银沟运动（格林威尔造山期,1000 Ma±）,扬子地块南缘形成了近南北向洋壳俯冲和陆缘侧向挤压收缩体制,碱性铁质辉长岩-辉绿岩体上涌侵位,伴随同构造期脆韧性剪切带形成和沉积盆地构造反转,形成区域性不整合面（小黑箐运动/满银沟运动）和后期沉积型-火山沉积型铁矿床,为IOCG矿床第三期成岩成矿高峰期（1000±100 Ma）。以白锡腊深部和新塘IOCG矿床为代表,形成IOCG矿床和IOCG矿床的叠加成岩成矿。（4）晋宁-澄江期为多重构造体制耦合与转换格局,扬子地块内部和陆缘具有造山带-沉积盆地-深部地幔柱上涌侵位,深部地幔柱上涌侵位形成的碱性铁质辉长岩具有OIB源区特征,形成了第四期IOCG矿床的成岩成矿高峰期（800±50 Ma）,以四川拉拉IOCG矿床受碱性铁质辉长岩侵位与叠加成岩成矿为代表。在澄江期“盆→山”耦合与转换, IOCG矿床和东川型铜矿中进一步发生了盆地流体叠加改造富集（810~700 Ma）。

In order to promote the exploration and develop new exploration techniques for IOCG deposits at depth, the relationships between the Proterozoic iron oxide copper gold （IOCG） deposits on the western margin of the Yangtze massif, and the Proterozoic major tectonic-magmatic events along with their tectonic evolution are discussed in this paper. There is an unconformity between the Yinmin Formation of the Middle Proterozoic Dongchuan Group and the Late Archean to the early Proterozoic Xiaoliukou Association. SHRIMP U-Pb dating of zircon from the layered-bedded albitite in the Archean to the early Proterozoic Xiaoliukou Association which hosts the Cu-Co-Au-Ag-REE-Fe orebodies yields an age of 2520±14 Ma. Nevertheless, issues such as the unconformity-type of the Cu-Co-Au-Ag-REE-Fe mineralization and formation mechanism of hydrothermal breccia in the Xiaoliukou Association in Yunnan province are still open to debate. The relationships between the Proterozoic IOCG deposits and major tectonic-magmatic events of the Yangtze massif are propsed as the followings. Firstly, after following the Dongchuan Orogenorogenic movementy （Hudsonian Orogeny, ca. 1800 Ma±）, the basement tectonic layer of the continental crust on the Yangtze massif could have been formed. However, Tectonictectonic-magmatic emplacement events of the mantle upwelling occurred in the early Mesoproterozoic age （1700±50 Ma）, resulted the Yangtze massif split and the formation of the rifted basin. Basin-tectonic dynamics for the east-west-trending rifted basin was characterized by the volcano-graben basin at the early stage of the continental rifted basin. The first peak of IOCG diagenesis-mineralization period （1650±50 Ma） took place during the emplacement of the alkaline Fe-Na-rich basic rocks, Fe-K-rich trachyte, the Fe-rich diabases and gabbros along with the contemporary eruptions of volcanic rock of similar compositions, as exampified by the Dahongshan IOCG deposit in Yunnan province, China. Secondly, the mature stage of the rifted basin occurred during the Heishan Period and developed of the Middle Proterozoic Dongchuan Group, during which the tectonic dynamics was characterristics werezed by of basin-rifting subsidence in the rifted basin of mature development period. The event of hot mantle upwelling and emplacement occurred, and resulted in the tectonic-magmatic events and mineralization in the Heishan Period. The second IOCG mineralization peak （1500±50 Ma） was associated with the emplacement of the alkaline Fe-Na-rich basic rocks, Fe-K-rich trachyte, and underwater igneous carbonatite were produced at the sea bed while a variety of as well as marine volcanic lithofacies, such as volcanic eruption facies and volcanic exhalatives sedimentary facies, developed atin the rifted basin. At the same time, the second diagenesis-mineralization peak （1500±50 Ma） for the IOCG deposits started,, and the Yinachang IOCG deposit as theis a representative of the Yinachang IOCG deposit in Yunnan province, China. Thirdly, when the Xiaoheiqing or the Manyingou Orogeny （1000±100 Ma, the Grenville Orogeny） in Yunnan and Sichuan provinces was onset, the nearly north-directed subduction of oceanic crust, i.e., continental margin lateral compressional and shrinkage on the southern margin of the Yangtze massif, was commenced at the beginning of the Grenville Orogeny. Actually, the Grenville Orogeny resulted in the tectonic inversion of the rifted basin. Simultaneously, a series of alkaline Ti-Fe-rich gabbro and diabase intrusions emplaced, and they were accompanied by syn-tectonic brittle-ductile shear zones. The Manyingou orogeny or the Xiaoheiqing orogeny （the Grenville Orogeny） was responsible for the formation of a regional angular unconformity and disconformity in Yunnan and Sichuan provinces. The third peak （1000±100 Ma） of the IOCG diagenesic-metallogenic period could have beenmay be closely related to the alkaline Ti-Fe-rich gabbro and diabase intrusions with syn-tectonic brittle-ductile shear zones. The Baixila and Xintang IOCG deposits in Yunnan province are the representatives of the IOCG deposits. However, these IOCG deposits are of the Ti-high series IOCG deposits, whereas diagenesis-mineralization of the pre-existing IOCG deposits were superimposed by the alkaline Ti-Fe-rich gabbro and diabase emplacement with syn-tectonic brittle-ductile shear zone. Finally, on the one hand, the interiors and margins of the Yangtze massif were typified by the pattern of multiple tectonic system coupling and transformation during the Jinning-Chengjiang movement, that is, conversion of orogenic belt and sedimentary basin with the deep mantle plume upwelling. Therefore, emplacement of alkaline Fe-rich mafic gabbro with OIB source characteristics, led to the formedation of in the fourth peak （800±50 Ma） of the IOCG deposits diagenesis and mineralization period with which is coincident with the peak of regional metamorphism. On the other hand, the IOCG deposits and the Dongchuan-type copper deposits were superposed by Cu-bearing quartz veins derived from basin-fluid, and further enriched by basin-to-mountain transformation and coupling during the Chengjiang movement.