Alkaline and related rocks are a relatively rare class of igneous rocks worldwide. Alkaline rocks encompass a wide range of rock types and are mineralogically and geochemically diverse. They are typically though to have been derived by generally small to very small degrees of partial melting of a wide range of mantle compositions. As such these rocks have the potential to convey considerable information on the evolution of the Earth’s mantle (asthenosphere and lithosphere), particularly the role of metasomatism which may have been important in their generation or to which such rocks may themselves have contributed. Such rocks, by their unique compositions and or enriched source protoliths, also have considerable metallogenic potential, e.g., diamonds, Th, U, Zr, Hf, Nb, Ta, REEs. It is evident that the geographic occurrences of many of these rock types are also important, and may relate to presence of old cratons, craton margins or major lithospheric breaks. Finally, many alkaline rocks also carry with them mantle xenoliths providing a snapshot of the lithospheric mantle composition at the time of their emplacement. Accordingly, although alkaline and related rocks comprise only a volumetrically minor component of the geology of Australia, they are of considerable importance to studies of lithospheric composition, evolution and architecture and to helping constrain the temporal evolution of the lithosphere, as well as more directly to metallogenesis and mineralisation. This contribution presents data on the distribution and geology of Australian alkaline and related rocks of Mesozoic age. The report and accompanying GIS document the distribution, age, lithology, mineralogy and other characteristics of these rocks (e.g., extrusive/intrusive, presence of mantle xenoliths, presence of diamonds), as well as references for data sources and descriptions. The report also reviews the nomenclature of alkaline rocks and classification procedures. GIS metadata are documented in the appendices.

The Mesozoic alkaline and related igneous rocks of Australia web map service depicts the spatial representation of the alkaline and related rocks of Mesozoic age.

The Mesozoic alkaline and related igneous rocks of Australia web map service depicts the spatial representation of the alkaline and related rocks of Mesozoic age.

The Mesozoic alkaline and related igneous rocks of Australia web map service depicts the spatial representation of the alkaline and related rocks of Mesozoic age.

<div>This contribution presents the distribution and geology of Australian alkaline and related rocks of Paleozoic age, one in a series within the Alkaline Rocks Atlas of Australia that collectively document alkaline rocks across the continent through time. </div><div><br></div><div>In general, alkaline and related rocks are a relatively rare class of igneous rocks worldwide. Alkaline rocks encompass a wide range of rock types and are mineralogically and geochemically diverse. They are typically thought to have been derived by generally small to very small degrees of partial melting of a wide range of mantle compositions. As such these rocks have the potential to convey considerable information on the evolution of the Earth’s mantle (asthenosphere and lithosphere), particularly the role of metasomatism, which may have been important in their generation, or to which such rocks may themselves have contributed. Such rocks, by their unique compositions and/or enrichments in their source protoliths, also have considerable metallogenic potential, e.g., diamonds, Th, U, Zr, Hf, Nb, Ta, REEs. It is evident that the geographic occurrences of many of these rock types are also important, and may relate to presence of old cratons, craton margins or major lithospheric breaks. Finally, many alkaline rocks also carry with them mantle xenoliths providing a snapshot of the lithospheric mantle composition at the time of their emplacement.</div><div><br></div><div>Accordingly, although alkaline and related rocks comprise only a volumetrically minor component of the geology of Australia, they are of considerable importance to studies of lithospheric composition, evolution and architecture and to helping constrain the temporal evolution of the lithosphere. They are also directly related to metallogenesis and mineralisation, particularly for a number of the critical minerals, e.g., rare earth elements, niobium. In light of this, Geoscience Australia is undertaking a compilation of the distribution and geology of Australian alkaline and related rocks, of all ages, and producing a GIS and associated database of such rocks, to both document such rocks and for use in metallogenic and mineral potential studies.&nbsp;</div><div><br></div><div>The broadening of the definition of alkaline rocks within the Alkaline Rocks Atlas herein, to include ultra-high K mafic to felsic silica-saturated rocks (alkaline-shoshonites), which are commonly formed at convergent margin settings, manifests in some divergences in the presentation of alkaline rocks that are particularly relevant to the Phanerozoic, and Paleozoic Australia in particular.&nbsp;</div><div><br></div><div>Paleozoic alkaline and related rocks occur throughout eastern Australia, with occurrences in the Northern Territory, and in all States excluding Western Australia. However, with a few exceptions they are principally located within the Tasman Element, and are over-represented in NSW – with respect to other states jurisdictions (based on available data). Paleozoic alkaline rocks range from ultramafic through to felsic, and from strongly alkaline (undersaturated) through to mildly alkaline.&nbsp;</div><div><br></div><div>Strongly alkaline rocks – congruent with the outline of alkaline rocks presented above – are comparatively rare in the Paleozoic, and are compositionally diverse incorporating alkali basalt, kimberlite, carbonatite-related rocks, and lamprophyre, with wide-ranging ages.&nbsp;</div><div><br></div><div>Overwhelmingly, the Paleozoic alkaline rock compilation is dominated by very high K alkali mafic to felsic silica-saturated rocks. Mafic-intermediate rocks within this grouping typically have an “arc signature” (i.e., low Nb/Y) but incorporate both arc magmas as well as rocks associated with backarc rifting. These rocks typically occur within rock units or packages that comprise a diverse array of rock types and compositions from volcanic rocks, related volcaniclastics and epiclastics through to sedimentary rocks. Igneous rocks within these packages commonly range from subalkaline / calc-alkaline through to mildly alkaline (trachybasalt to trachyandesite, and less commonly trachyte) based on alkali contents. Quartz-saturated felsic alkaline rocks are dominated by near peralkaline–peralkaline A-types and high-temperature transitional I-A compositions, but locally include rarer mildly alkaline (based on HFSE) rocks. The inclusion of whole rock units, which may only incorporate a small volume of alkaline rocks, necessarily means that the volume of these alkaline rocks is both poorly constrained and over-represented with this dataset.</div><div><br></div>

