The distribution of hydrocarbon minerals in the Welsh borderlands and adjacent areas

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Abstract
Solid hydrocarbon minerals occur in small quantities in the Lower Palaeozoic Welsh Basin, where Ordovician igneous intrusions mobilized them from local organic‐rich source rocks. Hydrocarbon minerals are widespread in the Wenlockian and Carboniferous Limestones, and at least in the Carboniferous Limestone they show a close and probably genetic relationship with lead‐zinc mineralization. The association of hydrocarbon minerals with lead‐zinc‐copper ores in Ordovician and Longmydian rocks' in the West Shropshire mining region is however largely coincidental. The hydrocarbon minerals in that region are residual from Carboniferous reservoir hydrocarbons. Reservoir hydrocarbon minerals in a breccia at Row Brook include crystallites of iron sulphides and manganese oxides. Hydrocarbon minerals in siderite nodules in the Coal Measures are spatially related to metal sulphides.