Annual report EL 1196 Howley Siding for 15-03-1977 to 17-03-1979.

Abstract

The first annual geological report on EL 1196 was incorporated in the 'Geological report on the Brocks Creek Region', by R. Balde' and I.C. Fans, March, 1978. This is the second annual report, covering the period from 15.3.78 - 17.3.79. The exploration activities in EL 1196 during this period were carried out in two prospective areas. This annual geological report is for that reason subdivided into the following two geological reports: 1. Geological report on Quest 151. 2. Geological report on the Ban Ban amphibolite. DDH Ql5l-S/l was drilled in the centre of the Ban Ban amphibolite, which is a relatively homogeneous, plan parallel, tholeiitic body within a sedimentary sequence. The core of DDH Ql5l-S/l showed successively a thick, relative homogeneous very fine grained amphibolite, a 27m thick turbidite sequence, a 10m thick amphibolite and an 8m thick alternation of greywacke, amphibole and shale bands. The uppermost Ban Ban amphibolite in the drill hole, is of a very fine grained nature, generally. Local pheocrysts of titanaugite, large poikilitic feldspars and the occurence of microcline are characteristic features. The most abundant minerals are, biotite, muscovite, sphene, zircon, apatite, pyrrhotite, calcite, sericite, saussurite, quartz and vesuvianite. The turbidite sequence contains 17 different turbidity currents. Well developed turbidity currents show graded bedding .of relative coarser greywacke with disseminated pyrite at the bottom and at the top a lamination of fine shale and chert bands. Fine laminated biotite (muscovite) microcline adesinite and microcline quartz feldspar biotitite occur in the central part of the turbidite sequence. The association of pyrrhotite in the amphibolite and pyrite in the turbidite sequence has been noticed. CONCLUSIONS - 1. No economic sulphide mineralization was encountered in DDH Q15l-S/l, 2. The Ban Ban amphibolit is a submarine, extrusive volcanogenic lave flow, because: 2.1. turbidity currents occur in submarine basins, 2.2. The Ban Ban amphibolite lies on top of the turbidite sequence and below marine deposits of carbonaceous black shale, 2.3. The tholeiitic nature of the Ban Ban amphibolite with phenocrysts of titan-augite, poikilitic feldspars and the presence of microcline indicate a volcanic source, 2.4. The presence of pyrrhotite in the amphibolite indicates a reduced environment while the pyrite in the turbidite sequence indicates a more oxygenated environment. This corresponds very well with the model of a lava-flow into a shallow marine basin, 2.5. The simultaneous deposition of greywacke, shale and a relatively thin (l0m thick) amphibolite, below the turbidite sequence and just above the terrestrial quartzites of the Masson Formation indicates, a rapid change in environment probably enhanced by volcanic and related tectonic activity, 2.6. The presence of thin layers of volcanic material in the central part of the turbidite sequence indicates that this material comes from an earlier deposited volcanogenic layer, probably the directly underlying amphibolite, or from a contemporaneous volcanic eruption. RECOMMENDATIONS - As massive suiphide bodies are generally related to a change from basic volcanic rocks to acid volcanic rocks, it would be unusual to find a massive sulphide ore body within the tholeiitic Ban Ban amphibolite. No further work should be carried out.