Trace element geochemistry of sphalerite from polymetallic sulfide mineralization in Betul belt, Central Indian Tectonic Zone, India

Mishra, Bishnu1, Pati, Pitambar1, Dora, Muduru1

1Indian Institute Of Technology Roorkee, Roorkee, India

Sulfide mineralization in Betul belt (BB) in the central India tectonic zone (CITZ) is one of the critical zinc-enriched polymetallic sulfide mineralization in India. Stratiform ore bodies hosted within the volcano-sedimentary units were moderately conceptualized to be a volcanic-hosted massive sulfide (VHMS) type deposit by earlier workers. As it is not yet wholly realized whether the deposit is genetically less fertile or underexplored, uncertainty remains in its future course of exploration. In this study an effort has been made to provide insights into various genetic aspects of mineralization, including major elements content, the enrichment of trace elements, and consequently, their broad exploration significance. Therefore, sphalerite trace element geochemistry has been studied using electron probe microanalyzer (EPMA) to obtain total major elements and laser ablation inductively coupled mass spectroscopy (LA-ICP-MS) to measure trace elements concentration. The trace elements such as Pb, Mn, Co, Cu, Ga, Ge, Ag, Cd, In, Sn, Sb, Bi, along with Fe in bulk sphalerite specimens have been analyzed using LA-ICP-MS technique. Thereafter, the dataset has been investigated using a multivariate statistical procedure called principal component analysis (PCA). This study shows that sphalerite in the BB are relatively abundant in Fe content ranging from 4.58 wt% to 11.10 wt% with mean 7.54 wt%. Trace elements like Mn and In show comparatively high concentration with a mean value of 3533.31 ppm and 33.73 ppm respectively. On the other hand, Ga, Ge and Ag content are depleted in the sphalerite with a mean value of 0.58 ppm, 0.36 ppm and 0.90 ppm respectively. Subsequently, the ore-forming temperature is conservatively and separately estimated using the geothermometers devised by Kullerud, 1953 and Frenzel et al., 2016, which range from 3190C to 5560C and 374.100C to 402.250C respectively. This study suggests the sulfide mineralization in the BB is high temperature, magmatic-hydrothermal origin. The enrichment of elements is predominantly controlled by the ore-forming temperature and host lithology. We observed the effect of metamorphism and recrystallization of the BB sphalerite. We encouraged to target basement exposed areas for further exploration activities. Pre to syn mineralization deformation structures are considered to be useful to locate the mineralization. This study also significantly added the degree of confidence to the growing consensus and typified BB sulfide mineralization as a VHMS type of deposit.

Keywords: Sphalerite, LA-ICP-MS, trace element geochemistry, Sulfide Mineralization, VHMS, Betul Belt.


Biography

Bishnu Prasad Mishra completed his B.Sc. from Utkal University, Odisha in Geology, and M.Sc. from Indian Institute of Technology Roorkee, Roorkee. At present, he is pursuing a Ph.D. with MHRD Fellowship with the supervision of Dr. Pitambar Pati in the Department of Earth Sciences, IIT Roorkee.

Geochemical and mineralogical signatures of IOCG and affiliated copper deposits in the Mount Isa Province, Queensland, Australia

Lisitsin, Vladimir1, Dhnaram, Courteney1

1Geological Survey of Queensland, Brisbane, Australia

Geological Survey of Queensland (GSQ) has undertaken systematic geochemical and mineralogical characterisation of numerous Iron-oxide copper-gold (IOCG) and affiliated copper ± gold deposits in the Cloncurry district of the eastern Mount Isa Province. This work contributes to and expands a current collaborative project between GSQ and CSIRO, focusing on characterisation of key mineral systems and deposits in the region. The geochemical and mineralogical dataset is based on >1,000 of individual samples from multiple deposits, including Ernest Henry, E1, Great Australian, Mount Elliott – SWAN, Eloise, Little Eva, Blackard, Kalman, Osborne and Starra. Samples from each deposit were generally collected from multiple boreholes, at a spacing from 15 m to 50 m, to characterise the range from high-grade mineralisation to proximal alteration zones and further to relatively distal samples, hundreds of metres away from visible mineralisation. More extensive sampling and analytical work was undertaken around the Ernest Henry and Mount Elliott – SWAN deposits, aiming to better characterise geochemical and mineralogical zonation at a scale of hundreds to thousands of metres.

Major and trace element geochemistry (for up to 67 elements) was consistently characterised using a combination of digestion methods and analytical techniques. All samples were analysed using four-acid digestion and ICP-MS / OES (48 elements), with the majority also analysed by lithium metaborate fusion and ICP-MS / OES (31 elements, to ensure near-total digestion of Ba, REE, Sn, W, U), fire assay and ICP-MS (Au, Pt. Pd), Leco furnace (C, S), KOH fusion – ion chromatography (F) and Aqua regia – ICP-MS (Hg, Se, Te). Prior to geochemical sampling, drill core samples (and often – entire drill cores) were scanned using GSQ’s HyLogger-3 to characterise spectral mineralogy.

