The Green Scrub Basalt Deposit Near Mountain Lagoon Geological Report on Sources of Igneous Rock

Abstract

An inspection of an area of basalt at a locality known as the “ Green Scrub ” near Mountain Lagoon was made on 19th June, 1961, following an application by the holders of a Permissive Occupancy for removal of basalt, Messrs. Powell, Rogan and Lewis. The area of basalt is located in the vicinity of Portion 38, Parish Wheeny, County Cook. From inspection of the aerial photographs it apparently lies astride the northern boundary of that portion. A more accurate definition of locality was not possible as the portion boundaries were not identified and the parish map shows Lagoon Creek located on the east of Portion 38 whereas the photographs indicate that this creek should flow through the portion

During March, 1961, an examination of known igneous rock occurrences in Blacktown Shire was made with a view to assessing their value as sources of aggregate and road material. During the field work and office interpretation of aerial photos a search for new and unreported deposits was made without success. The result of the investigation does not offer much hope for the establishment of a large new quarry in the area, but some areas are worthy of further investigation. Small areas of old river gravels are located in the western part of the Shire. These are discussed briefly.

Igneous intrusions in the Liverpool-Campbelltown district were recently examined and sampled, and their positions plotted on the Liverpool and Camden 1-mile maps. Not all the intrusions noted by previous observers were found. This report, therefore, is divided into two parts: in the first, those intrusions that were inspected by the writer are noted; in the second, intrusions reported by earlier investigators, but not seen by the writer, despite search, are briefly mentioned.

All specimens submitted with the exception of No. 1706 are olivine basalts typical of the minor Tertiary intrusions of eastern N.S.W. Specimen No. 1706 is of coarser grainsize, has sub-ophitic texture and is to be considered an olivine dolerite. The basalts are porphyritic in olivine and clinopyroxene except Nos. 1708, 1711 which have only one generation of clinopyroxene. In general the porphyritic pyroxene is augite but in specimens 1704, 1706 and 1710 it has sufficient purple coloration to be regarded as titanaugite. Opaque ore is relatively abundant in all specimens and is predominantly magnetite. Although there are variations in the grainsize of the groundmass