Aluminium in coexisting pyroxenes as a sensitive indicator of changes in metamorphic grade within the Mafic Granulite Terrane of the Fraser Range,Western Australia     

Allan F. Wilson 《Contributions to Mineralogy and Petrology》1976,56(3):255-277

Three pairs of coexisting pyroxenes of mafic granulites from each of two locations 100 km apart show large chemical differences, especially in Al, Fe, Mn, Ti and Na. Al content of the pyroxenes at the higher pressure locality is more nearly independent of Al of the host rock than are the pyroxenes from the lower pressure locality. All the data confirm that although no significant difference in temperature has emerged, there was a large difference in pressure between the two localities. Al is found to be a more effective discriminant of metamorphic conditions than . As the three pairs of pyroxenes cover a wide range of Fe at each locality, the close relationship of Al and Na (and of Ca-tschermak and jadeite) to Fe becomes evident. This shows that a normalizing procedure should be adopted before comparing localities with different Al, Mn, Ti, Na and other elements or derived components such as jadeite and Ca-tschermak.  相似文献   

Distribution and source of tar on the Pacific Ocean     

C.S Wong  David R Green  Walter J Cretney 《Marine pollution bulletin》1976,7(6):102-106

Petroleum residues, or tar lumps, are concentrated in the northwestern portion of the Pacific Ocean, particularly in the Kuroshio current system. The source of the tar appears to be tank washings from tankers on the very large Middle East to Japan route. Tar pollutants apparently are discharged by tankers south of Japan, become entrained in the Kuroshio current, and create a plume of contamination which extends downstream for 7000 km across the Pacific.  相似文献   

Modulation of short waves by long waves     

Allan M. Reece Jr. 《Boundary-Layer Meteorology》1978,13(1-4):203-214

The amplitude, wavelength, and frequency of short waves in the presence of waves of a longer scale vary in a manner that is related in phase to the long-wave profile. The purpose of this study is to observe and quantify the change in the variance of short-wave slope that occurs as a result of the change in short-wave position along a coincident long wave, during the active generation of the short-wave field by wind. To this end, measurements of wave-slope time series are made in a laboratory environment where the long-scale waves are generated mechanically and the short scale are generated primarily by air flow. The frequency variation of the short waves, as measured along the long-wave profile, is described by considering the waves to be linearly advected by the longer waves. The peak-to-peak variation along the long-wave profile of the short-wave slope variance for a given frequency band is commonly found to be 10% of its mean value. The magnitude of the excursions become smaller as short-wave frequency increases, and larger as wind speed increases. The maximum value of the short-wave slope variance generally leads the long-wave profile curve by 45 ° to 180 °.  相似文献   

Reply to comments on “Ray tracing through models of the East African Rift” by W.T.C. Sowerbutts     

A.G. Green 《Earth and Planetary Science Letters》1977,35(3):459-460

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Garnet in silicic liquids and its possible use as a P-T indicator   总被引：1，自引：0，他引：1  

T. H. Green 《Contributions to Mineralogy and Petrology》1977,65(1):59-67

Melting experiments on a model pelitic composition yield low-spessartine garnet as an important residual phase at pressures above 7 kb. The K _D values for distribution of iron and magnesium between coexisting garnet and liquid in the pelitic composition are mainly sensitive to temperature, but also have a small pressure dependence. At temperatures above 950 ° C garnet has a higher value than coexisting liquid, but below 950 ° C the garnet value is lower than that of the coexisting liquid. Thus at temperatures below 950 ° C silicic magmas may fractionate garnet and produce more magnesian derivative liquids.Reconnaissance experiments with added MnO content in the model pelite demonstrate that spessartine-rich garnets are stable in silicic liquids to pressures as low as 3 kb. The MnO and CaO contents of the experimentally crystallized garnets show an antipathetic relation. Also, the grossular content of near-liquidus garnets crystallizing from a range of compositions increases with increasing pressure. The spessartine and grossular contents of most natural garnets in eastern Australian granitic rocks suggest that these garnets formed at pressures greater than 5 kb. Increased spessartine content allows crystallization of garnet in equilibrium with a silicic magma well within the pressure limit of stability of cordierite, provided the garnet contains 10 mol.% spessartine. Thus the depth range over which garnet and cordierite may coexist in a silicic melt is broadened, subject to the availability of MnO. The effect of increased Mn content on the low-pressure stability limit of garnet may also explain the lack of resorption of some garnets in granitic magmas, as these magmas rise to shallower levels. These euhedral garnets characteristically show zoning from an Mn-poor core (typically <4 % MnO) to an Mn-richer rim (typically >4 % MnO) and may reflect continued growth of the garnet in a low pressure regime, stabilized by Mn concentrated in the residual liquid fractions of the crystallizing magma.  相似文献   

