Reconstruction of the Neoproterozoic supercontinent Rodinia shows near neighbour positions of the South Indian Cratons and Western Australian Cratons. These cratonic areas are characterized by extensive Paleoproterozo...Reconstruction of the Neoproterozoic supercontinent Rodinia shows near neighbour positions of the South Indian Cratons and Western Australian Cratons. These cratonic areas are characterized by extensive Paleoproterozoic tectonism. Detailed analysis of the spatio-temporal data of the Satpura Mountains of India indicates presence of at least three episodes of Proterozoic orogeny at ~ 2100-1900 Ma, ~ 1850 Ma and ~ 1650 Ma, and associated basin development and closing. A subdued imprint of the Grenville orogeny （~ 950 Ma） is also found in rock records of this Mountain Belt. The Capricorn Orogen of Western Australia also shows three episodes of orogeny： Opthalmian-Glenburgh Orogeny （2100-1950 Ma）, Capricorn Orogeny （ ~ 1800 Ma） and Mangaroon Orogeny （ ~ 1650 Ma）, and basin opening and closing related to these tectonic movements. These broad similarities suggest their joint evolution possibly in a near neighbour posi- tion during Paleoproterozoic Era. In view of juxtaposition of the Western Australia along the east coast of India, at the position of the Eastern Ghats, during Archean, it is suggested that the breaking of this Archean megacraton at - 2400 Ma led to northward movement of the broken components and formation of the Satpura-Capricorn Orogen （at - 2100 and - 1800 Ma） due to the collision of cratonic blocks with the pre- existing northern cratonic nuclei of India and Western Australia. This is also the time of formation of thesupercontinent Columbia. A phase of basin opening followed the ~ 1800 Ma event, followed by another phase of collisional event at - 1600 Ma at the site of the Satpura--Capricorn Orogen. Subsequent evolutions of the Satpura and the Capricorn Orogens differ slightly, indicating separate evolutional history.展开更多
Proterozoic orogens commonly host a range of hydrothermal ores that form in diverse tectonic settings at different times. However, the link between mineralization and the regional-scale tectonothermal evolution of oro...Proterozoic orogens commonly host a range of hydrothermal ores that form in diverse tectonic settings at different times. However, the link between mineralization and the regional-scale tectonothermal evolution of orogens is usually not well understood, especially in areas subject to multiple hydrothermal events.Regional-scale drivers for mineral systems vary between the different classes of hydrothermal ore, but all involve an energy source and a fluid pathway to focus mineralizing fluids into the upper crust. The Mount Olympus gold deposit in the Proterozoic Capricorn Orogen of Western Australia, was regarded as an orogenic gold deposit that formed at ca. 1738 Ma during the assembly of Proterozoic Australia. However,the trace element chemistry of the pyrite crystals closely resembles those of the Carlin deposits of Nevada,with rims that display solid solution gold accompanied by elevated As, Cu, Sb, Hg, and Tl, surrounding gold-poor cores. New SHRIMP UeP b dating of xenotime intergrown with auriferous pyrite and ore-stage alteration minerals provided a weighted mean^(207) Pb*/^(206) Pb* date of 1769 ± 5 Ma, interpreted as the age of gold mineralization. This was followed by two discrete episodes of hydrothermal alteration at 1727 ± 7 Ma and 1673 ± 8 Ma. The three ages are linked to multiple reactivation of the crustal-scale Nanjilgardy Fault during repeated episodes of intracratonic reworking. The regional-scale drivers for Carlin-like gold mineralization at Mount Olympus are related to a change in tectonic regime during the final stages of the intracratonic 1820 -1770 Ma Capricorn Orogeny. Our results suggest that substantial sized Carlin-like gold deposits can form in an intracratonic setting during regional-scale crustal reworking.展开更多
Traditional approaches to develop 3D geological models employ a mix of quantitative and qualitative scientific techniques,which do not fully provide quantification of uncertainty in the constructed models and fail to ...Traditional approaches to develop 3D geological models employ a mix of quantitative and qualitative scientific techniques,which do not fully provide quantification of uncertainty in the constructed models and fail to optimally weight geological field observations against constraints from geophysical data.Here,using the Bayesian Obsidian software package,we develop a methodology to fuse lithostratigraphic field observations with aeromagnetic and gravity data to build a 3D model in a small(13.5 km×13.5 km)region of the Gascoyne Province,Western Australia.Our approach is validated by comparing 3D model results to independently-constrained geological maps and cross-sections produced by the Geological Survey of Western Australia.By fusing geological field data with aeromagnetic and gravity surveys,we show that 89%of the modelled region has>95%certainty for a particular geological unit for the given model and data.The boundaries between geological units are characterized by narrow regions with<95%certainty,which are typically 400-1000 m wide at the Earth's surface and 500-2000 m wide at depth.Beyond~4 km depth,the model requires geophysical survey data with longer wavelengths(e.g.,active seismic)to constrain the deeper subsurface.Although Obsidian was originally built for sedimentary basin problems,there is reasonable applicability to deformed terranes such as the Gascoyne Province.Ultimately,modification of the Bayesian engine to incorporate structural data will aid in developing more robust 3D models.Nevertheless,our results show that surface geological observations fused with geophysical survey data can yield reasonable 3D geological models with narrow uncertainty regions at the surface and shallow subsurface,which will be especially valuable for mineral exploration and the development of 3D geological models under cover.展开更多
