摘要:

AbstractNew (revised) data on thermodynamic properties of 60 substances are calculated by extrapolating their compressibilities and calorific properties up to 4000 K and 1 Mbar. Stability of pyrrhotite throughout the mantle supports Goldschmidt's idea about a sulphide zone between the mantle and the core. Such a zone could serve as a primary source of ores. Volatile H2O and H2S are stable throughout the mantle. Some hydrocarbons decompose into a mixture of methane and carbon over a wide range of pressures and temperatures. Natural oil may be regarded as a mixture of metastable hydrocarbons. FeO does not dissociate into a mixture of Fe2O3and Fe at high pressure and temperature. Alkali‐free carbonate magmas may arise in the mantle. The greater the proportion of iron‐silicates in the mantle, the more probable is the existence of a ferrous‐ferric garnet zone at great

ISSN:0072-1050    

DOI:10.1002/gj.3350240202

出版商:John Wiley&Sons Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractA sheet‐like appinite from Breaghy Head, North Donegal, is closely associated with a spessartite intrusion. Field, mineralogical, and geochemical similarities indicate that the parent magmas were very similar, and the appinite magma may have been derived from the spessartite by small degrees of crystal fractionation. The appinite is divided into an amphibole‐rich lower part and a felsic upper part; the mineralogical contrast between the two is best explained by two‐pulse intrusion of a batch of spessartitic magma within which amphibole and pyroxene had already segregated due to crystal settling or flow sorting. Unlike other Caledonian appinites, the Breaghy Head intrusion is not one of a cluster, and appears to be an isolated development. Possible reasons for its location are disc

ISSN:0072-1050    

DOI:10.1002/gj.3350240203

出版商:John Wiley&Sons Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractTwo formations are named in the presumed Precambrian sedimentary rocks of the Old Radnor Inlier. The Strinds Formation comprises fine‐ to medium‐grained sandstones and pebbly sandstones. Grain‐size, texture, clast types, and lithological invariance support correlation with the homogeneous and cross‐bedded sandstone facies of the Bayston‐Oakswood Formation of the Longmyndian, assigned to a braided alluvial plain environment. The Yat Wood Formation comprises fine‐grained sandstones, siltstones, and laminated mudstones. It may be equivalent to some part of the Burway, Synalds, or Lightspout Formation. The Strinds and Yat Wood Formations are petrographically similar to each other and to the type Lonmyndian, and were sourced either directly or indirectly from a magmatic arc.The Strinds and Yat Wood Formations are seen only in faulted contact, and the inlier itself is partly or wholly bounded by strands of the Church Stretton fault zone. Similar faulted relationships are seen further northeast along the system at Pedwardine and in the Church Stretton area. A fault explanation for the juxtaposition of contrasting facies is favoured over that of an original unconformity of Strinds on Yat Woo

ISSN:0072-1050    

DOI:10.1002/gj.3350240204

出版商:John Wiley&Sons Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe upper part of the Limestone Coal Group (Pendleian E1), between the major marine transgressions of the Black Metals and the Index Limestone, represents an early example of ‘coal measures’ facies. It comprises a distal and a proximal facies association. The distal facies association, which was subject to relatively strong marine influences and included both deltaic and fluvial elements, is characterized by a regular ‘layer‐cake’ succession with laterally‐persistent lithological members. By contrast, the proximal association, which was more subject to fluvial influences and is typified by the variable Bannockburn Main Complex, is characterized by abrupt lateral changes in lithofacies.The distal facies association is dominant in the west of the Kilsyth Trough, but proximal facies intercalations increase eastwards, so that they constitute a fairly high proportion of the succession in the Kincardine Basin, particularly in areas of locally‐increased tectonic subsidence that were frequently occupied by major channel belts.Some of the sheet sandstones within the distal association have a lower, upward‐coarsening portion succeeded by a coarser‐grained, erosive‐based, upward‐fining portion. The resulting ‘two‐storey’ profile may reflect deltaic sand bodies having been suceeded by fluvial sand bodies, following a general fall in base level.Linear regression lines showing the relationship between the number of horizons colonized by vegetation and net subsidence, suggest that local autocyclic, tectonosedimentary processes, such as delta switching, channel migration, and avulsion, were superimposed upon a widespread allocyclic, probably glacial‐eustatic, process. The former processes were most effective within the proximal facies association and in the Kincardine Basin and the latter in the distal assoc

ISSN:0072-1050    

DOI:10.1002/gj.3350240205

出版商:John Wiley&Sons Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe Corallian Group of the Dorset coast is reinterpreted as representing four regressive–transgressive cycles in contrast to previous interpretations which recognized four asymmetric regressive cycles. Each regressive sequence is separated at its top from each transgressive sequence by a sharp erosional contact. Overall, the regressive, coarsening‐up sequences are characterized by relatively low faunal diversity, dominantly vertical burrows, relatively coarse sediments with cross‐bedding and swaley cross‐stratification, and the diagenesis predominantly influenced by meteoric water. In comparison, the transgressive, fining‐up sequences are generally characterized by relatively high faunal diversity, dominantly horizontal burrows, basal lag deposits (1–2m in thickness) overlying a sharp, erosional surface, followed by clay or nodular wackestone and dominantly deep burial diagenesis. The consistence of the four regressive‐transgressive cycles with the eustatic sea‐level curve suggests that the sedimentary cycles of the Corallian outcrops may have been mainly produced by the eustatic sea‐level changes. Tectonic movements may have been important in generating localized unconformity, relatively coarse clastic sediment influxes and rapid lateral facies variations. The recognition of storm‐ and tidally‐related sedimentary features suggests that the Corallian Group of the Dorset coast may have been deposited in a storm‐ and tidally‐influenced sha

ISSN:0072-1050    

DOI:10.1002/gj.3350240206

出版商:John Wiley&Sons Ltd    

年代:1989

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350240208

出版商:John Wiley&Sons Ltd    

年代:1989

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350240210

出版商:John Wiley&Sons Ltd    

年代:1989

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350240211

出版商:John Wiley&Sons Ltd    

年代:1989

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350240213

出版商:John Wiley&Sons Ltd    

年代:1989

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350240214

出版商:John Wiley&Sons Ltd    

年代:1989

数据来源: WILEY