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1.
《地球化学》1974,(1):32-41
109 isotopic ages have been determined and collected in the recentten years, Most of them belong to Yenshanian, within which an early period (140--180m.y.) and a mid.late period (120-130m.y.) are distinguished. Granodiorite is predominant in early Yenshanian, and the related ore deposits are mainly of skarn character with mesothermal vein fillings being secondary in importance. During the mid-late Yenshanian, granite prevails and are accompanied by iron mineralization. From early to mid-late Yenshanian, the magmatie activity exhibites a striking regularity of variation in composition from intermediateacid servations, indicate that pegmatites in the Tanba region are related to Caledonian migmatization and have been reworked by two separated events at 120--130 m.y. (northern zone) and 70--80m.y. (southern zone) respectively. The migmatization progress has resulted in the formation of muscovite and biotite, thus offering an important eluc to the genesis of industrial muscovite. Three episodes of magmatic emplacement (590--720 m.y., 800-900 m.y., and more than 960 m.y.) in late Proterozoic times are also reeognized in this region.  相似文献   

2.
大厂花岗岩年龄及成矿时代   总被引：1，自引：0，他引：1  
The Dachang tin ore fields is one of the largest in China, where eassiterite-sulphide-type ore deposits occur. The ages of Dachang granites which are closely related to the ore deposits are discussed in this paper. Based on sixteen K-At biotite and one U-Pb zircon ages, it is suggested that Dachang granites were formed at 72--102 m.y.The cooling rates of Dachang granites have been estimated at 18.4℃/m.y. in the arly, 13.3℃/m.y. in the middle, and 4.5℃/m.y. in the late period.  相似文献   

3.
The traditional idea proposes that granites on the east and west coasts of the Pacific Ocean are different. According to field investigations of the geology of the western United States coupled with the authors' long-term studies on granites in South China, granites both in eastern China and in the western United States are similar.  相似文献   

4.
Two ophiolitic melange belts in the Late Carboniferous formations have been discovered recently in the Alxa region. One is in the Engger Us fault and possesses properties of oceanic crust. The other is in the Badain Jaran fault and shows properties of a back-arc basin. These two faults, together with the Yagan fault, constitute the important boundaries of tectonic units in the Alax region. The four tectonic units delimited by these faults are different in rock assemblages, metamorphism and geochemistry. They reflect the nature of tectonic environments in which they are found. The tectonic units may be traced and correlated to the eastern and western neighbouring areas. The formation and evolution process of the units and their interaction in the Alxa region may be described in terms of the evolution of the Palaeo-Mongolian Ocean and its continental margins.  相似文献   

5.
Age division of Nanling granites are discussed in relation to geological,stratigraphical,age and other data,The author believes that in Nanling region there exist granites of Xuefeng,Caledonian,Hercynian,Indosinian and Yenshanian ages.Five intrusive stages can be reeognized within the Yenshanian period.The granite belts of Qitianling-Jiufeng and Dadongshan-Guidong,whose ages have been in lively debate for a long time,can be considered as composite belts consisting of multistage emplacement.  相似文献   

6.
Based upon the present research stratus on Nan Ling granites and in the view of the defferenees in the opinions on the ages and periodic division of Nan Ling granites existing among some research units concerned, a proposal has been snbmitted in the paper, pointing out that it is quite necessary to launch a discussion in the deeper-going way on the problem involving the ages of Nan Ling granites and their periodic division in the journal “GEOCHIMICA”. The main topics expected to be discussed are as follows : (1) The existanec of Hereynian granites and the possibility of the formation of non-orogenic granites; (2) The divisional boundary between Yeushanian and Indonsinian granites and their distributional characteristics; (3) The periodic sub-division of Yenshanian granites and their relatiouship with mineralization ; (4) The division of the ,ages of granites older than the Caledonian period.  相似文献   

