Carboniferous metamorphism and partial melting of the Greenland Group in the Jackson River valley, south Westland
0
Citation
0
Reference
10
Related Paper
Abstract:
The peak conditions and timing of metamorphism have been determined for the early Paleozoic Greenland Group in south Westland, New Zealand. The Greenland Group, which is the most extensive pre-Cenozoic unit west of the Alpine Fault in Westland, is dominated by greenschist facies greywacke and argillite. However, in the Jackson River valley this unit comprises amphibolite facies pelitic and psammitic gneisses. Psammitic horizons are dominated by biotite, plagioclase and quartz. Pelitic horizons have similar mineralogy but also contain sillimanite and K–feldspar, as well as boudinaged K–feldspar-bearing leucosomes. Conventional geothermometry and thermodynamic modelling indicate that peak metamorphism occurred between 660 and 700 °C and 3.5 and 6.0 kbar. The timing of this moderately high–T/low–P event is constrained to be mid-Paleozoic by U–Th–Pb dating of overgrowths on detrital zircon (334 ± 18 Ma) and confirmed to be Carboniferous by a single population of monazite grains (343 ± 3 Ma). Greenland Group metamorphism in the Jackson River valley may represent Carboniferous high crustal heat flow in the Gondwana margin hinterland while crustal thickening was occurring closer to the subduction zone.Jimushaer sag is the main Oil and Gas unit in the eastern part of Junggar Basin,it shows good exploration prospect in Carboniferous formation by accessing to industrial oil flow of well Ji15,We can find a clear overlap and trunction featrues by the detailed study of the seismic reflection characteristics of the Carboniferous in the area,and those characteristic can be carried out a very good comparison that used for strata correlation of the Carboniferous in the area.Based on the above,we classify the Bashan Formation in Upper Carboniferous and Low Carboniferous,then we divide the tectonic units of Carboniferous in the area.These results will play an important role in the exploration of Carboniferous
Cite
Citations (0)
The Journal of the Japanese Association of Mineralogists Petrologists and Economic Geologists (1964)
Rocks of the Franciscan formation suffered a type of glaucophanitic regional metamorphism, being widely exposed in the Coast Ranges in California. The geological and petrological characters of the Franciscan metamorphism are outlined.
Cite
Citations (0)
Cite
Citations (0)
Cite
Citations (0)
What represents the Carboniferous Limestone in Devonshire, is a question that has often been asked, but has never yet been answered in a satisfactory manner. The question has recently been narrowed by the identification of the Coddon Hill Beds and the Posidonomya limestones with the shales, cherts, and limestones which overlie the mass of the Carboniferous Limestone in South Wales, and with the Pendleside Beds which occupy a similar position in Staffordshire, Derbyshire, and South Yorkshire. Dr. W. Hind considers these beds to be more intimately connected with the Upper than with the Lower Carboniferous Series, and in any case the homotaxial equivalent of the main mass of the Carboniferous Limestone must be sought for below them.
Cite
Citations (0)
Sill
Cite
Citations (0)
This family, which has been termed Orthidœ by some authors, comprises several genera and subgenera, of which Strophomena, Streptorhynchus , and Orthis alone have been found represented in Scottish Carboniferous strata. The genus Orthis forms a well characterized group, especially specifically numerous and abundant in the Silurian and Devonian systems, is considerably reduced during the Carboniferous period to appear no longer (P) in subsequent stages. Two species alone have been hitherto discovered in the Carboniferous rocks of Scotland.
Devonian
Subgenus
Cite
Citations (2)
Abstract The metamorphism of Pre-Cambrian dolerites in the Northwest Highlands is described and compared with that of basic rocks in the Southwest Highlands, Banffshire and other regions. The first products of metamorphism are not the same in every area. It is suggested that the trend of regional metamorphism differs according to the environment in which it took place, and that a sequence of changes established in one area cannot be used as a standard by which to judge the changes in other areas. In particular, rocks of high metamorphic grade have not invariably passed through stages characterized by low-grade minerals.
Sequence (biology)
Cite
Citations (20)
The Journal of the Japanese Association of Mineralogists Petrologists and Economic Geologists (1967)
Three stages metamorphism of the Tanzawa metamorphic rocks are discriminated from the data of the field and microscopic observations, regional metamorphism, contact metamorphism, and hydrothermal metamorphism. The geologic relationships among these different stages of metamorphism are obtained by examining the structure of original rocks and their metamorphism. The conclusions are as follows. 1) Regional metamorphism of the first stage was not followed immediately by the contact metamorphism of the second stage, and the meta-morphosed areas of the two stages do not coinside to each other. The plutonic mass of this district is a composite mass composed of acidic and basic facies, of which the basic plutonic rock is closely related to the regional metamorphism, while the acidic plutonic rock is related to the contact metamorphism. 2) Hydrothermal metamorphism of the third stage gave an effect over-lappling with the effects due to the metamorphism during the preceeding stages. 3) Original rocks are divided into two groupes, i.e., the rocks of the inner zone and the rocks of the outer zone. The metamorphosed area of the first stage coincide to the rocks of the inner zone, while the metamorphosed area of the second stage do not coincide to that and moreover seem to extend to the rocks of the outer zone. 4) Judging from the presence of debris of plutonic rocks in the lower part of the rocks of the outer zone, it is suggested that there might have been some geologic gap between the rocks of the outer zone and those of the inner zone. The gap is compared to that between the two stages of metamorphism, i.e. the first regional metamorphism and the second contact metamorphism.
Cite
Citations (0)