Exploratory statistical data analysis (principal component and clustering analyses) highlight a multi-element geochemical signature common for almost all of the sampled copper-gold deposits – Cu-Au-Ag-S-Te ± Co-Bi-Se. There are also significant differences between signatures of individual deposits (and their spatial clusters). In particular, the Ernest Henry and several nearby deposits are characterised by a particularly complex multi-element geochemical signature – Cu-Au-Ag-S-Te-As-Bi-Mo-W-Co-Se-Re ± Pb-Ba-In-U-Sb-Sn-Hg.

In addition to copper and gold, IOCG deposits in the district are also significantly enriched in several critical metals, most notably, Co (commonly hundreds ppm, with smaller deposits and parts of orebodies averaging >0.1% Co), REE (locally >0.5% total REE) and Re (particularly in Mo-rich deposits and orebodies affiliated with IOCG deposits sensu stricto), which could become potentially economically extractable by-products.


Biography

Vladimir Lisitsin is the manager of the Mineral System team in the Geological Survey of Queensland. He holds PhD from the University of Western Australia. His current research interests include mineral system analysis, exploration targeting and metallogeny of critical minerals.

Copper isotope fractionation in volatile-fluxed enclaves: Modern analogues for the genesis of ancient ore deposits

Mcgee, Dr Lucy1, Farkas, Dr Juraj1, Lowczak,Christopher1, Payne, Dr Justin2, Wade, Claire1,3, Reid, Dr Anthony1,3

1University Of Adelaide, Adelaide, Australia, 2University of South Australia, Adelaide, Australia, 3Geological Survey of South Australia, Adelaide, Australia

Mafic enclaves are a common feature of volcanic deposits and provide some of our best estimates of the material entering the plumbing system beneath volcanic edifices. Geochemical studies of enclaves in modern volcanic settings can be compared to ancient volcanic deposits where little is known about the tectonic history and magmatic inputs of the system. When applied to a region rich in critical minerals, such studies may provide important links between magmatic processes and genesis of economic deposits.

Mafic material has the potential to carry volatiles to the surface which may transport metal elements. Deep volatiles driven from the subducting slab also provide elemental enrichment to the mantle wedge beneath areas of potential magmatism, which could be an important precursor to ore forming magmas [1]. We compare the δ65Cu values of mafic material from ancient, mineralised terranes with modern active volcanic settings where processes and inputs are less ambiguous. We focus on the Mesoproterozoic Gawler Range Volcanics (GRV) of Southern Australia, a voluminous Silicic Large Igneous Province which contains mafic material in the form of minor basaltic lava flows and enclaves dispersed within dacites and rhyolites which range from δ65Cu -0.73 to +0.61 ±0.05. Importantly, one of the world’s most valuable Iron Oxide Copper Gold (IOCG) deposits, Olympic Dam, is associated with GRV magmatism at ca. 1590 Ma [2]. We compare these new isotopic data with analyses of mafic enclaves erupted within andesitic material between 1995 AD and 2010 AD from Soufriere Hills Volcano, Montserrat. Volcanic material from this eruption has chemical signatures suggestive of recent volatile fluxing from mafic recharge material which correlate with extremely light δ65Cu values extending to -2.4 suggesting volatile transport of Cu on rapid timescales [3].

[1] Skirrow, R., et al., 2018, G-cubed, 2018. 19(8): p. 2673-2705. [2] Reid, A., 2019, Minerals, 2019. 9(6): p. 371. [3] McGee et al., 2019, Earth Planet. Sci. Lett., 524, 115730


Biography

Lucy is a high temperature geochemist and volcanologist interested in the processes occurring in magmas. She is currently interested in using modern volcanism to inform metal transport.

Differentiated Archean dolerites and orogenic gold: Influences on fertility

Hayman, Patrick1, Campbell, Ian2, Cas, Ray3, Squire, Rick3, Doutch, David3, Outhwaite, Michael4

1Queensland University of Technology, Brisbane, Australia, 2Australian National University, Canberra, Australia, 3Monash University, Clayton, Australia, 4Lithify Pty Ltd, East Victoria Park, Australia