7.
The Tongbai-East Qinling Mountains, an important part of the Central orogenic belt, is one of the most important metallogenic belts in China and contains lots of orogenic-type and VMS-type (Volcanogenic Massive Sulfide type) metallogenic systems. The Dahe and Shuidongling VMS-type Cu-Zn deposits, located in the Erlangping Group in Tongbai and East Qinling Mountains, respectively, show similar geological and geochemical features. The Huoshenmiao Formation in the East Qinling region and the Liushanyan Formation in the Tongbai region are spilite-keratophyre sequences occurring in the western and eastern sides of the Nanyang Basin, respectively, and are interpreted to be equivalent to each other. The orogenic-type Au-Ag deposits can be subdivided into two styles; namely, fault- or structure-controlled (e.g. Yindonggou) and stratabound (e.g. Poshan). The Poshan and Yindongpo orogenic-type Au-Ag deposits, whose ore bodies are strictly hosted in carbonaceous strata in the Tongbai Mountains, show obvious stratabound characteristics. Their ore-fluids are enriched in K+ and SO42? and are regarded as K+-SO42? types. The Pb-isotope ratios of sulfides of the ores are extremely uniform and significantly different from those of the tectonostratigraphic terranes of the Qinling orogens except for the ore-hosting strata of the Waitoushan Formation. The Yindonggou and Xuyaogou orogenic Au-Ag deposits in the East Qinling Mountains, whose ore bodies are hosted in the faults cutting the hosting strata or granite body, show fault-controlled characteristics. Their ore-fluids belong to the Na+-Cl? type. The Pb-isotope ratios of sulfides of ores are similar to those of the northern Qinling orogenic belt. The Waitoushan Formation, dominated by carbonaceous sericite-rich schists and only occurring in Tongbai region, should be detached from the Erlangping Group, which occurs both in the western and eastern sides of the Nanyang Basin. Future ore exploration in the Tongbai-East Qinling Mountains should focus on fault-controlled Au-Ag lodes.  相似文献   

8.
西藏南部中酸性岩中锆石铀-铅计时讨论   总被引：2，自引：0，他引：2  
U-Pb isotopie geological ages were determined on more than 30 specimens of zircon,feldspar, sphene and apatite from the Kangdeee rock belt and its eastern Bome-Zayu areas in Xizang (Tibet). The study of common lead derivation and its mode of occurrence in zircon indicates that large amounts of common lead occur as sulphide-faeies minerals er exist in the cyrstal lattice of zircon, rather than introduced by contamination during analytical procedure. Described in this paper is the validity of subtracting zircon-containing common lead from the isotopie components of syngenetic galena, consequently leading te the conelusion that intermediate-acid rocks in the studied region are brought forth by late Yenshanian (120--80 m. y.) movement, It is suggested from the quantity of common lead and the difference in lead isotopic composition that the western segment of the Kangdese belt and its eastern Beme-Zayu areas may have two different material sources.  相似文献   

9.
Based on the new data of isotopic ages and geochemical analyses, three types of Mesozoic granites have been identified for the Xiong'ershan-Waifangshan region in western Henan Province: high-Ba-SrⅠ-type granite emplaced in the early stage (～160 Ma),Ⅰ-type granite in the middle stage (～130 Ma) and anorogenic A-type granite in the late stage (～115 Ma). Geochemical characteristics of the high-Ba-SrⅠ-type granite suggest that it may have been generated from the thickened lower crust by partial melting with primary residues of amphibole and garnet. Gradual increase of negative Eu anomaly and Sr content variations reflect progressive shallowing of the source regions of these granites from the early to late stage. New 40Ar/39Ar plateau ages of the early-stage Wuzhangshan granite (156.0±1.1 Ma, amphibole) and middle-stage Heyu granite (131.8±0.7 Ma, biotite) are indistinguishable from their SHRIMP U-Pb ages previous published, indicating a rapid uplift and erosion in this region. The representative anorogenic A-type granite, Taishanmiao pluton, was emplaced at～115 Ma. The evolution of the granites in this region reveals a tectonic regime change from post-collisional to anorogenic between～160 Ma and～115 Ma. The genesis of the early- and middle-stageⅠ-type granites could be linked to delamination of subducted lithosphere of the Qiniing orogenic belt, while the late-stage A-type granites represent the onset of extension and the end of orogenic process. In fact, along the Qiniing -Dabie-Sulu belt, the Mesozoic granitoids in western Henan, Dabieshan and Jiaodong regions are comparable on the basis of these temporal evolutionary stages and their initial 87Sr/86Sr ratios, which may suggest a similar geodynamic process related to the collision between the North China and Yangtze cratons.  相似文献   

