Evaluation Report Mud Tank Carbonatite Complex NT

Abstract

This report covers work carried out on Authority 681 covering the Mud Tank Carbonatite during the first six months of tenure. The carbonatite complex is located 85km NNE of Alice Springs however road access is approximately 160km from Alice Springs. Previous investigations have spanned over forty years from initial discovery in 1940. Previous investigations have been summarized by the NTGS which carried out an extensive soil augering program in the 1970's. The carbonatite lies in an area of generally subdued relief and has occupied a drainage axis region for much of the Tertiary. Drainage appears to be controlled by a major NE trending landsat lineament. Zircon Hill has solution cavities developed unlike the other hills on the carbonatite which are indurated channel floors of abandoned paleochannels. Weathering is controlled by lithology, elevation and surface water availability. 2.4km of costeans were excavated and a series of mica dominated intrusives, amphibolite intrusives, carbonate and feldspathic pegmatites and carbonate intrusives were mapped and sampled. Many of the carbonate and mica rich rocks appear to be cumulates. Current depth of exposure of the carbonatite complex is in a plutonic environment. Development of secondary amphiboles, including asbestos is evident; however asbestos does not appear to be common or widespread. Contacts of the carbonatite with the host gneisses, schists and granulites were exposed in several costeans. Some contacts are faulted while others appear to be intrusive contacts. Major mylonite zones are present in parts of the carbonatite complex and have pulverized the mica rich rocks in some cases, eliminating economic potential. Numerous types of mica occurrence are present, however, only one type of mica bearing unit appears to have significant economic potential. Channel sampling of the costeans on five metre intervals was carried out and samples submitted for exfoliation testing. Results were not reliable and bulk sample testing is required to indicate potential Bulk samples wele taken from ten sites, however, these have not yet been processed. Considerable evidence exists for a magmatic rather than fenitic origin for the mica rich units and bloating properties may be due to primary or deuteric alteration rather than weathering. The future field program proposed is additional costeaning to delineate maximum tonneage potential followed by augering to test depth potential. Laboratory testing will concentrate on bulk sample testing through commercial exfoliators. Current zircon mining is carried out on highly enriched heavy mineral lags, colluvium and paleochannel deposits. Considerable additional resources of zircon are likely to be present around Zircon Hill but overburden depth increases rapidly off Zircon Hill.