摘要:

AbstractOn the basis of abundant geological and geophysical data, 6 terranes have been distinguished on the Qinghai‐Tibet Plateau. The plateau is a single integrated lithospheric unit although it is divided into blocks. With Amdo as a boundary, the crust may be divided into two parts with different crustal structures. The struc‐ture in the southern part is complex, while that in the northern part is simple, The current study has revealed that 8 factors such as slab subduction, overthrust and superimposition are responsible for crustal shortening and thickening in the region. The uplift of this region is possibly due to northward compression of the Indian plate and southward compression of the Eurasian plate with the former predominating. The compression led to the asthenospheric movements which were also influenced by thermal activity caused by doming at the boundary between the core and man

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1990.mp3002001.x

出版商:Geological Publishing House    

年代:1990

数据来源: WILEY

摘要:

AbstractThis paper studies, for the first time, the storm deposits of a carbonate sequence in the Sinian Zhangqu Formation in northern Anhui. In the formation, a great number of calcareous trider sponge spicules were discovered in a distal storm turbidity sequence, which have provided further evidence for the correlation of the Sinian Systems in North and South China from a view point of palaeontology.

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1990.mp3002002.x

出版商:Geological Publishing House    

年代:1990

数据来源: WILEY

摘要:

AbstractApatites occurring in sedimentary rocks are carbonate fluorapatites (C‐F apatites) with different CO2contents. During diagenesis, the C2in the C‐F apatites gradually decreased with the increasing strength of diagenesis, resulting in the systematic changes in refractive index, specific gravity, cell parameters and crystal chemistry of apatites. On the basis of X‐ray diffraction and IR spectroscopic analyses, the author proposes two parameters for determining diagenetic stages, i.e., the crystallinity index (CR) and sharpness index (SH). These two parameters serve as new criteria for the determination, which due to the common existence of phosphorous nodules and bands and argillo‐crystalline cement in sedimentary rocks, most likely have wide prospects for appl

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1990.mp3002003.x

出版商:Geological Publishing House    

年代:1990

数据来源: WILEY

摘要:

AbstractOwing to the internal relationship between material sources or mineralization ways and the difference of mineralization micro‐environments or the change of constraints, certain types of nonmetallic mineral deposits are regularly formed either simultaneously or in successive order under the control of certain association of mineralization processes in a certain geotectonic environment, thus forming a minerogenetic series of nonmetallic mineral deposits. The geological setting that controls the formation of minerogenetic series is most truly recorded in ore‐bearing formations, while the mineralization processes which are associated or surely successive are the indispensable prerequisite for the formation of the various mineral deposits of a minerogenetic series. Therefore, the minerogenetic series of nonmetallic mineral deposits can be classified according to mineral‐bearing formations and mineralization processes. Based on available data, 13 minerogenetic series are distinguished in China. The study of minerogenetic series may not only result in the enrichment of the theory of mineral deposits but also help direct mineral prospecting and give guidance in the integrated development and utillization of mineral reso

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1990.mp3002004.x

出版商:Geological Publishing House    

年代:1990

数据来源: WILEY

摘要:

AbstractThe pre‐Sinian basement on the southwestern margin of the Yangtze paraplatform consists of three metamorphic rock series of different ages. Being products of different tectonic events and environments, they differ markedly in original rock sequences, metamorphism, tectonic style and characteristics of granitoids and mineral deposits. The Late Archean Kangdian craton mainly comprises the Kangding and Julin Groups with a metamorphic age of nearly 2500 Ma. They are supracrustal rocks dominated by mafic volcanics enclosed in trondhjemitic rocks. The craton is believed to represent a granite‐greenstone terrane of Late Archaean age. There occur mineral deposits such as graphite and kyanite deposits of metamorphic origin, muscovite deposits in pegmatites and gold quartz veins in gneissic granites, banded hornblende‐magnetite mineralization and copper and zinc mineralizations related to felsic volcanics. Large V‐Ti‐bearing magnetite deposits were also formed in the mafic‐ ultramafic stratiform intrusions emplaced on the margins of the craton during the Middle Proterozoic. Copper and nickel deposits are found in several ultramafic intrusions. Extending in a north‐south direction, the Proterozoic mobile belt consists mainly of the Early Proterozoic Hekou Group and Middle Proterozoic Huili and Kunyang Groups, and they are thought to be accumulations in a Proterozoic rift trough or aulacogen. During the Early Proterozoic, the rift trough was characterized by intense volcanism and presence of iron ore deposits of volcano‐magmatic type, iron‐copper deposits of exhalative‐sedimentary type. The Mid‐Late Proterozoic of the rift trough mainly witnessed the formation of sedimentary stratiform copper deposits and submarine sedimentary iron deposits. In the wake of the emplacement of the Jinningian and Chengjiangian granites in the Late Proterozoic, skarn‐type tin and tin‐iron

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1990.mp3002005.x

出版商:Geological Publishing House    

年代:1990

数据来源: WILEY

摘要:

AbstractWarm and humid climate and gentle hilly topography have provided favourable conditions for the development of the weathering crust of the granite intrusions in the Longnan area, Jiangxi Province. REE is mostly concentrated in an adsorption state in clay in the wholly weathered zone. The rare‐earth minerals enriched in the parent rocks provided the source material for the REE enrichment. Exchangeable REE accounts for 48‐86%. Extraction experiments and stable isotopic study of clay minerals suggest that the downward infiltration of meteoric water and increasing gradient of pH values have played an important role in the enrichment of REE during the progressive weathering. Slight fractionation of individual REE can not change their distribution patterns in the profiles, which are inherited from the parent ro

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1990.mp3002006.x

出版商:Geological Publishing House    

年代:1990

数据来源: WILEY

摘要:

AbstractBased essentially on research results of calcareous nannofossils, combined with some other microfossil data and several secondary depositional breaks, this paper discusses the criteria of division and comparison of the middle and late Tertiary marine sediments, palaeogeographical and palaeoenvironmental evolution and palaeoclimates on the northern continental margin of the South China Sea, comprising the Tainan basin, Pearl River Mouth basin, Southeast Hainan basin and Beibu Gulf basin. Study shows that the upper Oligocene to Pliocene strata in the whole area consist essentially of marine sediments except in the Beibu Gulf basin. They include littoral, neritic and deltaic sediments as well as carbonate rock‐bioherm limestone. The sea advanced from southeast to northwest. During the transgression there appeared three culminations coinciding to the stages of deposition of nannofossil zones NN4‐5, NN11 and 13

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1990.mp3002007.x

出版商:Geological Publishing House    

年代:1990

数据来源: WILEY

摘要:

AbstractBased on the Rb‐Sr isotopic study of the granitoids in the Hengduan Mountains, the classification and geologic significance of whole‐ rock Rb‐ Sr isochrons as well as the factors influencing homogenization of the isotopic systems are discussed. Usually, there is no good linear correlation of isochrons for diorites and alkali‐rich intrusive rocks (including alkaline rock and alkalic granite). But by means of the external isochron of monominerals from the rocks, isochrons with good linear correlation as well as ages and Sr initial ratios with a high confidence can be obtained. In order to obtain a satisfactory isochron, the discriminant parameters should be calculated from the Rb / Sr ratios and estimated ages of samples. Only those that meet the requirements can be used as the Rb‐Sr isochrons. The quality of an isochron should be judged from three factors, i.e. correlation coefficient, MSWD and homogenizati

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1990.mp3002008.x

出版商:Geological Publishing House    

年代:1990

数据来源: WILEY