Abstract
Abstract. The locations of major gold and copper deposits on the island of New Guinea are considered by many to be controlled by a series of transfer faults that strike N–S to NE–SW, perpendicular to the long axis of the island. The premise is that these faults dilate perpendicular to the regional stress field, forming conduits for metalliferous gases and fluids to drop out of solution. However, the data on which this idea was first proposed were often not presented or, when the data were presented, were of poor quality or low resolution. We therefore present a review of the existing structural interpretations and compare these with several recently published geophysical data sets to determine if the mineralization controlling transfer faults could be observed. These data were used to produce a new lineament map of New Guinea. A comparison of the lineaments with the location of major gold and copper deposits indicates there is a link between the arc-normal structures and mineralization. However, it is only those deposits that are less than 4.5 million years old that could be associated with these structures. Gravity and seismic tomography data indicate that some of these structures could penetrate deep levels of the lithosphere, providing some support to the earlier idea that the arc-normal structures act as conduits for the younger mineral deposits of New Guinea. The gravity data can also be used to infer the location of igneous intrusions at depth, which could have brought metal-bearing fluids and gases closer to the Earth's surface. These regions might be of interest for future exploration campaigns, particularly those areas that are crosscut by deep, vertical faults. However, new exploration models are needed to explain the location of the deposits that are older than 5 Ma.
Highlights
The exploration for metalliferous deposits around the world presents a challenge as there is still much to learn about the processes that concentrate metals in particular areas
Considering (1) that we found no link between what we could identify as deeper-level basement structures in New Guinea and (2) that analogue modelling of rift systems has shown that accommodation zones oriented obliquely to perpendicular to the rift axis are not necessarily related to hard-linked strike-slip basement faults (McClay et al, 2002), it is worth considering that the lateral ramps proposed by Hill (1991) for the central Papuan Fold Belt are not associated with deeper-level faults and/or an inherited basement fabric
Our interpretation of the several different geophysical data types indicates that arc-normal lineaments do occur in New Guinea, but these structures are not as prevalent or as simple as they have previously been portrayed
Summary
The exploration for metalliferous deposits around the world presents a challenge as there is still much to learn about the processes that concentrate metals in particular areas. In the pursuit of this goal, geologists typically devise models that attempt to explain why some metals are more concentrated in particular regions One such model is that gold and copper deposits are often found along strike of other deposits (e.g. along a line or a lineament) (cf Richards et al, 2000). Lineaments are only proposed retrospectively, after several deposits have been identified The effectiveness of this technique is questionable. These lineament style analyses are commonly used by the minerals exploration industry, on the island of New Guinea because it is home to some of the world’s richest gold and/or copper deposits (e.g. Grasberg, Ok Tedi, Frieda River, Porgera and Wafi-Golpu) (Fig. 1a)
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