Alkaline and related rocks are a relatively rare class of igneous rocks worldwide. Alkaline rocks encompass a wide range of rock types and are mineralogically and geochemically diverse. They are typically though to have been derived by generally small to very small degrees of partial melting of a wide range of mantle compositions. As such these rocks have the potential to convey considerable information on the evolution of the Earth’s mantle (asthenosphere and lithosphere), particularly the role of metasomatism which may have been important in their generation or to which such rocks may themselves have contributed. Such rocks, by their unique compositions and or enriched source protoliths, also have considerable metallogenic potential, e.g., diamonds, Th, U, Zr, Hf, Nb, Ta, REEs. It is evident that the geographic occurrences of many of these rock types are also important, and may relate to presence of old cratons, craton margins or major lithospheric breaks. Finally, many alkaline rocks also carry with them mantle xenoliths providing a snapshot of the lithospheric mantle composition at the time of their emplacement. Accordingly, although Alkaline and related rocks comprise only a volumetrically minor component of the geology of Australia, they are of considerable importance to studies of lithospheric composition, evolution and architecture and to helping constrain the temporal evolution of the lithosphere, as well as more directly to metallogenesis and mineralisation. This contribution presents the first part of an ongoing compilation of the distribution and geology of alkaline and related rocks throughout Australia. The report and accompanying GIS document alkaline and related rocks of Archean age. All are from the Pilbara and Yilgarn Cratons of Western Australia. The report also reviews the nomenclature of alkaline rocks and classification procedures. GIS metadata is documented in the appendices.

<div>Alkaline igneous and related rocks are recognised as a significant source of the critical minerals essential for Australia’s transition to net-zero. Understanding these small but economically significant group of poorly mapped rocks is essential for identifying their resource potential. The Australian Alkaline Rocks Atlas aims to capture all known occurrences of these volumetrically minor, but important, igneous rocks in a national compilation, to aid understanding of their composition, distribution and age at the continental scale. The Atlas, comprises five, stand-alone data packages covering the Archean, Proterozoic, Paleozoic, Mesozoic and Cenozoic eras. Each data package includes a GIS database and detailed accompanying report that informs alkaline rock nomenclature, classification procedures, individual units and their grouping into alkaline provinces based on common age, characteristics and inferred genesis. The Alkaline Rocks Atlas will form a foundation for more expansive research on related mineral systems and their corresponding economic potential being undertaken as part of the EFTF program. To illustrate the use of the Alkaline Rocks Atlas, a mineral potential assessment using a subset of the Atlas has been undertaken for carbonatite-related rare earth element mineral systems that aims to support mineral exploration and land-use decision making that aims to support mineral exploration and land-use decision making.</div>

