摘要:

AbstractThe debris flow formed by mass transportation of lacustrine deltaic sediments is quite unique compared with subaerial one, and is called “endogenic debris flow” in this paper. The major diagnostic features of endogenic debris flow sediments are muddy rip‐ups, sandy lumps, randomly distributed carbonaceous plant leaves and rhyotaxitic structure. However, such debris flow can not be completely generalized by the conclusion that larger granules are supported by cohesive strength of the matrix. The fact that sediments can be transported in plastic state is considered to be related with two different functions of combined clay‐water materials: serving as a matrix in texture and as an adhesive between grains. This paper also discusses the origin and sediment types of endogenic debris flow as well as the general concepts of matrix and debris flow.From the viewpoint of “true debris flow”, this paper attempts to generalize and illustrate the basic features and variation of endogenic debris flow sediments on the basis of the Bingham (Coulomb‐vis

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1992.mp5002001.x

出版商:Geological Publishing House    

年代:1992

数据来源: WILEY

摘要:

AbstractThe Middle Devonian volcanic rocks in the northern area of East Junggar, located between the Ertix and Ulungur rivers of northern Xinjiang, may be divided into basic and acid ones. It is evident that a compositional gap exists between the two groups so that the volcanic rocks are not in line with a calc‐alkaline series because the intermediate rocks are absent in the area. The fact shows that the volcanic rocks are a typical bimodal association. The formation of the bimodal association of volcanic rocks in the area was closely related to continental rifting or continental extension in the Middle Devonian. In such a tectonic setting, magmas were first produced by partial melting of the mantle. Where crustal thinning was greater, the magmas ascended and erupted on the surface directly so that the basic volcanic rocks formed, but olivine and / or partial pyroxene fractionation occurred in the magmas during their ascent through the thinning crust. On the other hand, where crustal thinning was less, ascending mantle‐derived magmas reached the lower crust and accumulated there, resulting in partial melting of the lower crust and thus giving rise to the contaminated magma which was consolidated as acid volcanic rocks on the surf

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1992.mp5002002.x

出版商:Geological Publishing House    

年代:1992

数据来源: WILEY

摘要:

AbstractA strong tectono‐magmatic thermal event has been revealed by field observations of granitic, migmatitic and metamorphic rocks in the hinterland of the Dabie Mountains. K‐Ar, Ar‐Ar and Rb‐Sr determinations show that the event took place 133–117 Ma ago (Yanshanian). Contemporaneously, a southwestward thrust‐type ductile shearing at multiple levels occurred in the lower crust or at even deeper levels, suggesting that the Dabie Mountains region was still under the influence ot strong continent‐continent overlapping tectonism of the Yangtze block under the Sino‐Korean block at depth. Metamorphic rocks of amphibolite facies, migmatites and deep structural deformations resulting from this tectonothermal event are now exposed to the surface. The present features of the Dabie Mountains thus have appeared only since ca. 100 Ma B.P. The block composed of the Dabie Group is not an uplift or shield which would have undergone a long‐

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1992.mp5002003.x

出版商:Geological Publishing House    

年代:1992

数据来源: WILEY

摘要:

AbstractNd, Sr and O isotopic study on the spilite‐keratophyre sequence in Xiqiu shows that its ?Ndvalues are in the range of 4.02–5.26, and its ?srvalues, +1.4‐2.6. According to the points of these data in the ?Nd‐T, ?Sr‐T and ?Nd‐?Srdiagrams, the spilite‐keratophyre is interpreted as being slightly contaminated by crustal materials. Its δ18O values are 3.9‐5.0%0. The depletion of18O in the rocks resulted from the influence of seawater hydro thermal alteration during or soon after the rock formation. Based on the isotopic characteristics and available geochemical data, it is believed that the spilite‐keratophyre was formed in the well‐developed island‐ arc environment during the Late Proterozoic subduction of the palaeo‐ Pacific plate beneath the southeastern marg

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1992.mp5002004.x

出版商:Geological Publishing House    

年代:1992

数据来源: WILEY

摘要:

AbstractPb isotope ratios and their variation have been measured and explained on ores of massive S‐Fe‐Au deposits hosted in the Middle‐ Upper Carboniferous, on feldspars from diorite bodies closely related to mineralization and on whole rocks from ore‐hosting strata (carbonate rocks) in the Tongling area, Anhui Province. Through a comparison of Pb isotope features of these geological bodies, it has been suggested that ore substances of the deposits were derived from ore‐hosting strata. In the meanwhile, the measurement of ore Pb isotopes of different mineralization types of the same deposit indicates that different mineralization types have distinct Pb isotope characteristics, showing the potentiality of the Pb isotopic method used in mineral ex

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1992.mp5002005.x

出版商:Geological Publishing House    

年代:1992

数据来源: WILEY

摘要:

AbstractIn order to eliminate the defect of successively separative calculations of different end‐members of a mineral and to establish a widely applicable new scheme for calculating mineral end‐members, the use of the linear programming technique is proposed to calculate simultaneously all end‐members in this paper. All calculations with the scheme under study can result in non‐ negative values. In the case of calculating end‐ members of clinopyroxene, the Eskola's molecule is introduced so as to reach stoichiometry. When certain minor elements in solid solutions are present in a remarkable amount, by adding to the equations the vectors of the corresponding end‐members and adjusting the component vectors it is possible to obtain calculation results, including those of such end‐members. The possibility of using the calculation scheme under study to estimate the Fe3+/ Fe2+ratio of a mineral from electron microprobe analysis is also discussed

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1992.mp5002006.x

出版商:Geological Publishing House    

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper gives a brief report on the latest results in litho‐, bio‐, and chrono‐stratigraphy obtained from the authors' further research on the Meishucun section during 1987–1988. More attention was paid to the study of the microtexture ofLapworthellaand some new materials of trace fossils.Phycodes pendumSeilacher, an important index for correlation, was also discovered in the Zhongyicun Member. In the Yu' anshan Member many worms, medusas and arthropods of the Chengjiang fauna have been found by other workers. A supplemental study was made on the fossil zones of the Meishucunian stage. Based on new isotopic data, the age of the Precambrian‐Cambrian boundary should now be 597 Ma. It is further suggested that point “B” remains as an optimum selection for defining the Precambrian‐Ca

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1992.mp5002007.x

出版商:Geological Publishing House    

年代:1992

数据来源: WILEY

摘要:

AbstractThe age of the Longzhaogou and Jixi Groups of coal measures in eastern Heilongjiang were previously considered to be Jurassic or mainly Jurassic. But there occur Middle Barremian‐ Early AlbianAucellina( bivalvia) fossils in the Upper Yunshan Formation of the Longzhaogou Group and the Lower Chengzihe Formation of the Jixi Group, and the Qihulin Formation of the Longzhaogou Group yields Early Cretaceous bivalve and ammonite fossils. Consequently, the geological ages of the two groups are mainly, or even all, Early Cretaceou

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1992.mp5002008.x

出版商:Geological Publishing House    

年代:1992

数据来源: WILEY