加拿大拜韦尔特半岛金-铜矿集区成矿地质背景与矿床特征

Geological settings and characteristics of the Au-Cu metallogenic concentration area in the Baie Verte Peninsula,Newfoundland,Canada

拜韦尔特半岛矿产资源主要包括铜、金和石棉,区域地层和构造是控制矿床形成、发展和叠加改造的主要因素。这些矿产资源主要赋存在拜韦尔特海洋带达利吉带圣母玛利亚亚带的早奥陶世潜次火山岩中,包括起源于超俯冲作用带的蛇绿岩套和火山岩盖层。其蛇绿岩套超镁铁堆积岩的热液蚀变岩中产出石棉,火山成因的块状硫化物型(VMS型)铜±金矿产在基性和双峰式火山岩中,金矿产在基性和超基性的热液蚀变岩中。而蛇绿岩套火山岩盖层中则产出与条带状含铁建造(BIF)有关的后生金矿,石英脉型或相关的交代型矿床则大多赋存在蚀变和变形的基性岩中。拜韦尔特半岛的构造样式和几何结构非常复杂。

The Baie Verte Peninsula possesses rich mineral resources and has long been the focus of mining and exploration for copper, gold, asbestos and other deposits. The regional stratigraphy and structure are the main factors that control the formation, development and superposition of the deposits. These diverse mineral resources are mostly hosted in Lower Ordovician submarine volcanic rocks of the Baie Verte oceanic tract（BVOT） along the Notre Dame subzone of the Dunnage zone, which include ophiolite suites generated in a suprasubduction zone environment and their volcanic cover sequences. The ophiolite sequences host asbestos in hydrothermally-altered ultramafic cumulate sections, VMS-style（volcanogenic massive sulfide style） copper ± gold mineralization in mafic and bimodal mafic-felsic volcanic sequences, and gold mineralization in hydrothermally altered mafic and ultramafic rocks. In contrast, the volcanic cover sequences of the ophiolites host epigenetic gold deposits associated with banded iron formation, whereas quartz vein type or related replacement deposits are mostly hosted in altered and deformed mafic rocks. The structural style and geometry across the peninsula are very complicated. In the east, the Betts Cove Complex is folded into a relatively simple, large-scale, doubly plunging NE-trending syncline, whereas in the west（along the Baie Verte line）, similar ophiolite sequences and cover rocks are complexly folded and segmented by multiple generations of tightly spaced, NE-striking faults and shear zones.