OF CARBONATE-HOSTED LEAD-ZINC DEPOSITS OF THE KOOTENAY ARC ( 82 FEast Half )
Fieldwork for this study consisted of a preliminary investigation and sampling of carbonate-hosted lead-zinc deposits within the Kootenay arc. Lead isotope data from galena were also determined at The University of British Columbia. Carbonate-hosted lead-zinc deposits in the Kootenay arc have been characterized as either concordant or transgressive types based on field characteristics (Fyles, 1966). In general, the transgressive mineralization occurs as vein or replacement deposits that are enriched in silver. The concordant deposits are stratiform  and  contain  a  simple  base metal sulphide mineral suite with little or no precious metals. The concordant deposits have also been referred to as the Salmo or Remac-type, after several large deposits in the Salmo camp. Lead isotope data from deposits in the Kootenay arc have been used to interpret and explain the source of lead and the ore-forming processes responsible for these deposits. Lead isotope plots for the Remac-type deposits do not conform to lead growth curves constructed for lead-zinc deposits from this region, nor can they be adequately interpreted as the result of lead mixing or lead inheritance. A thorough analysis and comparison of the ore and gangue mineralogy, stratigraphy, and trace element and isotope geochemistry from these conformable Remac-type deposits and the younger Metaline-type deposits will provide an improved understanding of the regional ore-forming process.
Stratigraphic and Structural Setting
INTRODUCTION The material which forms the basis of this project was obtained from a number of wells in the study area in Cyrenaica, the northeastern part of Libya. The study area, which is located between latitudes 25° and 33°N and between longitudes 20° and 25° E, covers some 365,750 square kilometres (see Fig. 1). The area extends from the Egyptian border in the east to the eastern flank of the Sirte Basin in the west and is part of the stable Saharan Shield. Since Precambrian time several phases of epeirogenic movements have produced troughs, horst blocks or platforms which have in turn influenced the subsequent sedimentological history of the area. In the southern and southeastern part of the study area, the basement is unconformably overlain by a thick, partially marine Palaeozoic sequence which is in turn unconformably overlain by sediments of Jurassic or younger age. The basement in the central and southwestern parts of the area is unconformably overlain by non-marine clastics of Late Jurassic and Early Cretaceous age or by marine sediments of Late Cretaceous and Tertiary age. In the eastern and northeastern section the basement is overlain by a wedge of eastward thickening marine Palaeozoic rocks which are in turn unconformably overlain by marine sediments of Late Cretaceous and Tertiary age. In the most northerly part of the northeastern region of the study area, a thick paralic sequence of Triassic, Jurassic and Early Cretaceous deposits is unconformably overlain by Late Cretaceous and Tertiary sediments. PALAEOZOIC Rocks of Cambro-Ordovician . . .
Upper Eocene-lower Oligocene benthonic foraminifera, Port Elizabeth and Cape Foulwind, New Zealand
Abstract At Port Elizabeth, type section of the Runangan Stage and of part of the Kaiatan Stage, five biostratigraphic zones based on benthonic smaller foraminifera are recognised between the lowest exposed Kaiatan strata and the Whaingaroan strata below the Cobden Limestone. The fauna gradually changes from an inner shelf type at the base of the section to an outer shelf type higher up. At Cape Foulwind only the two upper zones are represented (Runangan-Whaingaroan Stages), and the fauna remains an inner shelf type throughout the section. The climate of the region seems to have been mostly warm-temperate, except for a brief subtropical period in late Kaiatan and early Runangan times.