10.
Based on the new data of isotopic ages and geochemical analyses, three types of Mesozoic granites have been identified for the Xiong'ershan-Waifangshan region in western Henan Province: high-Ba-SrⅠ-type granite emplaced in the early stage (～160 Ma),Ⅰ-type granite in the middle stage (～130 Ma) and anorogenic A-type granite in the late stage (～115 Ma). Geochemical characteristics of the high-Ba-SrⅠ-type granite suggest that it may have been generated from the thickened lower crust by partial melting with primary residues of amphibole and garnet. Gradual increase of negative Eu anomaly and Sr content variations reflect progressive shallowing of the source regions of these granites from the early to late stage. New 40Ar/39Ar plateau ages of the early-stage Wuzhangshan granite (156.0±1.1 Ma, amphibole) and middle-stage Heyu granite (131.8±0.7 Ma, biotite) are indistinguishable from their SHRIMP U-Pb ages previous published, indicating a rapid uplift and erosion in this region. The representative anorogenic A-type granite, Taishanmiao pluton, was emplaced at～115 Ma. The evolution of the granites in this region reveals a tectonic regime change from post-collisional to anorogenic between～160 Ma and～115 Ma. The genesis of the early- and middle-stageⅠ-type granites could be linked to delamination of subducted lithosphere of the Qiniing orogenic belt, while the late-stage A-type granites represent the onset of extension and the end of orogenic process. In fact, along the Qiniing -Dabie-Sulu belt, the Mesozoic granitoids in western Henan, Dabieshan and Jiaodong regions are comparable on the basis of these temporal evolutionary stages and their initial 87Sr/86Sr ratios, which may suggest a similar geodynamic process related to the collision between the North China and Yangtze cratons.  相似文献   

11.
Based on the new data of isotopic ages and geochemical analyses, three types of Mesozoic granites have been identified for the Xiong'ershan-Waifangshan region in western Henan Province: high-Ba-SrⅠ-type granite emplaced in the early stage (～160 Ma),Ⅰ-type granite in the middle stage (～130 Ma) and anorogenic A-type granite in the late stage (～115 Ma). Geochemical characteristics of the high-Ba-SrⅠ-type granite suggest that it may have been generated from the thickened lower crust by partial melting with primary residues of amphibole and garnet. Gradual increase of negative Eu anomaly and Sr content variations reflect progressive shallowing of the source regions of these granites from the early to late stage. New 40Ar/39Ar plateau ages of the early-stage Wuzhangshan granite (156.0±1.1 Ma, amphibole) and middle-stage Heyu granite (131.8±0.7 Ma, biotite) are indistinguishable from their SHRIMP U-Pb ages previous published, indicating a rapid uplift and erosion in this region. The representative anorogenic A-type granite, Taishanmiao pluton, was emplaced at～115 Ma. The evolution of the granites in this region reveals a tectonic regime change from post-collisional to anorogenic between～160 Ma and～115 Ma. The genesis of the early- and middle-stageⅠ-type granites could be linked to delamination of subducted lithosphere of the Qiniing orogenic belt, while the late-stage A-type granites represent the onset of extension and the end of orogenic process. In fact, along the Qiniing -Dabie-Sulu belt, the Mesozoic granitoids in western Henan, Dabieshan and Jiaodong regions are comparable on the basis of these temporal evolutionary stages and their initial 87Sr/86Sr ratios, which may suggest a similar geodynamic process related to the collision between the North China and Yangtze cratons.  相似文献   

12.
Based on the new data of isotopic ages and geochemical analyses, three types of Mesozoic granites have been identified for the Xiong'ershan-Waifangshan region in western Henan Province: high-Ba-Sr I-type granite emplaced in the early stage (～160 Ma), I-type granite in the middle stage (～130 Ma) and anorogenic A-type granite in the late stage (～115 Ma).Geochemical characteristics of the high-Ba-Sr I-type granite suggest that it may have been generated from the thickened lower crust by partial melting with primary residues of amphibole and garnet. Gradual increase of negative Eu anomaly and Sr content variations reflect progressive shallowing of the source regions of these granites from the early to late stage. New 40Ar/39Ar plateau ages of the early-stage Wuzhangshan granite (156.0±1.1 Ma, amphibole) and middle-stage Heyu granite (131.8±0.7 Ma, biotite) are indistinguishable from their SHRIMP U-Pb ages previous published, indicating a rapid uplift and erosion in this region. The representative anorogenic A-type granite, Taishanmiao pluton, was emplaced at ～115 Ma. The evolution of the granites in this region reveals a tectonic regime change from post-collisional to anorogenic between ～160 Ma and ～115 Ma. The genesis of the early- and middle-stage I-type granites could be linked to delamination of subducted lithosphere of the Qinling orogenic belt, while the late-stage A-type granites represent the onset of extension and the end of orogenic process. In fact, along the Qinling -Dabie-Sulu belt, the Mesozoic granitoids in western Henan, Dabieshan and Jiaodong regions are comparable on the basis of these temporal evolutionary stages and their initial 87Sr/86Sr ratios,which may suggest a similar geodynamic process related to the collision between the North China and Yangtze cratons.  相似文献   

