Some metallogenic features of gold and copper deposits related to alkaline rocks and consequences for exploration
Some metallogenic features of gold and copper deposits related to alkaline rocks and consequences for exploration
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DOI：
10.1007/s00126-001-0227-6
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发表时间：
2002-02
影响因子：
4.8
通讯作者：
R. Sillitoe
中科院分区：
文献类型：
--
作者：
R. Sillitoe
与碱性岩有关的斑岩铜金、矽卡岩铜金、沉积物（卡林式）金、角砾岩筒、低硫化浅成热液金、与深成岩有关的（中生代或造山）金矿脉和火山成因块状硫化物矿床通常与钙碱性岩中的矿床大致相似。相比之下，斑岩金矿床仅限于碱性火成岩中心。碱性岩套在高硫化浅成热液型金矿床中明显缺乏，甚至在容纳它们的高级泥质岩盖中也是如此。这是令人惊讶的，因为所需的氧化硫物种似乎比钙碱性火成岩中心更丰富。交代碱性岩石对酸性流体的高效缓冲作用可能提供了一个可行的解释。所有类型的与侵入岩有关的锌矿床在碱性地区似乎也不太发育。与碱性岩石有关的几个金和铜矿床的特征，包括巨大的Porgera，Cripple Creek，Ladolam，Olympic Dam和Phalaborwa的例子，被认为与它们最密切相关的存款类型明显不同，使它们可以说是独特的。这些异常的矿化样式中的大多数可能是由于与矿石相关的碱性岩浆的极端多样性所导致的岩浆流体成分和释放特征的变化。在钙碱性地区开发的大多数类型的金和铜矿床也是碱性火成岩中心及其周围的勘探目标，尽管斑岩铜金矿和低硫化浅成热液金矿被认为具有最大的潜力。然而，也许更令人感兴趣的是，可能会遇到缺乏类似实例的非常规大型金铜矿。如果已经确定的异常矿床确实是独一无二的，那么专门为探测其他实例而设计的勘探就毫无意义。此外，勘探新的独特矿床是困难的，因为它们的定义地质参数是未知的。在会聚板块边界的钙碱性弧内或弧后的碱性岩可能提供最大的勘探潜力，尽管非造山陆内伸展环境不应被忽视。
Porphyry copper-gold, skarn copper-gold, sediment-hosted (Carlin-style) gold, breccia pipe, low-sulphidation epithermal gold, pluton-related (mesothermal or orogenic) gold vein and volcanogenic massive sulphide deposits associated with alkaline rocks are commonly broadly similar to those hosted by their calc-alkaline counterparts. In contrast, porphyry molybdenum-gold deposits are confined to alkaline igneous centres. Alkaline suites are notably deficient in high-sulphidation epithermal gold deposits and even in the advanced argillic lithocaps which host them. This is surprising, given that the required oxidised sulphur species are seemingly more abundant than in calc-alkaline igneous centres. Highly efficient buffering of acidic fluid by metasomatised alkaline rocks may offer a viable explanation. All types of intrusion-related zinc deposits also appear to be poorly developed in alkaline provinces. The characteristics of several gold and copper deposits associated with alkaline rocks, including the giant Porgera, Cripple Creek, Ladolam, Olympic Dam and Phalaborwa examples, are judged to diverge appreciably from their most closely related deposit types, rendering them arguably unique. Most of these aberrant mineralisation styles may be due to variations in magmatic-fluid compositional and liberation characteristics consequent upon the extreme diversity of ore-related alkaline magmas. Most types of gold and copper deposits developed in calc-alkaline provinces also constitute exploration targets in and around alkaline igneous centres, although porphyry copper-gold and low-sulphidation epithermal gold deposits are considered to possess the greatest potential. Perhaps of even greater interest, however, is the possibility of encountering unconventional giant gold and copper deposits which lack closely analogous examples. If already-defined aberrant deposits are truly unique, then exploration designed specifically to detect additional examples is pointless. Furthermore, exploration for new unique deposits is difficult because their defining geological parameters are unknown. Alkaline rocks within or behind calc-alkaline arcs at convergent plate boundaries probably offer the greatest exploration potential, although anorogenic intracontinental extensional settings should not be ignored.