The geological results of a borehole drilled to investigate the coincidence of centres of a zonal pattern of mineralization ( Dunham 1934 ) with areas of strong negative Bouguer anomaly are presented. The presence of a granite batholith with cupolas, postulated by Bott & Masson-Smith (1957) has been proved; the top surface of the granite was found at 1281ft depth and the boring was continued to 2650 ft in granite. The section begins in the Great Limestone at the base of the Namurian; a normal succession in the Middle Limestone Group (Lower Carboniferous) is revealed, the Smiddy Limestone with Girvanella Band being reached at 1056 ft 6in. The Lower Limestone Group differs from the section in Teesdale and the Pennine escarpment; in particular, beds equivalent to the Melmerby Scar Limestone, identified by their fauna of algae, corals, and brachiopods, have a rubbly lithology and are split by bands of seatearth, sandstone, and shale. Beneath them, clastic sediments 38 ft thick with marine fossils rest on the weathered surface of the granite. Two quartz-dolerite sheets were proved; the Little Whin sill, 6ft, is in the Three Yard Limestone as at Stanhope, while the Great Whin sill, 192ft 9in, lies beneath the Jew Limestone, stratigraphically lower than in Upper Weardale. The Weardale granite, carrying biotite and abundant muscovite, has a low-dipping foliation in the upper part, but this becomes less obvious below 2225ft depth. Preliminary X-ray studies indicate that low albite, orthoclase, maximum microcline, and forms intermediate between the last two are present. Analyses of representative rocks for major and trace elements are given. Xenoliths are conspicuously absent, but aplites and pegmatites are common. The mineralogical and chemical effects of weathering before Carboniferous sedimentation, and of the mineralization, are described. The borehole was sited near the crossing of the Boltsburn lead vein (ene-wsw) and the Red fluorite-iron vein (ese-wnw), both of which dip towards it. Strong metasomatic mineralization, including green fluorite, blende, and quartz occurs in the Tynebottom, Jew, and Lower Little limestones. Numerous small veins were also cut both in the sediments and the granite. Though chalcopyrite is present against the lower sediments, there is no evidence of a concentrated copper zone. Fluorite continues into the granite, and pyrrhotine, not present above, is found from 1355 ft depth. Mineralization continues to much greater depths than have previously been proved in the area; its source presumably lies beneath the granite cupolas, which may, however, have guided the rising fluids.

Phenomenally large (up to 2 mm) oil-bearing and associated brine inclusions in fluorite from carbonatehosted, epigenetic, fluorite-calcite-(baryte) deposits of the Koh-e-Maran area are investigated using a combination of microthermometry, UV-microscopy and FTIR microspectroscopy. The liquid hydrocarbon phase in primary 'oil' inclusions is brown in colour and is dominated by saturated, low molecular weight, aliphatic hydrocarbons.Two types of mixed aqueous and 'oil' inclusions occur. Aqueous/oil types represent co-eval trapping of immiscible drops of oil and brine during primary growth. In oil/aqueous inclusions the oil appears to 'wet' the aqueous phase resulting in an odd 'dish-shaped' meniscus. The oil or liquid hydrocarbon part of the inclusion is primary but the aqueous part is thought to represent a secondary infill. The fluid inclusion evidence suggests that fluorite precipitated from a dilute (3.5wt.% NaCl) brine at temperatures around 110-140 ~ in the presence of an immiscible liquid hydrocarbon phase dominated by saturated, light hydrocarbons. This 'oil' was present as an emulsion in the aqueous fluid and the phenomenal size of the inclusions is thought to reflect the large droplet size in the emulsion. Infiltration of a more saline, calcium-enriched brine into pre-existing oil inclusions resulted in complex oil-water inclusions showing a reversal in the nature and shape of the oil-water interface due to the presence of unspecifed surfactants in the brine which affected the wetting characteristics of the oil.The homogenization temperatures and the presence of liquid petroleum inclusions are characteristic of Mississippi Valley-type (MVT) and manto-type fluorite deposits in many other parts of the world. K EY WO R O S: fluorite, oil-bearing inclusions, brine inclusions, Baluchistan, Pakistan.

Summary During the last few years evidence has been accumulating which has indicated that the junction between the Lower and Upper Carboniferous, the Viséan–Namurian junction, lies in the vicinity of the Great Limestone at the base of the Upper Limestone Group. The zonal evidence for the position of this boundary is reviewed and five new goniatite records from this part of the succession are described. Two have a direct bearing on the boundary problem— Cravenoceras leion Bisat, the basal goniatite of the Namurian, from the shales above the Great Limestone at Greenleighton quarry, Northumberland, and Cravenoceras aff. malhamense (Bisat) from the shales above the Little Limestone in Swinhope Burn, East Allendale. The base of the Namurian is now shown almost certainly to lie between the Four Fathom Limestone and the Great Limestone; the base of the latter is shown to be the nearest suitable mapping horizon for the base of the Millstone Grit Series.

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SUMMARY As a result of mining for metals, spars and coal, more subsurface data are available for the Great Cyclothem than for any other in the pre-Westphalian Carboniferous. These data, combined with a resurvey of the entire outcrop, have been used to produce an isopach map of the beds between the Great and Little limestones. Three upward-coarsening minor cycles, culminating respectively in the Low, High and Tynedale-Fourstones coals are recognised, and it is claimed that the coals represent near-chronostratigraphic horizons. The continuity of these beds is interrupted by two narrow sub-parallel belts of thicker sandstones. One, pre-dating the High Coal, is interpreted as a major palaeodistributary system. The other could be a later avulsion of this system, but as the sandstone coarsens upward, the previous view that this belt is a palaeobar is accepted, though with reservations. The varying lithology of the upper part of the cyclothem has a significant effect, both negative and positive, upon the post-Westphalian Pb Zn F Ba mineralisation.