13.
In North Xinjiang there is an alkali granite belt extending in the NW-SE direction along the southern band of the Ulungur River and running parallel to the suture zone,i.e.,Aermantai-Zhaheba Ophiolitic Melange Zone ,between the Junggar Plate and the Altay Orogenic Belt.Whole -rock Rb-Sr isochron ages of the Ulungur alkali granites are within the range of 292-309Ma, showing that they were genetically connected with the latest episode of Hercynian magmatism subsequent to the syncollision S-type and post-collision uplifting I-type granitoids in the Altay region .The alkali granites are miner-alogically characterized by the occurrence of aegirine and arfvedsonite and chemically by high silicon and alkali,low calcium and magnesium and abundant high-field elements, being typical A-type granites .The alkali granites were formed in the final stage of the Hercynian calc-alkaline magmatic cycle in a very short period of time .They are in line with the post-orogenic A-type(PA-type)granites, implying that the tectonic regime was changed from compression to extension.  相似文献   

14.
汪绍年 《地球化学》1979,(4):359-365
Distributed in Guangxi Province are granites of the Szipao, the Hsuehfengian and the other three periods. Hereynian and Indosinian granites are treated in this paper as produets of a single eycle because the Permian granitism in Guangxi is thought to be eontinuity of the late Paleozoic magmatism. Although the Darongshan granite is found to have intruded into the upper Permian, but it yields an age of 231--289 m.y. This discrepaney may be due to, among other things, an inappropriate age division between the Permian and Triassic periods as set in the International Geochronological Table, and to a strong contamination.  相似文献   

15.
The origin of natural gases in central Tarim Basin is very complicated and there has been no definite conclusion in this aspect. Based on the results of systematic research on their composition and carbon isotopic characteristics, natural gases in central Tarim Basin are composed mainly of hydrocarbon gas, Ordovician natural gas with the characteristics of crude oil-cracking gas, and Carboniferous natural gas not only originating from kerogen cracking, but also from oil cracking. There are significant differences in composition and carbon isotope of natural gases between the eastern and western areas. The causes for the differences in geochemical characteristics of natural gases are presented as follows: different thermal evolution degrees of organic matter. Natural gases in the western region may have generated from the Middle- Upper Ordovician source rocks, and natural gases in the eatern region may be derived from the Cambrian source rocks, which entered into high to over mature stages; the gases migrated from west to east and caused the different compositional and carbon isotopic characteristics of natural gases; difference in the strength of thermal sulfate reduction between the eastern and western parts, with the reduction in the eastern part being stronger than that in the western part.  相似文献   

16.
徐步台 《地球化学》1984,(3):217-225
The available data on K-Ar dating of Yenshanian granites in Zhejiang Province have been summarized in the present paper. Based on K-Ar isochron ages of the granites, in conjunction with geological evidence, three episodes of granitic magmatic intrusion are distinguished as follows: the first episode--160--135 m.y., the second-130-110 m.y. and the third--105--65 m.y. Furthermore, the tempo-spacial distribution of K-Ar ages and their geotectonic implieations are also discussed.  相似文献   

17.
The Changchun–Yanji suture zone (CYSZ) in NE China is considered as the suture between the North China Craton (NCC) and Central Asian Orogenic Belt (CAOB). The geochronology, geochemistry and Sr-Nd-Hf isotopes of Early–Middle Triassic adakitic plutions from the CYSZ, are presented in this paper to discuss their petrogenesis and tectonic setting, as well as to constrain the timing and style of the Paleo-Asian Ocean''s final closure. In Early Triassic, the Dayushan pluton (ca. 250 Ma) from western CYSZ has negative εNd(t) values, bidirectional provenances (NCC and CAOB) of εHf(t), which are formed in a collision tectonic setting. In contrast, in eastern CYSZ, the early Triassic samples in Liangshan (ca. 242 Ma) were high Mg# values, positive εNd(t), single provenances (CAOB) of εHf(t) resulting from a subduction setting. In the Middle Triassic, the A-type granites in western CYSZ are found in previous studies representing a post-collisional extensional environment, whereas syn-collisional Lianyanfeng granites (ca. 237 Ma) in eastern CYSZ with low ISr and large scale εNd(t) and εHf(t) values from bidirectional provenances (NCC and CAOB), represent a collisional setting. The Paleo-Asian Ocean''s occurred in a scissor-like fashion along the CYSZ during the Triassic period.  相似文献   

