摘要:

AbstractThrough an analysis of the earliest fossils in the Precambrian‐Cambrian boundary beds in various parts of the world, especially in the Yangtze and Siberia platforms, the author has found that the evolution of the earliest skeletal animals may be divided from older to younger into three stages. The first stage (theAnabarites‐Protohertzinafauna) is represented by theAnabarites‐Protohertzinazone of the Meishucunian Stage in the Yangtze platform and theA. trisulcatusandP. cristatazones of the Manykayn Stage in Siberia. The second stage (the earliest orthothecimorphid and mollusc fauna) is represented by theParagloborilus‐Siphogonuchiteszone of the Meishucunian Stage and theAldanocyathus sunnaginicuszone of the Tommotian Stage. The third stage (the earliest hyolithimorphid and lapworthellid fauna) is represented by theSinosachiteszone of the Meishucunian Stage and theD.regularisandD.lenaicuszones of the Tommotian Stage. The three evolutionary stages can be used as a criterion for worldwide corr

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1988.mp1003001.x

出版商:Geological Publishing House    

年代:1988

数据来源: WILEY

摘要:

AbstractAccording to differences of the protolith formations, the early Precambrian strata in the northern part of the North China platform may be divided into the stable stratigraphic region in the west and the mobile stratigraphic region in the east. Based on unconformities, either stratiragphic or tectonic, as well as significant metamorphic thermal events, the two regions may be stratigraphically defined as follows: 1) the middle Archaean Fuping Supergroup composed of the Chenzhuang and Wanzi Groups (stable areas), and the middle Archaean Qianxi Group (mobile area), whose upper limits are all dated at 2800 Ma; and 2) the upper Archaean Wutai Supergroup composed of the Longquanguan, Shizui and Taihuai Groups (stable areas), and the upper Archaean Zunhua, Dantazi and Zhuzhangzi Groups (mobile areas), whose upper limits are all dated at 2500 Ma. A correlation of the above‐mentioned units is also made. The lower Proterozoic Hutuo Group of the stable region is adjusted to comprise the Gaofan, Doucun, Dongye and Guojiazhai Groups. The upper limit of the Gaofan Group is placed at 2350 Ma, Dongye 1850 Ma and Guojiazhai (the lower limit of the Changcheng System) 1700 M

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1988.mp1003002.x

出版商:Geological Publishing House    

年代:1988

数据来源: WILEY

摘要:

AbstractAnalysis of the variations in the three‐dimensional structural forms of the tungsten veins in the Xihuashan tungsten district has proved that echelon structures of the veins were formed by the changes in stress direction that caused the breakdown of the individual single veins, and are different from the echelon faults formed in shear zones. Echelon structures of the veins were produced near the lithologic boundary as a result of the rotation of stress direction in their neighbourhood and their control of vein distribution. The change in the echelon pattern caused by the variation in the attitude of lithologic boundary surface in the district is an interesting structural phenomenon. The echelon structures also reflect the variation characteristics of adjacent veins in the process of their propagatio

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1988.mp1003003.x

出版商:Geological Publishing House    

年代:1988

数据来源: WILEY

摘要:

AbstractIn the geochemical study of sedimentation, hydrogen and oxygen isotope data are useful for a discussion on formation conditions and material sources of sediments. Hydrogen and oxygen isotope analyses were made on clays separated from the sea‐floor surface sediments at 9 stations in the western sea region of the Antarctic Peninsula. On the basis of these isotopic data and the clay mineral components and by use of statistical diagrams, it may be concluded that the clay fraction in this sea region is composed mainly of terrigenous detritus; i.e. it was formed by surface weathering or supergene alteration of the rocks from the terrigenous region in the peninsular in the presence of meteoric water. However, at least a part of montmorillonite is a marine authigenic mineral formed by alteration of submarine eruptive materials or terrigenous pyroclasts in the presence of sea water. The above result is consistent with the idea derived from the study of clay mineralog

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1988.mp1003004.x

出版商:Geological Publishing House    

年代:1988

数据来源: WILEY

摘要:

