Pyke Asbestos Deposits, New Zealand

Babcock, R. C. Jr. ; Znamensky, V. S.
Organization: Society for Mining, Metallurgy & Exploration
Pages: 16
Publication Date: Jan 1, 1986
The Pyke asbestos deposits were discovered by Kennecott Explorations (Australia) Pty. Ltd. in 1969 during the course of base metal exploration on the South Island of New Zealand. Extensive occurrences of chrysotile asbestos were found associated with the Red Mountain ultramafics in the headwaters of the Pyke River, and to the north and south along the ultramafic belt for a distance of 70 km. Surface evaluation and drilling by Kennecott in 1970 and 1971 identified numerous small deposits of good grade fiber in the Little Red Hills between the Pyke and Barrier Rivers. Additional drilling and three adits have been completed by other companies since that time. The property is presently held by Lime and Marble, Ltd., of Nelson, New Zealand, and Kennecott Explorations (Australia) Pty. Ltd. This chapter presents the regional and local setting of the asbestos deposits, including the geology and nature of mineralization. In addition, the exploration methods used by Kennecott in the discovery and evaluation of these deposits are outlined. Subsequent work by other companies is mentioned, but not de- scribed in detail. This subsequent work did not alter Kennecott's conclusions or produce any serious changes in the interpretation of geology and mineralization. The author acknowledges the contribution of the many employees of Kennecott Explorations (Australia) Pty. Ltd. who have been involved in the project. In particular, thanks go to Ramon Farmer, N.G. Corner, and A.W. McConie, who were responsible for completion of field work and reporting on the project. The responsibility for the conclusions and interpretations of this chapter are solely that of the author and result from his involvement in the discovery of the deposits and management of the exploration program. REGIONAL SETTING Ultramafic rocks on the South Island of New Zealand are thought to be Permian in age and occur between crystaIline and metamorphic continental rocks of Precambrian through Cretaceous age in the west, are thought to have once been part of the Antarctic subcontinent, and the extensive geosynclinal graywacke deposits of the Mesozoic New Zealand geosyncline in the east. They consist of the Dun Mountain ultramafics, a 130 km long segment of ultramafic rocks located at the north end of the South Island, and the Red Mountain ul- tramafics that occur in a zone 200 km long in the south half of the South Island as shown in Fig. 1. These two belts, once contiguous, have been offset a distance of 560 km by the still active Al- pine fault, which is analogous in character and offset to the San Andreas fault of the United States. The ultramafic rocks occur within a sequence of Permotriassic volcanic and sedimentary rocks that probably formed at the eastern margin of the continental plate. The ultramafics appear to be tectonically emplaced between Permian lithologies in the Dun Mountain belt (Coleman, 1966), and at the base of or between Permian volcanics and sediments in the Red Mountain belt. The Permotriassic ultramafic volcanic sequence of the Red Mountain ultramafic belt appears to be a typical ophiolite sequence. Ultramafic rocks, mixed mafic intrusive rocks and volcanics, volcanic rocks, and volcanoclastic sediments occur in apparent superposition from east to west in the area of Red Mountain. Farther south, ultramafic rocks are associated with basaltic volcanic rocks and some sediments, and still farther south are emplaced entirely in sediments. These structural compIications of the normal ophiolite sequence have resulted from the coincidence of Permian subduction, early Mesozoic extension and sedimentation, and Cretaceous subduction along the same plate margin (Landis and Bishop, 1972). The general geology in the area of the Red
Full Article Download:
(670 kb)