Geochemical and Geodynamic Constrain of Tholeiitic Volcanism and Related Intrusions in the Kampti Gold District, Southwest Burkina Faso: Implication for Mineral Exploration

The Kampti serie is a volcano-plutonic complex in the south-eastern corner of the Houndé belt, closed to the border with Ivory Coast. The stratigraphy comprises initially: a thick sequence of tholeiitic and pillowed basalt followed by pyroclastic projections derivated from bimodal volcanism; and flowing mostly to the south. The volcanic sequence is cross-cut by mafic cumulate body, stocks of gabbro, diorite, subvolcanic dykes and lately intrude by granitoid. It is bordered to the west by the pelitic schist of the Bambela basin with minor intercalation of Tarkwa type sediment. volcanoclastic facies is dominantly plagioclase-phyric (albite +/- oligoclase), zoned plagioclase has a core of anorthoclase. Secondary mineral infilled (quartz, kutnahorite, ripidolite, clinozoisite) of spherulites and oolite highlight a general low grade metamorphism of greenschist facies affecting the complex. Based on trace element chemistry, the tholeiitic rocks present flat REE pattern contrasting with the felsic rocks more enriched in LREE and depleted in HREE. The style of the magmatism in the Kampti serie is compatible with an island arc model, describe elsewhere in the birimian. Gold mineralisation and base metal occurrences associated to the nature of rocks and tectonics highlight a polymetallic district.

METAMORPHIC EVOLUTION OF GARNET–BIOTITE–MUSCOVITE SCHIST FROM BARRU COMPLEX IN SOUTH SULAWESI, INDONESIA

This paper explains the first report in metamorphic evolution of pelitic schist from Barru Complex in South Sulawesi, Indonesia. Garnet-biotitemuscovite schist was examined petrologically to assess the metamorphic evolution history, which has implications on tectonic condition of this region. The rock mainly composed of garnet, biotite, muscovite, epidote, quartz, rutile, hematite, and plagioclase. Inclusions in the garnet preserve records of prograde stage of this rock, which are epidote, titanite, quartz, and apatite. Garnet, biotite, muscovite, quartz, rutile, and plagioclase are concluded as equilibrium assemblages at peak P-T condition of this rock, which estimated at 501–562 ºC and 0.89–0.97 GPa. The result is still on the ranges of the estimated geothermal gradient P-T path of eclogite from Bantimala Complex. Similar geothermal gradients of metamorphisms might be indicated that these metamorphic rocks were metamorphosed on the similar tectonic environments. Keywords: Pelitic schist, Barru Complex, South Sulawesi, metamorphic evolution.

Geology along the Arniko Highway between Barabise and Kodari (China-Nepal Boarder) area, central Himalaya

The area between Barabise and Kodari in central Nepal along the Arniko Highway is geologically located into Higher Himalayan Crystallines (HHC) and Lesser Himalayan Sequence (LHS) that is separated by the Main Central Thrust (MCT). The HHC consists of amphibolite facies rocks (pelitic schist, psamitic schist, pelitic gneiss and quartzite), while LHS is comprised by green schist to amphibolite facies rocks (phyllite, calcareous phyllite, garnet-mica schist, black schist, quartzite and augen gneiss) in uppermost section and carbonate (dolomite and limestone) with phyllite, and metasandstone in lower section. The MCT in the area is oriented in E-W direction with about 30° dip due north and S-C structure preserved in augen gneiss of LHS characterizes the top-to-south sense of shearing, which could be related to the movement along the MCT. Mineral lineation marked by stretched mica indicates N to NNE direction in both HHC and LHS. Metamorphism of inverse grade from biotite at stratigraphically lower most section of Kuncha Formation to garnet at the uppermost section having schist and augen gneiss is obvious close to the MCT in the section. However, the Kuncha Formation contains tiny crystals of garnet in the rocks of greenschist facies. Kyanite and sillimanite isograds are developed in pelitic and psamitic schists, and pelitic schists appeared at the basal part of HHC above the MCT. The transformation of garnet to chlorite at the margin and fractures and formation of chlorite within bulk rocks of the MCT zone and HHC are the indicators of traces of retrograde metamorphism because of dropping in pressure-temperature probably related to post deformation event.