AbstractThe uranium‐bearing granites in South China can be classified into two types, namely, syntectic type and transformation type. A fairly systematic hydrogen, oxygen, carbon, sulfur isotopic study of uranium deposits related to these two types of granites has been carried out by the authors, and the results show that they have obvious differences in such aspects as ore‐forming and rock‐forming ages, properties of ore‐forming solutions and source of ore‐forming substances. The authors hold that the uranium deposits related to the syntectic type granitoids are intimately connected with magmatism in time and space, whereas the uranium deposits related to the transformation type granites, though spatially linked up with uranium‐bearing granites, should actually owe their formation to extension in the fault block movement in

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1988.mp1003005.x

出版商:Geological Publishing House    

年代:1988

数据来源: WILEY

摘要:

AbstractTin polymetallic deposits are the most important type of tin deposit in the Nanling region. Many researchers both at home and abroad consider this type of tin deposit to be the product of differentiation and evolution of granite magmas resulting from anatexis of continental crust and to be genetically related to the transformation‐type (S‐type) granitoids. In this paper, on the basis of the geological settings, petrology, REE geochemistry and strontium and oxygen isotopic compositions of 6 granite intrusions associated with tin polymetallic deposits in the Nanling region, the authors suggest that the ore‐bearing granites of this type are probably the products of differentiation and evolution of acid magmas resulting from 40–50‰ fractional crystallization of magmas formed by partial melting of the pre‐existing intermediate‐basic volcanic rocks of mantle origin in the lower crust and a small amount of sialic material and belong to crust‐mantle‐derived granitoids (approaching I‐type of B. W. Chappell and A.J.R. White, but being evidently different from the S‐type granitoid related to W, Sn, Nb,

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1988.mp1003006.x

出版商:Geological Publishing House    

年代:1988

数据来源: WILEY

摘要:

AbstractThe origin of the Luoquan Formation which occurs along the southern margin of the North China Block has long been argued. Based on recent work, the Formation is considered as a glacial sedimentary sequence partially reworked by sediment gravity flow. The major evidence for the glacigene of Luoquan Formation diamictites is as follows: 1. a striated and polished pavement with various features resulting from glacial abrasion and plucking, such as crescentic gouge, crescentic fracture, streamlined form and glaciated step; 2. unsorted diamictites with striated clast, faceted clast and iron‐shaped stone formed by glaciation; 3. rhythmite with dropstones; 4. a glacial sedimentary sequence bearing advance‐retreat cycles; and 5. wide distribution of the diamictites. Glacial deposits can be distinguished from sediment gravity flow deposits by the features mentioned above. Some characteristics of sediment gravity flow existing in the Luoquan Formation diamictites indicate that glacial deposits might have been partially reworked by sediment gravity flow. Therefore, this paper suggests that the Luoquan Formation diamictite is a result of a glacial event rather than a mud flow deposit. The primary tillites are the principal contribution of the Luoquan Formation, while sediment gravity flow deposits are the redeposited diamictites and should be termed as glacigenic sediment gravity flow depos

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1988.mp1003007.x

出版商:Geological Publishing House    

年代:1988

数据来源: WILEY

摘要:

AbstractThe paper deals with the relatively weak permeable layer in a layered structure of a slope rock mass and its effect on groundwater behaviour in the rock mass. When the whole groundwater table is declined in such type of slope rock mass, the permeability of the relatively weak permeable layer in the middle will be several times lower than that of the upper and lower permeable layers and consequently the water level in layers of different permeability will fall in different rates which will lead to a discontinuous phenomenon of the water body. A method of finite element simulation on a vertical two‐dimensional profile is suggested for the study of the phenomenon and its application to practical situation is described. The calculation result shows that the existing weak permeable layer in a layered slope rock mass exerts unnegligible influence on the variation of water level in the rock mass of a slope. The result also proves the applicability of the finite element simulation metho

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1988.mp1003008.x

出版商:Geological Publishing House    

年代:1988

数据来源: WILEY