文摘Reconstruction of the Neoproterozoic supercontinent Rodinia shows near neighbour positions of the South Indian Cratons and Western Australian Cratons. These cratonic areas are characterized by extensive Paleoproterozoic tectonism. Detailed analysis of the spatio-temporal data of the Satpura Mountains of India indicates presence of at least three episodes of Proterozoic orogeny at ~ 2100-1900 Ma, ~ 1850 Ma and ~ 1650 Ma, and associated basin development and closing. A subdued imprint of the Grenville orogeny （~ 950 Ma） is also found in rock records of this Mountain Belt. The Capricorn Orogen of Western Australia also shows three episodes of orogeny： Opthalmian-Glenburgh Orogeny （2100-1950 Ma）, Capricorn Orogeny （ ~ 1800 Ma） and Mangaroon Orogeny （ ~ 1650 Ma）, and basin opening and closing related to these tectonic movements. These broad similarities suggest their joint evolution possibly in a near neighbour posi- tion during Paleoproterozoic Era. In view of juxtaposition of the Western Australia along the east coast of India, at the position of the Eastern Ghats, during Archean, it is suggested that the breaking of this Archean megacraton at - 2400 Ma led to northward movement of the broken components and formation of the Satpura-Capricorn Orogen （at - 2100 and - 1800 Ma） due to the collision of cratonic blocks with the pre- existing northern cratonic nuclei of India and Western Australia. This is also the time of formation of thesupercontinent Columbia. A phase of basin opening followed the ~ 1800 Ma event, followed by another phase of collisional event at - 1600 Ma at the site of the Satpura--Capricorn Orogen. Subsequent evolutions of the Satpura and the Capricorn Orogens differ slightly, indicating separate evolutional history.
基金funded through an ARC linkage grant (LP130100922) and industry scholarship by Northern Star Resources as a part of a PhD by I. O.Fielding. S. P. the financial support of the Australian Research Council and Auscope NCRIS
文摘Proterozoic orogens commonly host a range of hydrothermal ores that form in diverse tectonic settings at different times. However, the link between mineralization and the regional-scale tectonothermal evolution of orogens is usually not well understood, especially in areas subject to multiple hydrothermal events.Regional-scale drivers for mineral systems vary between the different classes of hydrothermal ore, but all involve an energy source and a fluid pathway to focus mineralizing fluids into the upper crust. The Mount Olympus gold deposit in the Proterozoic Capricorn Orogen of Western Australia, was regarded as an orogenic gold deposit that formed at ca. 1738 Ma during the assembly of Proterozoic Australia. However,the trace element chemistry of the pyrite crystals closely resembles those of the Carlin deposits of Nevada,with rims that display solid solution gold accompanied by elevated As, Cu, Sb, Hg, and Tl, surrounding gold-poor cores. New SHRIMP UeP b dating of xenotime intergrown with auriferous pyrite and ore-stage alteration minerals provided a weighted mean^(207) Pb*/^(206) Pb* date of 1769 ± 5 Ma, interpreted as the age of gold mineralization. This was followed by two discrete episodes of hydrothermal alteration at 1727 ± 7 Ma and 1673 ± 8 Ma. The three ages are linked to multiple reactivation of the crustal-scale Nanjilgardy Fault during repeated episodes of intracratonic reworking. The regional-scale drivers for Carlin-like gold mineralization at Mount Olympus are related to a change in tectonic regime during the final stages of the intracratonic 1820 -1770 Ma Capricorn Orogeny. Our results suggest that substantial sized Carlin-like gold deposits can form in an intracratonic setting during regional-scale crustal reworking.
基金funded by the Science and Industry Endowment Fund as part of The Distal Footprints of Giant Ore Systems:UNCOVER Australia Project(RP04-063)-Capricorn Distal Footprints。
文摘Traditional approaches to develop 3D geological models employ a mix of quantitative and qualitative scientific techniques,which do not fully provide quantification of uncertainty in the constructed models and fail to optimally weight geological field observations against constraints from geophysical data.Here,using the Bayesian Obsidian software package,we develop a methodology to fuse lithostratigraphic field observations with aeromagnetic and gravity data to build a 3D model in a small(13.5 km×13.5 km)region of the Gascoyne Province,Western Australia.Our approach is validated by comparing 3D model results to independently-constrained geological maps and cross-sections produced by the Geological Survey of Western Australia.By fusing geological field data with aeromagnetic and gravity surveys,we show that 89%of the modelled region has>95%certainty for a particular geological unit for the given model and data.The boundaries between geological units are characterized by narrow regions with<95%certainty,which are typically 400-1000 m wide at the Earth's surface and 500-2000 m wide at depth.Beyond~4 km depth,the model requires geophysical survey data with longer wavelengths(e.g.,active seismic)to constrain the deeper subsurface.Although Obsidian was originally built for sedimentary basin problems,there is reasonable applicability to deformed terranes such as the Gascoyne Province.Ultimately,modification of the Bayesian engine to incorporate structural data will aid in developing more robust 3D models.Nevertheless,our results show that surface geological observations fused with geophysical survey data can yield reasonable 3D geological models with narrow uncertainty regions at the surface and shallow subsurface,which will be especially valuable for mineral exploration and the development of 3D geological models under cover.
