The Australian Mafic-Ultramafic Magmatic Events GIS Dataset : Archean, Proterozoic and Phanerozoic Magmatic Events

Brief description

The dataset is made publicly available as a GIS at nominal 1:5 000 000 scale, and shows the time-space-event distribution of mafic-ultramafic magmatism in Australia from the early Archean to the present day. Development of this GIS has been a multi-year project and earlier released extracts (in viewable pdf form with accompanying Geoscience Australia Records) included compilations for the Archean magmatic record, the Proterozoic magmatic record, and the Australian Large Igneous Provinces (LIPs). Publication of the GIS completes the series with addition of the Phanerozoic magmatic record, and formalisation of the complete record of Archean-Phanerozoic magmatic events as a single series. The chronology of Australian mafic-ultramafic magmatism resolves into 74 magmatic events within, predominately, resolvable bands of ±10 million years. Each event is identified by geological units grouped by similar age - this coeval magmatism may or may not be genetically related and may be in response to different geodynamic environments. These magmatic events range in age from the Eoarchean ~3730 Ma ME 1 - Manfred Event, confined within a small remnant domain within the Yilgarn Craton, to the widespread record of Cenozoic magmatism in eastern Australia (ME 72 to ME 74). The magmatic events range in magnitude from the giant volumes of magma in Large Igneous Provinces, to events whose only known occurrence is an isolated record of dated mafic igneous rock in a single drillhole. The GIS makes it possible to focus on the location of any one of these magmatic events, or groups of magmatic events that may be of interest, and overlay context from any other information that users may have available. The delineation of magmatic events for this study is based on several hundred published ages of mafic and ultramafic igneous rocks from different isotopic systems and minerals. In addition to their ages and extents, primary recorded aspects of each magmatic event include the presence or absence of ultramafic components. Further to this, the presence or correlation of known magmatic-related mineralisation is highlighted in Time-Space-Event Charts of Australia (Appendix D, figures D1 and D2). The basis for mapping has been regional solid geology, interpreted basement geology and surface geology base maps made available by the State and Northern Territory geological surveys, providing insight into the total areal extent of the magmatic systems under cover. Also available to complement the Event GIS are the domains and element boundaries from the Australian Crustal Elements map. These boundaries which are which are based on geophysical extrapolation of crustal elements under the cover of continental basins, provide a framework of the shallow crustal structure of the continent, and are used in this guide. The Crustal Elements digital dataset is available for download from the Geoscience Australia website. Insight into the geodynamic development of the continent is provided by the magmatic event structure through time. The compilation draws attention to concentrations of mafic-ultramafic magmatism in the Archean from ~2820-2665 Ma, in the Proterozoic from ~1870-1590 Ma, and in the late Neoproterozoic-Phanerozoic from ~530-225 Ma. These three time spans contain 39 of the 74 magmatic events, 53% of the entire mafic-ultramafic magmatic event record of the continent. The periods in between have mafic-ultramafic magmatic records that are more dispersed in time. Other features of interest include the shared geographic and crustal element locations of Large Igneous Provinces and numerous events with smaller magma volumes. Read the rest of the Executive Summary in the document.

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Statement: Development of this GIS has been a multi-year project and earlier released extracts (in PDF form with accompanying Geoscience Australia Records) included compilations for the Archean magmatic record, the Proterozoic magmatic record, and the Australian Large Igneous Provinces (LIPs). Publication of the GIS completes the series with addition of the Phanerozoic magmatic record, and formalisation of the complete record of Archean-Phanerozoic magmatic events as a single series. Where available, this dataset uses existing solid geology and surface geology datasets. These were sourced from the Northern Territory Geological Survey, The Geological Survey of South Australia, the Geological Survey of Western Australia, the Geological Survey of Queensland, the Geological Survey of New South Wales, Geoscience Victoria, Mineral Resources Tasmania and Geoscience Australia's 1:1 000 000 surface geology of Australia (2010) dataset. Modifications to existing solid geology and surface geology datasets have been limited to attributions including, where necessary, changes to the original source map symbol where naming conflicts occur. In some areas, where the only available geological maps were surface geology, some geophysical interpretation has been created to define geological unit boundaries. Geological unit attribute information has been populated from the Australian stratigraphic units database.