Journey to the edge of the basin - tratigraphic setting and iron mineralisation at the Davidson Creek and Robertson Range Projects, Hamersley Province, Western Australia

摘要

The Robertson Range and Davidson Creek Projects are located in the Hamersley Province about 100 km east of Newman, Western Australia. Significant iron mineralisation within the Marra Mamba Iron Formation is shallowly north dipping at Davidson Creek, and mainly shallow east dipping at Robertson Range, forming part of a regional scale anticline with the granitic and greenstone basement of the Sylvania Inlier as its core. With minor exceptions, the stratigraphy is comparable with that seen in the main Hamersley Basin. Granite and greenstone basement rocks of the Sylvania Inlier are unconformably overlain by shale and volcanic rocks of the Fortescue Group. The overlying Hamersley Group is locally represented by interbedded chert, banded iron-formation (BIF) and shales of the Marra Mamba Iron Formation (Nammuldi, MacLeod and Mount Newman Members), and dolomite, chert, BIF and shale of the Wittenoom Formation. Iron enrichment occurs predominantly in the Mount Newman Member, and to a lesser extent in the West Angela Member of the Wittenoom Formation. Enrichment varies from 20 to 30 m in thickness in elongate bodies up to 3 km in strike length, and generally thins down dip. At Davidson Creek iron mineralisation is a hematite-goethite-ochreous goethite assemblage, whereas at Robertson Range this assemblage is consistently overprinted by a goethitic alteration related to hardcap weathering. Near surface hardcap weathering in both project areas comprises more siliceous, aluminous and vitreous goethite.