<div>The Proterozoic alkaline and related igneous rocks of Australia is a surface geology compilation of alkaline and related igneous rocks of Proterozoic age in Australia. This dataset is one of five datasets, with compilations for Archean, Paleozoic, Mesozoic and Cenozoic alkaline and related igneous rocks already released.</div><div><br></div><div>Geological units are represented as polygon and point geometries and, are attributed with information that includes, but is not limited to, stratigraphic nomenclature and hierarchy, age, lithology, composition, proportion of alkaline rocks, body morphology, unit expression, emplacement type, presence of mantle xenoliths and diamonds, and primary data source. Source data for the geological unit polygons provided in Data Quality LINEAGE. Geological units are grouped into informal geographic “alkaline provinces”, which are represented as polygon geometries, and attributed with information similar to that provided for the geological units.</div>

<div>Alkaline and related rocks are a relatively rare class of igneous rocks worldwide. Alkaline rocks encompass a wide range of rock types and are mineralogically and geochemically diverse. They are typically though to have been derived by generally small to very small degrees of partial melting of a wide range of mantle compositions. As such these rocks have the potential to convey considerable information on the evolution of the Earth’s mantle (asthenosphere and lithosphere), particularly the role of metasomatism which may have been important in their generation or to which such rocks may themselves have contributed. Such rocks, by their unique compositions and or enriched source protoliths, also have considerable metallogenic potential, e.g., diamonds, Th, U, Zr, Hf, Nb, Ta, REEs. It is evident that the geographic occurrences of many of these rock types are also important, and may relate to presence of old cratons, craton margins or major lithospheric breaks. Finally, many alkaline rocks also carry with them mantle xenoliths providing a snapshot of the lithospheric mantle composition at the time of their emplacement.</div><div><br></div><div>Accordingly, although Alkaline and related rocks comprise only a volumetrically minor component of the geology of Australia, they are of considerable importance to studies of lithospheric composition, evolution and architecture and to helping constrain the temporal evolution of the lithosphere, as well as more directly to metallogenesis and mineralisation.</div><div><br></div><div>This GIS product is part of an ongoing compilation of the distribution and geology of alkaline and related rocks throughout Australia. The accompanying report document alkaline and related rocks of Paleozoic age.</div>

<div>Alkaline and related rocks are a relatively rare class of igneous rocks worldwide. Alkaline rocks encompass a wide range of rock types and are mineralogically and geochemically diverse. They are typically though to have been derived by generally small to very small degrees of partial melting of a wide range of mantle compositions. As such these rocks have the potential to convey considerable information on the evolution of the Earth’s mantle (asthenosphere and lithosphere), particularly the role of metasomatism which may have been important in their generation or to which such rocks may themselves have contributed. Such rocks, by their unique compositions and or enriched source protoliths, also have considerable metallogenic potential, e.g., diamonds, Th, U, Zr, Hf, Nb, Ta, REEs. It is evident that the geographic occurrences of many of these rock types are also important, and may relate to presence of old cratons, craton margins or major lithospheric breaks. Finally, many alkaline rocks also carry with them mantle xenoliths providing a snapshot of the lithospheric mantle composition at the time of their emplacement.</div><div><br></div><div>Accordingly, although Alkaline and related rocks comprise only a volumetrically minor component of the geology of Australia, they are of considerable importance to studies of lithospheric composition, evolution and architecture and to helping constrain the temporal evolution of the lithosphere, as well as more directly to metallogenesis and mineralisation.</div><div><br></div><div>This GIS product is part of an ongoing compilation of the distribution and geology of alkaline and related rocks throughout Australia. The accompanying report document alkaline and related rocks of Cenozoic age.</div>