Unraveling the origin of the Andean IOCG clan: A Re-Os isotope approach

Abstract

'Unraveling the origin of the Andean IOCG clan : a Re-Os isotope approach.', Ore geology reviews., 81 (Part 1). pp. 62-78. Further information on publisher's website: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. A C C E P T E D M A N U S C R I P T Chilean IOCGs is the result of different events with metals derived from diverse sources i.e., the magmatic-hydrothermal system and basement/host rocks. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPTRhenium and Os concentrations for the various studied deposits vary over a wide range of values at the ppb and ppt level, respectively, with many sulfides and magnetite bearing appreciable no common Os. The Re and Os contents in sulfides (pyrite, IOCGs in China and Australia argue for the involvement of a much more radiogenic crustal source possibly related to non-magmatic oxidized saline brines that leached basement rocks. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPTWe conclude that Andean IOCG (and IOA) deposits in northern Chile were formed mainly by magmatic-hydrothermal processes related to the formation and emplacement of plutonic rocks with moderate contribution from leaching of basement and/or volcanic host rocks. Surface or basin-derived brines as well as sediments appear to play only a minor role in the formation of the Chilean IOCG clan.

Kiruna-Type Iron Oxide-Apatite (IOA) and Iron Oxide Copper-Gold (IOCG) Deposits Form by a Combination of Igneous and Magmatic-Hydrothermal Processes: Evidence from the Chilean Iron Belt

“…Secondary ion mass spectrometry (SIMS) was used to measure the abundances of Cu, As, Se, Ag, Sb, Te, and Au in pyrite . Negative-thermal ionization mass spectrometry (N-TIMS) was used to measure the abundances of 187 Re, 187 Os, and 188 Os in magnetite and pyrite mineral separates (Barra et al, 2017). Transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) were used to analyze nano-and micron-scale inclusions in late-stage hydrothermal, disseminated magnetite grains .…”

“…The belt contains Kiruna-type IOA, IOCG, and stratabound Cu(-Ag) deposits, which are commonly referred to as Manto-type Cu(-Ag) deposits ( Fig. 1; Barra et al, 2017). Mineralization occurred during the Cretaceous, with ages that range from about 130 to 90 Ma (Oyarzún et al, 2003;Barra et al, 2017).…”

“…1; Barra et al, 2017). Mineralization occurred during the Cretaceous, with ages that range from about 130 to 90 Ma (Oyarzún et al, 2003;Barra et al, 2017). The ore deposits in the belt are spatially associated with the Atacama fault system, a nearly 1,000-km-long, N-S-trending, trench-parallel system that resulted from the synchronous opening of the South Atlantic Ocean basin and oblique subduction beneath western South America (Uyeda and Kanamori, 1979;Scheuber and Andriessen, 1990;Brown et al, 1993).…”

“…2;Espinoza et al, 1996;Sillitoe, 2003;Williams et al, 2005). This observation of a structurally controlled, vertical continuum, has led many to hypothesize that the two deposit types are part of a single oreforming system (Sillitoe, 2003;Williams et al, 2005;Barra et al, 2017). Supporting this hypothesis are temperatures of mineralization obtained from fluid inclusion microthermometry and mineral-mineral stable isotope thermometry that indicate that Kiruna-type mineralization formed at higher temperatures relative to IOCG mineralization (Williams et al, 2005;Barton, 2014).…”

“…Host rocks for IOCG and IOA deposits range from felsic to mafic igneous rocks, clastic to chemical sedimentary rocks, and their metamorphic equivalents. Modified from Barra et al (2017). Experimental data that constrain the partitioning of oxygen isotopes between immiscible Fe-and Si-rich melts also disallow the liquid immiscibility model to explain Kiruna-type IOA deposits. Lester al.…”