<div>Finding new mineral deposits hidden beneath the sedimentary cover of Australia has become a national priority, given the country’s economic dependence on natural resources and urgent demand for critical minerals for a sustainable future. A fundamental first step in finding new deposits is to characterise the depth of sedimentary cover. Excellent constraints on the sedimentary thickness can be obtained from borehole drilling or active seismic surveys. However, these approaches are expensive, impractical and with a potentially large environmental footprint in the remote regions of Australia. With over three quarters of the continent being covered in sedimentary and unconsolidated material, this poses a significant challenge to exploration.</div><div>&nbsp;</div><div>Recently, a method for estimating the sedimentary thickness using passive seismic data, the collection of which is relatively simple and low-cost, with a minimal environmental footprint was developed and applied to seismic stations in South Australia. The method uses receiver functions, specifically the delay time of the P -to- S converted phase generated at the interface of the sedimentary basement, relative to the direct-P arrival, to generate a first order estimate of the thickness of sedimentary cover. In this work we apply the same method to the vast array of seismic stations across Australia, using data from broadband stations in both permanent and temporary networks.</div><div>&nbsp;</div><div>From the new receiver function delay time results we are able to identify many features, such as the relatively young Cenozoic Eucla and Murray basins. A comparison with measurements of sedimentary thickness from local boreholes gives a straightforward predictive relationship between the delay time and the thickness, offering a simple and cheap way to characterise the sedimentary thickness in unexplored areas from passive seismic data. Abstract submitted and presented at 2023 Australian Earth Science Convention (AESC), Perth WA

<div>The architecture of the lithosphere controls the distribution of thermal, compositional and rheological interfaces. It therefore plays a fundamental role in modulating key ore-forming processes including the generation, transport, fractionation, and contamination of melts.&nbsp;Recognition of its importance has led to renewed efforts in recent years to incorporate constraints on lithospheric structure into the targeting of prospective regions for mineral exploration. One example is a suggested relationship between the genesis of porphyry copper deposits – known to be associated with evolved, silica-rich magmas – and the thickness of the crust.&nbsp;Here, using a new compilation of spot measurements, we explore the utility of crustal thickness as an exploration tool for porphyry copper deposits.</div> This Abstract was submitted & presented at the 2022 American Geophysical Union (AGU) Fall Meeting 12-16 December (https://www.agu.org/Fall-Meeting-2022)

<div><strong>Output Type: </strong>Exploring for the Future Extended Abstract</div><div><br></div><div><strong>Short Abstract: </strong>The continental crust directly hosts or underlies almost all mineral resources on which society depends. Despite its obvious importance its structure is poorly characterised. In particular, its density is surprisingly poorly constrained because it is difficult to directly image from the surface. Here we collate a global database of crustal thickness and velocity constraints. In combination with a compilation of published laboratory experimental constraints on seismic velocity at a range of pressures, we develop a scheme with which to convert seismic velocities into density as a function of pressure and temperature. We apply this approach to the Australian crystalline basement. We find that the Australian crust is highly heterogeneous, ranging in bulk density from 2.7—3.0 g cm-3. Finally, we explore the utility of our database for testing hypotheses about the location and endowment of mineral resources using porphyry copper deposits as an example. Our results provide an improved framework with which to explore the subsidence and thermal evolution of sedimentary basins, as well as probing relationships between deposit types and crustal architecture.</div><div><br></div><div><strong>Citation: </strong>Stephenson, S.N., Hoggard, M.J., Haynes, M.W., Czarnota, K. & Hejrani, B., 2024. Constraints on continental crustal thickness and density structure. In: Czarnota, K. (ed.) Exploring for the Future: Extended Abstracts, Geoscience Australia, Canberra, https://doi.org/10.26186/149336</div>