*This is an abstract only. No full paper is available for this abstract.* This paper introduces a new down-plunge projection method that allows geologists to rapidly determine the first-order structural geometries of mineral deposits. The method assumes that the mineralised bodies under analysis resulted when hydrothermal fluids flowed through highly permeable zones that were formed from deformation. Therefore, the grade patterns should mimic the significant structures that controlled the fluid flow. Once these structural geometries are determined, the patterns can be used to simplify, speed up and substantially increase the accuracy of the geological modelling processes of both explicit and implicit methods of modelling._x000D_
Down-plunge projection, or down-structure method, is a way to examine structures on a geological map by orientating it so as to look down into and along the direction of the plunging structural features, such as folds and fault intersections. This method of deriving true sectional geological structural geometries from an oblique viewing angle has been known to geologists for more than 100 years; however, this practical technique has not been extensively used in the field of economic geology, even though the application is very broad and relevant to the interpretation of grade distribution in mineral deposits. This century-old graphical methodology is reintroduced in this paper by combining it with a computer rendering technique called maximum intensity projection (MIP). MIP is a 2D projection method that displays the highest value point of a point cloud along a line-of-sight orthogonal to the computer screen. This allows the geologist to see through' a dense 3D grade point cloud on a computer monitor and aids structural interpretation of the details of the high-grade core that is surrounded by low-grade values. Because the rendering method appears to allow the skeletal core of a grade data set to be visualised through a low-grade surrounding, it is informally termed the X-ray' method of grade data visualisation._x000D_
Originally developed for the medical industry in 1989, MIP is highly relevant for interpreting drill hole sampled grade data. A geologist with structural geological analytical experience can rapidly identify the structural controls of mineral deposits, often within minutes of viewing the data, simply by applying the X-ray view and also viewing parallel to the down-plunge direction. Such rapid and accurate geological interpretations using X-ray plunge projection are not possible with full 3D modelling methods (including implicit modelling), which are relatively more complex and expensive than MIP; however, when combined with either explicit or implicit modelling, the X-ray plunge projection technique can result in very accurate geological models for resource evaluation purposes._x000D_
While the geologist requires no experience in 3D modelling, relevant theoretical knowledge of structural geological and field experience is essential for the accurate use of X-ray plunge projection. Without appropriate structural experience, it is difficult to interpret the range of possible structural scenarios that could be controlling the grade distribution in a mineral deposit._x000D_
A structural geological framework determined from X-ray plunge projection is an essential requirement for accurate geological modelling using implicit modelling software. Without this framework the geological modelling is left entirely to algorithmic methods of modelling, which are often devoid of geological logic and are unlikely to yield geologically sensible results. These black box' methods are becoming the primary workflows implemented in the design of implicit modelling software products, but if left unchecked such modelling practices are likely to greatly increase the chance of geological misinterpretation of data, which in turn will adversely affect the resource evaluation of mineral deposits._x000D_
CITATION: Cowan, E J, 2014. X-ray plunge projection' - understanding structural geology from grade data, in Proceedings Ninth International Mining Geology Conference 2014, pp 313-314 (The Australasian Institute of Mining and Metallurgy: Melbourne).