Lakehead University Geology - Journal Yearbook (Thunder Bay, Ontario Canada)

Page 42 text:

GENERAL STRATIGRAPHY AND TRACE ELEMENT DISTRIBUTION OF THE SEDIMENTS OF BLACK BAY, LAKE SUPERIOR R. D. Middaugh During the late summer of 1970 a reconnaisance survey of the bottom sediments of Black Bay was carried out. The sampling was done from a Boston Whaler using a Phleger gravity corer and a Ponar grab sampler. Unfortunately, due to weather conditions only 32 stations were completed. Samples, on being brought to the laboratory underwent various analysis. Grain size analysis were done using sieve and pipette methods. The Ph and Eh were recorded at the top and at various depths along the length of the core. The cores were split and logged and samples were taken at various intervals of x-ray diffractometer analysis and for trace element analysis using the Atomic Absorption unit. The trace elements analysed for were Cu, Fe, Mn, Cr, and Ni. Results of the x-ray diffractometer analysis indicate that there are three units present. 1) Glacially derived clay, 2) post glacial intermediate clay, 3) upper recent sediments. These units are conformable in the deeper parts of the bay but exhibit erosional contacts near the more shallow margins. The geochemical data indicate that the trace element concentrations are independ- ent of grain size. The data would also seem to indicate that the trace element concentrations are fairly uniform and show no anomalous values either vertically or horizontally relative to the lithology of the sediments of Black Bay. EXPERIENCE : Summer 1968 - General mapping and core logging in the Papaskwasati Basin and the Otish Mountains in North Central Quebec. Spring 1969, 70, 71 - Limnological studies of Lake Superior under J. S. Mothersill and Canada Centre for Inland Waters. 40

Page 41 text:

THE STRUCTURE, STRATIGRAPHY AND PETROLOGY OF THE NORTH END OF THE ABITIBI BLOCK 7, STURGEON LAKE, ONTARIO Lou Covello The Sturgeon Lake greenstone belt is typical of the rhyolite-andesite-basalt assemblage of Archean metavolcanic rocks in the Canadian Shield. It consists of thick volcano-sedimentary pile, broadly symformal in morphology with a central outcropping of infolded coarse, poorly sorted metasediments flanked to the north and south by the main metavolcanic sequence. The entire greenstone belt is engulfed in a gneissic basement complex and intruded by numerous late Archean granitic plutons. The north end of Abitibi Block 7 comprises a sequence of felsic and intermediate metavolcanics lying on the south side of the greenstone belt. Detailed mapping of this area has revealed the lithology to have a uniform east-west strike and near vertical dip. Individual rock units are essentially lens-like and relatively undeformed. Metamorphism is of greenschist facies, the common mineral assemblage being quartz, albite, carbonate ± chlorite, ± epidote, ± muscovite, ± chloritoid. Rhyolitic and rhyo-dacitic rocks tend to be pyroclastic in origin, while more mafic members often occur as pillow lavas, or vesicular and massive flows with minor pyroclastic and ash-flow type interbeds. PAST EXPERIENCE: 2 summers with Ontario Department of Mines in Timmins and Sault Ste. Marie, Ontario. 2 summers with Anaconda out of the Lakehead. 1 winter with Planet Mining of Sydney, Australia in North Queensland and Victoria. 1 summer with Noranda Exploration in Northwestern Quebec. 1 year with Mattagami Lake Mines, Sturgeon Lake, Ontario. 39

Page 43 text:

Experience: Ontario Department of Mines - I 968 Ontario Department of Mines - 196-9 Projex Ltd. - 1970 AMPHIBOLES AND PYROXENES FROM THE SYENTITIC ROCKS OF COLDWELL ALKALINE COMPLEX, THUNDER BAY, ONTARIO M. C. Lee Amphiboles and pyroxenes are separated from the rock specimens which are syenites and nepheline syenites from the Coldwell Alakaline Complex. The amphiboles and pyroxenes are determined by both optical and x-ray powder methods. The 2V angles, extinction angles and refractive indexes (a, 3, y ) are determined for these specimens. The pyroxenes are found to be soda augite, aegirine-augite and augite. Zoning is observed; there is an enrichment in aegirine content towards the rim of the crystals. The amphiboles determined by the optical studies are proved to be ferrohastingsite, hastingsite, and also some riebeckite. Zoning is also observed; the iron content increases from the center towards the rim of the crystals. Optical determination is a much better method than that of x-ray for these minerals. X-ray determination is a failure for the pyroxenes and amphiboles. It is due to the fact that the cell parameters of diposide is very similar to those of aegirine and augite. The same factor affects the x-ray determination of amphiboles; the cell parameters of riebeckite is very similar to those of ferrohastingste and arfverdsonite . The course of crystallization of these pyroxenes seems to be:- soda augite - aegirine-augite - Aegirine. According to Aoki (1954) as well as Yaki (1966), crystallization in the mentioned trend takes place under low temperature and high oxygen partial pressure conditions. When the crystallization trend is moving towards the aegirine-rich members, the temperature is decreasing gradually and the oxygen partial pressure is increasing simultaneously . From the analytical results; the sequence; - Ferrohastingsite - Arfvedsonite is suspected to be continuous. Formerly, both riebeckite and arfredsonite are suspected to be the final end product. The presence of riebeckite in some rock specimens of Coldwell Complex has shown that riebeckite is the final end member of the series. 41