18.
The latest Cretaceous magmatic activity in the eastern segment of the Lhasa terrane provides important insights for tracking the magma source and geodynamic setting of the eastern Gangdese batholith, eastward of eastern Himalayan Syntaxis. Detailed petrological, geochemical and geochronological studies of the intrusive rocks (monzodiorites and granodiorites) of the eastern Gangdese batholith are presented with monzodiorites and granodiorites giving zircon U–Pb crystallization dates of 70–66 Ma and 71–66 Ma with εHf(t) values of ?4.8 to +6.2 and ?1.9 to +5.3, respectively. These rocks are metaluminous to weakly peraluminous I-type granites showing geochemically arc-related features of enrichment in LREEs and some LILEs, e.g., Rb, Th, and U, and depletion in HREEs and some HFSEs, e.g., Nb, Ta, and Ti. The rocks are interpreted to be derived from partial melting of mantle material and juvenile crust, respectively, which are proposed to be triggered by Neo-Tethyan slab rollback during northward subduction, with both experiencing ancient crustal contamination. The studied intrusive rocks formed in a transitional geodynamic setting caused by Neo-Tethyan oceanic flat subduction to slab rollback beneath the eastern Gangdese belt during the latest Cretaceous.  相似文献   

19.
《地学前缘(英文版)》2020,11(4):1271-1287
The northern Xinjiang region is one of the most significant iron metallogenic provinces in China.Iron deposits are found mainly within three regions:the Altay,western Tianshan,and eastern Tianshan orogenic belts.Previous studies have elaborated on the genesis of Fe deposits in the Altay orogenic belt and western Tianshan.However,the geological characteristics and mineralization history of iron deposits in the eastern Tianshan are still poorly understood.In this paper I describe the geological characteristics of iron deposits in the eastern Tianshan,and discuss their genetic types as well as metallogenic-tectonic settings,Iron deposits are preferentially distributed in central and southern parts of the eastern Tianshan.The known iron deposits in the eastern Tianshan show characteristics of magmatic Fe-Ti-V(e.g.,Weiya and Niumaoquan),sedimentary-metamorphic type(e.g.,Tianhu),and iron skarn(e.g.,Hongyuntan).In addition to the abovementioned iron deposits,many iron deposits in the eastern Tianshan are hosted in submarine volcanic rocks with well-developed skarn mineral assemblages.Their geological characteristics and magnetite compositions suggest that they may belong to distal skarns.SIMS zircon U-Pb analyses suggest that the Fe-Ti oxide ores from Niumaoquan and Weiya deposits were formed at 307.7±1.3 Ma and 242.7±1.9 Ma,respectively.Combined with available isotopic age data,the timing of Fe mineralization in the eastern Tianshan can be divided into four broad intervals:Early Ordovician-Early Silurian(476-438 Ma),Carboniferous(335-303 Ma),Early Permian(295-282 Ma),and Triassic(ca.243 Ma).Each of these episodes corresponds to a period of subduction,post-collision,and intraplate tectonics during the Paleozoic and Mesozoic time.  相似文献   

20.
从中酸性的岩浆活动论西藏高原地壳运动特征   总被引：3，自引：0，他引：3  
In view of their distinct NWW trending and their decreasing geological age from north to south, intermediate-acid magmatic rocks in the southern part of Xizang can be divided into three petrographical belts in general: (1) the Kangdese belt (120--10 m.y.). The major part of the belt is mainly composed of diorite, granodiorite, etc.,more intermediate in chemical composition and ranges from 120---70 m. y. in age; (2)the Lhangoi Kangri belt (30 m. y.) ; and (8) the Himalaya belt (20--10 m. y.). From their intruding features, spatial-temporal consistency, intruding scale, petrological characters and chemical Composition, it is suggested that these three petrographical belts secm to be closely related to plate underthrust and collision. It may be concluded that the major part of the Kangdese belt is resulted from the underthrust of the Indian Ocean Plate towards the Eurasian Continental Plate while the Lhagoi Kangri belt and the Himalaya belt are the results:of collision of the Indian sub-Continental Plate overlying the .Indian Plate with the Eurasian Continental Plate.  相似文献   

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