A rare Phanerozoic amphibolite-hosted gold deposit at Danba, Yangtze Craton, China: significance to fluid and metal sources for orogenic gold systems

Hesen Zhao, Qingfei Wang, David I. Groves, Jun Deng

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

The Danba gold deposit is located in a poorly-documented gold province on the north-western margin of the Yangtze Craton. It is sited in Devonian sequences in a high-grade metamorphic terrane that includes an extensional metamorphic core complex. Around the deposit, peak metamorphic conditions of 6 +/- 0.5kbar and 650 +/- 50 degrees C at ca. 193Ma were followed by retrograde sillimanite-grade conditions of 4.5 +/- 0.5kbar and 550 +/- 50 degrees C. The deposit is hosted in a broadly strata-bound ductile-brittle shear zone with high-T proximal alteration assemblages of biotite-amphibole-plagioclase and ore assemblages dominated by pyrrhotite, but with a strong association between gold and bismuth tellurides. Alteration mineral thermobarometers, together with heating/freezing studies of low-salinity H2O-CO2-CH4 fluid inclusions, indicate P-T conditions of early ore deposition of approximately 4-5kbar and 500-650 degrees C at around 185 +/- 9Ma indicated by Re-Os geochronology on ore-related molybdenite. In conjunction, all data demonstrate that Danba represents a Lower Jurassic hypozonal orogenic gold deposit that formed during post-peak metamorphic retrogression. The primary high P-T nature of the deposit, combined with its late-metamorphic timing, negate that the ore fluid was sourced via devolatilization of the hosting supracrustal sequences. A deep externally-derived ore-fluid source is required. The most likely source is the K-H2O-CO2 and ore-metal fertilized lithospheric mantle that was metasomatized during Neoproterozoic subduction. It is proposed that transition from lithospheric transpression to extension in the Jurassic triggered the devolatilization of this metasomatized lithosphere to cause the formation of this rare Phanerozoic amphibolite-hosted gold deposit at Danba.

Original languageEnglish
Pages (from-to)133-152
Number of pages20
JournalMineralium Deposita
Volume54
Issue number1
DOIs
Publication statusPublished - Jan 2019

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