ON THE DISTRIBUTION AND DISPERSION OE ' PLATINUM IN THE SOILS OF THE TULAMEEN ULTRA . MAFIC COMPLEX , SOUTHERN BRITISH COLUMBIA
INTRODUCTION Exploration for platinum in British Columbia is hampered by a lack of data on its distribution and behavior in the surficial environment. To obtain some of the information required and suggest practical guidelines for exploration, this study, involving systematic sampling and analysis of soils and other media in the vicinity of a platinum deposit in the Tulameen district of southwestern British Columbia, was initiated in 1988 (Fletcher. 19x9). Preliminary results of work in progress are described. Tulameen River, approximately 25 kilometres west of Prince-The field area, on Grasshopper Mountain north of the ton, is divided into the main study area, on the southern slope of the mountain, and a second, smaller area near the summit (Figure 6.2-I). The lower part is accessible by pack trail from the Tulameen River road. Several kilometres of recently constructed drill road on the north and west sides of g e o l o g y , Tulameen ultramafic c o m p l e x. B. C. Figure 6-2-1, Location of the study areas and generalized (1) Nicola Group (2) syenogabhrn. (3) dunite. (4) olivine clinopyroxenite,(5) homblendr~linopqmxenite. (6)rnyloni-tic rocks. (7) Eagle granodiorile (modified after Nixon and Rublee. 1988). Grasshopper Mountain connect with the Lawless 'Creek forestry road and provide access from both the village of Tulameen and the Coquihalla Highway. BEDROCK GEOLOGY dissected dunite core of the Tulameen ultramafic complex, a Grasshopper Mountain is the northern segment o' the Late Triassic zoned Alaskan-type ultramafic-gabbroic intrusion within metasedimentary and metavolcanic rocks c,f the Upper Triassic Nicola Group. Geology of the complex, described by Findlay (1969) and Nixon and Rublea (1988). comprises a dunite core surrounded by crudely concentric shells of olivine clinopyroxenite, hornblende c h o p r o x-enite and gabbroic rocks ((Figure 6-2-1). The focus of the current study is within the dunite :ore. The dunite is typically Fine grained, extensively sepen-tinized, and weathers buff-brown on exposed surfaces "lati-num mineralization is restricted to chromite-rich dunite (Nixon e t a /. is best exposed in the summit region and in the sub\ertical randomly distributed massive to discontinuous pods, segre-gations. schlieren and disseminated grains. Schlierel are randomly distributed thrcmughout the dunite and are thought to represent foliation-concordant remnants of former cumu-late layers (Nixon and Rublee, 1988:1. Several cons of central region of the cor'? (Bohme, 19x7). but till-covered mineralization have beer1 defined within the well-exposed areas are largely untested. platinum-iron alloys and platinum antimonides …
ALASKAN-TYPE ULTRAMAFIC ROCKS IN BRITISH COLUMBIA : NEW CONCEPTS OF THE STRUCTURE OF THE TULAMEEN COMPLEXY
Alaskan-type ultramafic rocks in British Columbia are potential hosts forcommerciallyexploitabledeposits ofplatinummetals(Rublee, 1986;Evenchicketa/., 1986)aswellas other commodities (for example, chrome, nickel, cobalt, asbestos and jade). In 1987 the British Columbia Geological Survey initiated a program designed to investigate the mineral potential of these intrusions through detailed geologic mapping and lithogeochemical sampling specifically for platinum group elements. In the first year of this project, a concerted effort is being made to more thoroughly understand one of these intrusions, the Tulameen ultramafic complex in southern British Columbia. The Tulameen complex warrants careful attention as it has been the largest producer of platinum in the province and bas been taken as a typical example of a zoned Alaskan-type ultramafic intrusion (Findlay, 1963, 1969; Evenchick et a / . , 1986). The general structure of Alaskan-type complexes is characterized by a crudely concentric outward zonation of rock types ranging from olivine-bearing to hornblende-rich or magnetite-rich clinopyroxenites about a steeply dipping dunite core (Taylor, 1967). Lesser proportions of hornblendite and mafic pegmatite usually occur as isolated masses toward the periphery of the intrusion. Typical cumulate minerals include forsteritic olivine, diopsidic augite, chromite and magnetite; orthopyroxene is characteristically absent, indicating an alkalic affinity. Gabbroic rocks associated with the intrusion are commonly tholeiitic, and in this respect the syenogabbros and syenodiorites of the Tulameen complex are unusual (Findlay, 1969).
Climatology of the cusp-related thermospheric mass density anomaly, as derived from CHAMP observations
We report on the thermospheric mass density anomaly in the vicinity of the ionospheric cusp. A systematic survey of the anomalies is presented, based on a statistical analysis of 4 years of data (2002–2005) obtained by the accelerometer onboard CHAMP. The anomalies are detected during all years and seasons in both hemispheres but with stronger signatures in the Northern Hemisphere. For the same geophysical conditions, solar flux and geomagnetic activity the anomalies in the north are larger by a factor of about 1.35. Over the course of the survey period the amplitude decreases by more than a factor of 5 while the level of solar flux reduces by a factor of 2. The anomaly strength also depends on the solar wind input. The merging electric field, E merg , is generally enhanced for about an hour before the anomaly detection. There is a quadratic response of the anomaly amplitude to E merg . For geophysical conditions of P10.7 E merg E merg , where the weight of E merg , in mV/m, is by about 50 times higher than that of the solar flux level. The solar zenith angle and the influence of particle precipitation are found to play a minor role as a controlling parameter of seasonal variation. The well-known annual variation of the thermospheric density with a minimum around June also influences the formation of the cusp anomalies. This leads to a clear hemispheric asymmetry with very weak anomalies in the south during June solstice, which is supposed to be a combined effect of the minimum in annual variation and the seasonal decrease of solar insolation in this region.