Abstract In this study, a regional model that defines the three-dimensional geometry of the subsurface geology beneath the complex, prospective northwestern Tasmania has been developed. This has been achieved using a series of potential field inversions constrained by surface geology, geological sections, seismic interpretations and a newly extended petrophysical dataset. Three major episodes of granitic magmatism are preserved in Tasmania: in the Neoproterozoic, Cambrian and Devonian. Granite bodies are hence considered important indicators of mineralization for explorers in an area of challenging vegetation, topography and cover sequences. Forward modelling and property-based inversions of the pre-existing geological model show that the previously interpreted subsurface geometry is not compatible with potential field data. Four sub-regions displayed a large discrepancy between calculated and observed data. This study redefines the subsurface geometries of these sub-regions through individual geometry inversions. The density and magnetic susceptibility ranges of units are further refined through property inversions. The modified geometry of the Devonian granites in the four sub-regions may be summarized as follows: 1) the Housetop Granite is relatively thin (≤5 km thickness), whereas 2) the Heemskirk and Meredith Granites are very thick and granite extends to a shallower depth between these bodies than previously interpreted. This region between plutons is thus a more prospective region than previously thought. 3) For the first time, an intrusive body underlying the eastern part of the Rocky Cape Group has been identified. Its petrophysical properties are similar to that of a granite, and its top is interpreted at a depth of >3 km. This interpreted low density (granitic) unit may be either Neoproterozoic or Devonian. 4) A new non-magnetic, low density Cambrian granite, with a minimum burial depth of 1 km, is also modelled in 3D, within the Mount Read Volcanics, in the south of the study area. Our approach, whereby sub-regions are identified for more detailed modelling, enables new constraints to be introduced in a computationally efficient way, and has general application to refining the geometry of key structures in prospective regions.

中文翻译：

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有效的区域尺度 3D 势场地球物理建模，以重新定义塔斯马尼亚西北部具有远景地质复杂性的花岗岩体的几何形状

摘要 在这项研究中，开发了一个区域模型，该模型定义了复杂的、有前景的塔斯马尼亚西北部地下地质的三维几何形状。这是通过一系列受地表地质、地质剖面、地震解释和新扩展的岩石物理数据集约束的潜在场反演实现的。塔斯马尼亚保留了三个主要的花岗岩岩浆作用：新元古代、寒武纪和泥盆纪。因此，花岗岩体被认为是具有挑战性的植被、地形和覆盖序列区域的勘探者矿化的重要指标。预先存在的地质模型的正向建模和基于属性的反演表明，先前解释的地下几何形状与潜在的现场数据不兼容。四个子区域显示计算数据和观察数据之间存在很大差异。这项研究通过单独的几何反演重新定义了这些子区域的地下几何形状。单元的密度和磁化率范围通过性质反演进一步细化。四个亚区泥盆纪花岗岩的几何变化可概括如下：1）Housetop 花岗岩相对较薄（≤5km），而 2）Heemskirk 和 Meredith 花岗岩非常厚，花岗岩延伸这些天体之间的深度比之前解释的要浅。因此，岩体之间的这个区域比以前认为的更有前景。3) 首次发现落基角群东部下伏的侵入体。其岩石物理性质类似于花岗岩，其顶部被解释为>3 公里的深度。这个解释的低密度（花岗岩）单元可能是新元古代或泥盆纪。4) 在研究区南部的雷德山火山内，一种新的非磁性、低密度寒武纪花岗岩，最小埋藏深度为 1 公里，也在 3D 中建模。我们的方法通过识别子区域以进行更详细的建模，从而能够以计算效率高的方式引入新的约束，并具有普遍适用于改进预期区域中关键结构的几何形状。最小埋藏深度为 1 公里的火山也在研究区南部的 Mount Read 火山内进行了 3D 建模。我们的方法通过识别子区域以进行更详细的建模，从而能够以计算效率高的方式引入新的约束，并具有普遍适用于改进预期区域中关键结构的几何形状。最小埋藏深度为 1 公里的火山也在研究区南部的 Mount Read 火山内进行了 3D 建模。我们的方法通过识别子区域以进行更详细的建模，从而能够以计算效率高的方式引入新的约束，并具有普遍适用于改进预期区域中关键结构的几何形状。