The submarine tectono-magmatic framework of Cu-Au endowment in the Tabar-to-Feni island chain, PNG
The submarine tectono-magmatic framework of Cu-Au endowment in the Tabar-to-Feni island chain, PNG
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DOI：
10.1016/j.oregeorev.2020.103491
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发表时间：
2020-06
影响因子：
3.3
通讯作者：
P. Brandl;M. Hannington;J. Geersen;S. Petersen;H. Gennerich
中科院分区：
文献类型：
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作者：
P. Brandl;M. Hannington;J. Geersen;S. Petersen;H. Gennerich
西南太平洋地区，特别是巴布亚新几内亚，拥有丰富的矿产资源，包括世界上最年轻和最丰富的斑岩铜钼Au矿床。其中包括位于新爱尔兰东北部Tabar-Lihir-Tanga-Feni（TLTF）岛链中Lihir岛上的巨型斑岩-浅成热液型Ladolam Au存款。它位于前弧前盆地内，与大多数西南太平洋斑岩和浅成热液矿床非常不同。我们综合了船载多波束和地震研究、卫星重力测量、地球化学和地质年代学的已发表和以前未发表的数据，揭示了比目前仅从岛屿地质学了解的复杂得多的地壳结构和组成。我们表明，独特的区域Au禀赋是由多种多产成矿条件的排列所导致的：i）地幔源区的含水和富金属交代脉，ii）第二阶段，由于初始裂谷作用导致的低体积部分熔融，iii）由于交代脉中含水相的优先熔融导致熔体的高挥发分含量和氧逸度，iv）在Lihir的具体情况下，火山建筑物的屋顶被拆除，导致沸腾和快速金属沉积。这项研究表明，拉多拉姆存款的位置在利希尔控制的大型结构，可以追溯到海上，是持续的海底火山作用和浅成热液型Au矿化的网站。所观察到的结构框架是占主导地位的出现oftrans-lithospheric故障，提供了途径的熔体到海底，近地表结构集中的上升熔体和流体，和区域构造应力制度，稳定的条件在一个显着的时间和/或重复。海洋地震数据证实了TLTF岛链的复杂结构。每个岛群坐落在倾斜的地块上，这些地块形成地垒构造，由于区域NW-SE方向的伸展而形成半地堑。由于在翁东爪哇高原前缘从俯冲到碰撞的过渡，垂直于伸展的区域压缩继续存在。不同地壳块体之间的长期扭张运动控制了岩浆作用和成矿作用的位置和时间。在Lihir的位置和新爱尔兰的分裂在马努斯盆地的海底扩张的东北方向传播的火山活动之间的运动学联系被怀疑。通过结合陆上和海上地质，我们提出了新爱尔兰盆地的演化，岩浆沿着TLTF岛链，并最终矿石存款形成的新模式。这项研究表明，将近海地质和地球物理学整合到模型中的重要性，这些模型旨在解释经济矿床所在的边缘盆地的构造、岩浆和沉积演化。
The Southwest Pacific region, and Papua New Guinea in particular, is spectacularly endowed with mineral resources, including some of the youngest and richest porphyry Cu-Mo-Au deposits in the world. Among them is the giant porphyry-epithermal Ladolam Au deposit on Lihir Island in the Tabar-Lihir-Tanga-Feni (TLTF) island chain, northeast of New Ireland. Its setting within a former forearc basin is very different from most Southwest Pacific porphyry and epithermal deposits. Our synthesis of published and previously unreleased data from ship-based multibeam and seismic studies, satellite gravimetry, geochemistry and geochronology reveals a far more complex crustal structure and composition than is presently understood from the geology of the islands alone. We show that the unique regional Au endowment results from the alignment of various preconditions that are prolific to ore formation: i) hydrous and metal-rich metasomatic veins in the mantle source, ii) second-stage, low volume partial melting due to incipient rifting, iii) high volatile contents and oxygen fugacities of the melts due to preferential melting of hydrous phases in the metasomatic veins, and iv) in the specific case of Lihir, unroofing of the volcanic edifice that led to boiling and rapid metal deposition. This study shows that the location of the Ladolam deposit on Lihir is controlled by large-scale structures that can be traced offshore and are the site of continuing submarine volcanism and epithermal-style Au mineralization. The observed structural framework is dominated by the emergence oftrans-lithospheric faults that provided pathways for the melts to the seafloor, near-surface structural focusing of the ascending melts and fluids, and a regional tectonic stress regime that stabilized the conditions over a significant period of time and/or repeatedly. Marine seismic data confirms the complex structure of the TLTF island chain. Each island group sits on tilted blocks that form horst structures separated by half grabens developed due to regional NW-SE-directed extension. Regional compression perpendicular to the extension continues as a result of the transition from subduction to collision at the leading edge of the Ontong Java Plateau. The protracted, transtensional motion between distinct crustal blocks controls the location and timing of magmatism and mineralization. A kinematic link between volcanism at the location of Lihir and the splitting of New Ireland by NE-directed propagation of seafloor spreading in the Manus Basin is suspected. By combining onshore and offshore geology, we propose a new model of the evolution of the New Ireland Basin, magmatism along the TLTF island chain and ultimately ore deposit formation. This study demonstrates the importance of integrating offshore geology and geophysics into models that aim to explain the structural, magmatic, and sedimentary evolution of marginal basins that are host to economic mineral deposits.