Variations in the content and distribution of n-alkanes in a series of carboniferous vitrinites and sporinites of bituminous rank     

J. Allan  A.G. Douglas 《Geochimica et cosmochimica acta》1977,41(9):1223-1230

n-Alkanes in the soluble organic matter extracted from a series of vitrinite and sporinite concentrates have been analysed by gas chromatography. The macerals were isolated from coals ranging in rank from 77.1% to 86.6% carbon (vitrinite: dry, ash-free), and yields of n-alkanes ranged from 10 to 580 ppm for vitrinites and from 20 to 970 ppm for sporinites. The maximum yields were found at a rank of 85.4% C from vitrinites and 86.6% C from sporinites.Distribution maxima of the n-alkanes, as shown by gas chromatography, range from C₂₇ and C₂₉ at lower ranks to as low as C₁₆ at higher ranks. The distributions also show a progressive decrease in the preference of odd-carbon-number homologues with increasing rank. Virtually smooth distributions were attained in high-volatile bituminous A coals. Quantitative data show that the loss of the odd-carbon-number preference occurred, for the most part, while individual long-chain homologues increased in concentration.There is a progressive increase in the amounts of shorter-chain n-alkanes with increasing rank. It is suggested that sequential processes may have occurred whereby the rate of formation of long-chain n-alkanes in high-volatile bituminous A rank macerals becomes slower than their rate of subsequent fragmentation to shorter chain lengths. Consequently, assuming derivation from the insoluble maceral matrices, the chain-length distributions of parent n-alkyl structures within the insoluble material may retain characteristics pertaining more to the nature of the source organic matter at the time of deposition than do the extractable n-alkane patterns, especially at higher ranks.  相似文献   

Generation of basaltic magma: H. S. Yoder, 1976, National Academy of Sciences Publishing Office,Washington, DC. US$5.50, 265 pp     

D.H. Green 《Geochimica et cosmochimica acta》1977,41(10):1537

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The precise measurement of earth strain     

Ronald Green 《Tectonophysics》1974,23(4):361-371

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Cordierite breakdown under high-pressure,hydrous conditions     

Trevor H. Green  R. H. Vernon 《Contributions to Mineralogy and Petrology》1974,46(3):215-226

Clear evidence exists for a cordierite breakdown reaction to amphibole-kyanite-quartz in high-grade metamorphic rocks of the Arunta Complex, Australia. Using the natural minerals this reaction has been duplicated experimentally. It proceeds over a divariant band with a slope of 12±4 bars/°C, occurring between 8 and 10.4 kb at 750° C and between 9.5 and 11.3 kb at 850°C. The reaction is cut off at low temperature by the appearance of talc and at high temperature by the appearance of orthopyroxene. The maximum pressure stability of the amphibole-kyanite-quartz assemblage is about 20 kb. These data suggest that the natural rock was subjected to pressures of at least 8 kb at 750–850° C for high water fugacities. Other experimental data on the hydration of hypersthene and cordierite-hypersthene stability, point to a temperature below 820° C and an upper pressure limit of 9.5 kb at 750–820°C. Experiments at \(P_{{\text{H}}_{\text{2}} {\text{O}}}\) total indicate that the breakdown of cordierite to amphibole-kyanite-quartz is a hydration reaction, and occurred in the natural rock as a result of an increase of water fugacity at constant total pressure (8–9.5 kb) and temperature (750–820°C).  相似文献   

Talc-garnet-kyanite-quartz schist from an eclogite-bearing terrane,Western Tasmania     

Arne Råheim  D. H. Green 《Contributions to Mineralogy and Petrology》1974,43(3):223-231

Talc-garnet-kyanite-quartz schist occurs in an eclogite-bearing terrane in the Precambrian of Western Tasmania. It is argued that this rock was formed at a pressure of ? 10 kb and a temperature of 600°±20° C. Chemical zoning in the garnet and talc preserves evidence of increasing temperature during growth of the major minerals.  相似文献