Granophyre and quartz dolerite are the evolved fractions of differentiated dolerite (diabase) sills and are an important host to Archean gold deposits, in part because accessory magnetite acts as a chemical reactant for orogenic fluids. Despite their economic importance, the understanding of processes leading to enhanced formation of these favorable rock types is poor. Drill core logging, whole rock geochemistry, magnetic susceptibility, gold assay and thermodynamic modelling data from eleven mineralized and unmineralized ca. 2.7 Ga differentiated dolerites in the Eastern Goldfields Superterrane (Yilgarn Craton, Western Australia) are used to better understand the igneous and emplacement processes that increase the volume of host rock favorable for gold precipitation during orogenesis. Orogenic gold favours differentiated dolerites, derived from iron-rich parental magmas, that crystallize large volumes of coarse quartz (magnetite) dolerite (>25% total thickness). Mineralized sills are commonly >150 m thick and hosted by thick sedimentary sequences. Sill thickness is likely the most important factor as it largely controls cooling rate and hence fractionation. The parental melts must have fractionated large amounts of clinopyroxene and plagioclase (possibly up to 50%) before emplacement in the shallow crust. A second fractionation event at shallow levels (<3 km) operated both vertically and laterally, resulting in an antithetic relationship between quartz (magnetite) dolerite and cumulates (pyroxenites and peridotites). By comparison with younger mafic sills emplaced in syn-sedimentary basins, we argue that the geometry of these high-level sills was more irregular than the often-assumed tabular form. Any irregularities in the lower sill margin act as traps for early formed (dense) ferromagnesian minerals, now represented by pyroxene and peridotite cumulates, while irregularities in the upper sill margin trap the buoyant fractionated liquids when the sill is mostly crystalline, through magma flow on the scale of <1 km. Late formation of magnetite (F>50%) is critical to produce disseminated texture and increase the volume of magnetite-bearing quartz dolerite; thus dry magmas are more prospective. Less Fe-enriched melts are known to host orogenic gold, but these are less common, and probably only become good hosts for economic gold when sufficiently thick to fractionate large volumes of magnetite. We summarize the characteristics of the most prospective hosts relevant for exploration of differentiated dolerites hosting orogenic gold.


Biography

Dr Hayman’s principal research focuses on using field data and geochemical techniques to resolve volcanic, tectonic and ore forming processes of the Earth at a range of scales, from outcrops to terranes.

A morphotectonic analysis of the East Manus Basin, Papua New Guinea

Dyriw, Nicholas J1,2, Bryan, Scott E1, Richards, Simon W3, Parianos, John M2, Arculus, Richard J,4 Gust, David A1

1School of Earth and Atmospheric Sciences, Queensland University of Technology, Brisbane, Queensland, Australia, 2Nautilus Minerals Ltd (now Deep Sea Mining Finance Ltd), Brisbane, Queensland, Australia, 3Independent research geologist, Brisbane, Queensland, Australia, 4Research School or Earth Sciences, Australian National University, Canberra, Australian Capital Territory, Australia.

Backarc basins develop through a continuum of evolutionary phases. Surface morphology, magmatism and associated volcanism are key indicators of the various stages of development. The East Manus Basin, Papua New Guinea, is a young (<1Ma) rapidly rifting system on the eastern flank of the larger Manus Basin. Like many other backarc systems of the Southwest Pacific, numerous volcanic centers in the East Manus Basin are associated with active, Cu-Au mineralized hydrothermal systems known as seafloor massive sulfide deposits. However, not all the hydrothermal systems host significant Cu-Au mineralization and the link between the location of these seafloor massive sulfide deposits and the stages of basin evolution are unclear. Here we present the first morphotectonic description and interpretation of the East Manus Basin. Multi-resolution, multibeam echosounder seafloor data and derivatives were used in combination with the Benthic Terrain Modeler for ArcGIS to investigate seafloor characteristics, including volcano morphology and structural lineaments, and define three evolutionary phases for the East Manus Basin. Phase 1 is a period of incipient extension of existing arc crust. Phase 2 evolves to incipient crustal rifting and a transition to effusive volcanism. Phase 3 progresses to nascent organized half-graben system with axial volcanism. Intersecting rift-parallel and rift-oblique structures are important extension accommodation zones and, at the transition between Phase 1 to Phase 2, host the most significant Cu-Au seafloor massive sulfide system within the East Manus Basin. This relationship suggests the accommodation structures developed during early basin evolution may be critical to focus fluid and magma for seafloor massive sulfide formation. Furthermore, the morphotectonic features and relationships associated with modern backarc basin evolution will help to improve interpreting fossilized backarc systems around the world.


