Copper-bearing breccia pipes in the Redbank area intersect an interbedded sequence of igneous and dolomitic sedimentary rocks which have undergone various degrees of metasomatism.The steeply inclined breccia pipes are of small size and cylindrical form and typically show in situ brecciation. The breccia matrix and associated veins consist essentially of various proportions of microbreccia, dolomite, quartz, chlorite, celadonite, hematite, K-feldspar, apatite, and chalcopyrite, with minor barite, rutile, galena, and pyrobitumen. K-metasomatism is most intense in the vicinity of the breccia pipes and associated veining, and there is mineralogical and textural evidence indicating that fluids enriched in K, Cl, P, Mg, Ce, La, CO 2 , and H 2 O were introduced at the time of breccia-pipe formation. Carbonate and sulfide minerals from brecciated and metasomatized rocks at lower stratigraphic levels have isotopic compositions consistent with magmatic hydrothermal derivation. However, the delta 13 C values of the great bulk of the dolomite in the breccia pipes indicate remobilization of sedimentary carbonate. Furthermore, the sulfur isotope ratios of the main sulfide mineralization, which occurs near the top of the brecciated sequence, are variable and generally enriched in 34 S relative to the minor amounts of sulfide at lower levels.It is concluded that the breccia pipes formed by explosive release of fluids following the buildup of significant over-pressure in a postulated carbonated, K-rich trachytic magma at depths of roughly 2 to 3 km beneath the surface. This was accompanied by intense metasomatism and precipitation of some carbonate and sulfide minerals which partly infilled the open spaces. The thermal gradients and fracturing caused extensive circulation of connate brine (and possibly descending sea water). The brine remobilized sedimentary and magmatic hydrothermal components in and around the pipes and copper mineralization in the Redbank area mainly precipitated from this brine.
A coefficient of elimination derived from Information Theory is proposed. The coefficient expresses the mixing of the elements C, H and O in kerogen, based on chemical analyses. It is shown to have meaning in terms of the products of kerogen evolution, as well as the changes in the chemistry of the kerogen itself. It is suggested that this parameter, plotted against percentage hydrogen, is a useful addition to the conventional van Krevelen diagram. Points representing the accepted stages of kerogen evolution are indicated with reference to the chemistry of the processes in vol ved and are shown to be similar to those determined from physical studies, in particular reflectivity.
Summary The Carboniferous rhynchonellid Terebratula pleurodon Phillips is proposed as the type species of a new genus Pleuropugnoides, characterized by its similarity to Pugnoides Weller (1910) but differing in being wholly costate. Terebratula pleurodon is also redescribed and figured, and the variation between individuals is analysed statistically and compared with that of Pleuropugnoides greenleightonensis sp. nov. from the Lower Namurian rocks of Northumberland. It is suggested that some previously described Carboniferous rhynchonellids may belong to this genus.
Summary Productus hemisphaericus J. Sowerby is redescribed and designated type species of the new genus Linoprotonia. Productus corrugatohemisphericus (Vaughan) is also redescribed and referred to the genus, together with Linoprotonia ashfellensis sp. nov. which is common in north-west England and has often been erroneously referred to P. corrugatohemisphericus. Other previously described Lower Carboniferous species showing similar external form to Linoproductus are considered to belong in the new genus Linoprotonia. An attempt is made to show the relationship between these Lower Carboniferous forms and the gigantoproductids, linoproductids and striatiferids. It is suggested that these genera may form a phylogenetic lineage.
The results of a number of experiments simulating the early diagenesis of carbonate ooids are presented and discussed. consideratin of both inorganic and organic reactions indicate that the presence and maturation of organic matter i scritica. It is suggested matter, while the inorganic reactions are likely to be controlled by the by‐products of the maturation of the oraganic matter. In gernral the results obtained show a marked similarily to the geilogical situation.
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