Hydrothermal mobilisation of Au and other metals in supra-subduction oceanic crust: Insights from the Troodos ophiolite

作者: C.G.C. Patten , I.K. Pitcairn , D.A.H. Teagle

DOI: 10.1016/J.OREGEOREV.2017.02.019

关键词:

摘要: The Troodos ophiolite is an ideal location to investigate the relationships between mobilisation of metals by hydrothermal fluids from lower oceanic crust and formation volcanogenic massive sulphide (VMS) deposits. hosts classic “Cyprus-type” Cu-rich VMS deposits as well abundant zones epidosite alteration in sheeted dyke section that are significantly depleted base including Cu Zn, considered be source enriched overlying Previous research indicates irregularly Au related elements As, Sb, Se, but behaviour these during hitherto has been poorly investigated. Low detection limit whole rock analyses fresh glass samples reveal primitive a similar metal content distribution modern-day arc-related environments such Manus Basin. Compared mid-oceanic ridge basalt (MORB), Sb Pb most likely due addition subducting slab crustal formation. During early stages magmatic differentiation (9–3.5 wt% MgO) Au, Cu, Zn behave incompatible sulphide-undersaturated nature melt. onset magnetite crystallisation, however, at ∼3.5 MgO leads segregation depletion strongly chalcophile (Au, Se) continued (<3.5 whereas (As, Pb) remain incompatible. These differences can account for Cu-rich, Zn-Pb-poor Cyprus-type area rocks show high fertility compared Pb. Mobilisation more extensive than observed hydrothermally altered MORB. Mass balance calculations (−88 ± 16%), As (−89 23%), (−60 12%), Se (−91 20%), (−84 18%), (−63 9%) 8%). Background diabase outside shows depletions which suggests areas not restricted extended section. masses mobilised 10.9 km3, (composed 5 km3 zone 5.9 background diabase) Solea graben 47 t 21 kt 1200 3100 2.4 Mt 1.8 27 Comparison quantities dike with those hosted trapping efficiencies ranging 4 37% indicating lost other processes.

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