Biography

Nicholas is completing his PhD at the Queensland University of Technology (QUT). His fields of research include marine geoscience and magmatic-hydrothermal ore-forming systems. Before joining QUT, Nicholas worked as an exploration geologist for for 3 years offshore in the Southwest Pacific and in the Lachlan Fold Belt, NSW

Gold in oil, and its role in the formation of epithermal gold deposits

Crede, Lars1,2; Evans, Katy1; Rempel, Kirsten1,3, Weihua Liu4, Brugger, Joël5; Etschmann, Barbara5; Bourdet, Julian6, Reith, Frank7,*

1School of Earth and Planetary Sciences, Curtin University, Perth, Australia, 2Germany, 3McGill University, Montreal, Canada, 4CSIRO Mineral Resources, Clayton, Vic 3168, Australia, 5School of Earth, Atmosphere and the Environment, Monash University, Clayton, VIC 3800, Australia, 6CSIRO, ARRC, 26 Dick Perry Avenue, Kensington WA 6151, Australia, 7School of Biological Sciences,The University of Adelaide, Adelaide, South Australia, 5005, Australia.

* Passed away in 2019.

Gold can be associated with hydrocarbons in hydrothermal gold deposits, but the near-absence of experimental data on gold-hydrocarbon interactions at hydrothermal conditions prevents a quantitative interpretation of the significance of the observed textural relationships. We present the results of hydrothermal two phase experiments that investigate Au partitioning between aqueous and organic liquids, and a petrographic and synchrotron investigation of samples from the McLaughlin epithermal Au deposit, USA. Carbonaceous material from McLaughlin contains Au concentrations of up to 18 ppm. We conclude that remobilisation and/or transport of Au by hydrocarbon-rich liquids cannot be excluded.


Biography

Katy Evans is an Associate Professor at Curtin University. She uses thermodynamics, petrography, and geochemistry to investigate open systems, especially those involving redox transformations. Current projects include the formation of nickel deposits in the Fraser Zone, Western Australia, and effects of industrial emissions on rock art on the Burrup Penninsula.

Using epidote U-Pb geochronology and multivariate statistics to unravel overprinting propylitic alteration around the Resolution porphyry-Cu-Mo deposit: Fingerprinting the fertile porphyry signal

Phillips, Joshua1,2,, Thompson, Jay1,2, Meffre, Sebastien1,2, Maas, Roland3, Danyushevsky, Leonid1,2, Cooke, David1,2

1Australian Research Council (ARC) Research Hub for Transforming the Mining Value Chain (TMVC), University of Tasmania, Hobart, Australia, 2Centre for Ore Deposits and Earth Sciences (CODES), University of Tasmania, Hobart, Australia, 3School of Earth Science, University of Melbourne, Melbourne, Australia

The Laramide aged Resolution porphyry Cu-Mo deposit, located within the Superior mining district, Arizona, has a resource of 1,787 Mt at 1.53% Cu and 0.035% Mo, making it one of the largest and highest grade porphyry Cu deposits in North America. Tertiary gravels and volcanic rocks related to Basin and Range extension buried all but the most distal epithermal veins and propylitic alteration under approximately 1.5 km of post-mineralisation cover. Identification and mapping of the distal propylitic alteration at surface is itself hampered by a diverse range and multiple generations of epidote-chlorite alteration assemblages observed within the district that could be related to multiple orogenic and/or hydrothermal events that have affected the area over its ~1,650 m.y. history.

Here we present the development of a LA-ICP-MS method for U-Pb geochronology applied to epidote to aid in resolving multiple epidote-forming events.

Our results demonstrate the presence of at least three spatially coincident but temporally distinct epidote-bearing alteration assemblages within the Superior district of Arizona. The first of these formed yielded a U-Pb LA-ICPMS age of 1,183 ± 23 Ma, broadly coeval with the emplacement of ca. 1,100 Ma dolerite sills temporally associated with the Midcontinent rift. The second event was related to the emplacement of a 74 Ma early Laramide weakly mineralized intermediate stock. The final phase of epidote alteration had insufficient U for high-precision dating but is temporally constrained through cross cutting field relationships and relates to the 65 Ma distal propylitic halo surrounding the Resolution porphyry Cu-Mo deposit.

By constraining the relative ages of epidote-bearing alteration, It is possible to isolate the Laramide signal using LA-ICPMS mineral chemistry trace element data. Multivariate statistical classification demonstrates that the Laramide epidote and chlorite are chemically distinct from, but in some cases overgrow the Proterozoic epidote throughout the Resolution propylitic alteration halo. LA-ICPMS mapping of epidotes reveals complex growth and sector zoning within Proterozoic epidotes (enriched in As, Bi, P, REE), overgrown by a much later Laramide epidote strongly enriched in Pb and Sr.

This development in understanding between local background epidote compositions and Laramide hydrothermal epidote gives explorers new tools to more fully understand the alteration geochemistry observed within Proterozoic rocks in the SW US porphyry province and, ultimately, better target undiscovered porphyry systems.


Biography

Josh started working as a exploration geologist in 2011 in WA and NSW before completing a PhD at CODES in 2018, investigating the geochemical vectors to mineralisation at the Resolution porphyry deposit in Arizona. Since then he has worked in porphyry exploration teams for Freeport McMoRan and Fortescue Metals Group

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