• Volume 65,Issue 2,1991 Table of Contents
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    • On the Geotectonics of Southern China

      1991, 65(2).

      Abstract (1526) HTML (0) PDF 0.00 Byte (87) Comment (0) Favorites

      Abstract:The tectonic nature of southern China has changed again and again in the Phanerozoic. In the Caledoniancycle, there existed three tectonic units——the Yangtze paraplatform, Indosinian-South China Sea paraplatformand Caledonian South China fold belt, of which the last unit is not a collisional orogenic belt but ascissor-shaped aulacogen-type geosyncline opening towards Yunnan and Vietnam. In the Indosinian cycle,South China belonged to the Tethyan tectonic domain, and no abyssal oceanic basin existed there. Since theLate Triassic, especially in the Yanshanian orogenic stage, it became a component part of the peri-Pacificcontinental-margin activation belt of eastern Asia. No Alpinc-type orogenic belt occurs in the interior of thecontinent of southern China.

    • A Study on the Kunyang Aulacogen

      1991, 65(2).

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      Abstract:The Kunyang Aulacogen is a continental rift which initiated at the beginning of the Middle Proterozoic. Itwas generated on the rigid continental crust represented by the crystalline Kangding Complex, and is boundedby two N-S-trending deep faults--Anninghe-Luzhijiang Fault and Xiaojiang Fault. Its early stage of rupturewas characterized by alkalinc mafic igneous activities in the Dahongshan Group and Hekou Group. Duringthe later tensile-depression stage the aulacogen evolved into a graben where scdimentation of the KunyangGroup took place. The sedimentary sequence comprises terrestrial red beds, algal dolomite, marine black shaleand carbonate rocks which are quite typical of rift sedimentary association, and contains stratabound copperdeposits of the well-known Dongchuan type.

    • The Origin of the Mesozoic Associated Multiseries Granitoid Magma in the Shandong Peninsula

      1991, 65(2).

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      Abstract:Three melting events of the earth's crust occurred during the period of 220-120 Ma in the Shandong Pe-ninsula. Three subcycles of granitoid magma including six rock series were generated in the faulted granitoidmagma belt. The parent magma of several rock series formed earliest originated from the lower crust ofgranulite facies; following the increase of geothermal temperature the source magma would migrate into themiddle crust of amphibolite facies. In the diapiric granitoid magma belt, the granitoid magma was formed firstin granitic layer of the upper crust, and then in the middle crust. In each subcycle the generation of magmastarted with the generation of more mafic one and finished with low eutectic one; they were formed in the formof layered melting in a particular position of the crust.

    • Geochemistry of a Rapakivi Granite Suite in a Proterozoic Rift Trough in Beijing and Its Vicinity

      1991, 65(2).

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      Abstract:Controlled by E-W-trending faults, a Proterozoic (1.4-1.8 Ga old) rapakivi granite suite was intruded inBeijing and the area to its east (within Hebei Province), forming three parallel belts of igneous rocks. Theisotopic, trace element and rare earth element geochemical data of a bimodal rock association made up ofanorthosite, gabbro and alkali basalt and olivine-bearing quartz-syenite, rapakivi granite and trachyte as wellas potassic A-type granites and anorogenic granites—— all suggest that there exists an incipient rift in thestudy area. Fractional crystallization of a mixed magma formed by the magma derived from the upper mantleand the magma derived by small degrees of fusion of the lower crust produced anorthosite cumulates. Thewater-deficient granitic magma was differentiated into a subalkaline series. When the fractional crystallizationwas incomplete, rhythmic eruptions took place.

    • Preliminary Study of the Characteristics and Genesis of Arsenate Minerals in the Oxidized Zone of the Debao Skarn-Type Cu-Sn Ore Deposit in Guangxi

      1991, 65(2).

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      Abstract:Through the study of the oxidized zone of the Debao skarn-type Cu-Sn deposit in Guangxi, the authorshave found 14 arsenate minerals, most of which are for the first time reported in China. They are mainly Cuarsenate minerals with subordinate Cu-Pb arsenate minerals and minor Fe-Pb-Ba varieties. Based on their paragenesis these minerals may be divided into the following series: (1) the clinoclasite-olivenite-cornwallite- cornubite- debaoite- copper silicarsenate association, (2) the scorodite- carminite- beudan-tite-bayldonite- duftite association, and (3) the scorodite-Ba-bearing pharmacosiderite- dussertite association. Arsenate minerals are formed generally in the oxidized zone of the sulfide-type deposits which lie in thewarm, humid and rainy torrid-subtropical zone with pH=6-8 and contain large amounts of arsenopyrite andcarbonate rocks.

    • The Thermal Structure of the Upper Mantle in Eastern China——Inferred from the Petrological Model

      1991, 65(2).

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      Abstract:Cenozoic basalt in eastern China contains abundant ultramafic xenoliths which are specimens of pyrolitesreleased during basaltic magma eruption. A total of 405 P-T data of pyroxene in the ultramafic rocks have beencollected, which present a more precise pyroxene geotherm. The average geothermal gradient in the upper man-tle represented by the pyroxene geotherm is about 3.3℃ / km, which is much less than that derived from theconductive thermal model (≈14℃ / km), implying the great significance of convective heat transfer. The calcu-lation shows that the contributions of convective and conductive heat transfers are 79% and 21%, respectively.The perturbation in the thermal structure of the upper mantle is an important manifestation of thetectonothermal event of Cenozoic continental rifting and intense basaltic volcanism in eastern China. Based onthe pyroxene geotherm and its comparison with the current geothermal field derived from the measurements ofthe surface heat flows, it is suggested that the Moho may be a secondary thermal boundary. The currentgeothermal field and the thermal structure of the lithosphere in eastern China may mainly reflect the result ofthe tectonothermal disturbance in the Neogene-Quaternary, in other words, the lithosphere has just begun toCool.

    • Origin, Evolution and Mechanism of the Jehol Fauna

      1991, 65(2).

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      Abstract:This paper deals with the geographic distribution and geological setting of the Jehol (northeastHebei-southwest Liaoning-southeast Inner Mongolia) fauna, and discusses the origination and the evolution ofits major biological groups. It is demonstrated that the Yan-Liao (northern Hebei-western Liaoning) area is theprovenance for the fauna. Why the fauna originated and developed in the area was intimately related to suchfactors as the palaeoclimate, palaeogeography, crustal movement, volcanism and frequent reversals of magnet-ic polarity at that time, in addition to the internal factors of the organisms themselves.

    • Redetermination of the Crystal Structure of Vesignieite

      1991, 65(2).

      Abstract (1145) HTML (0) PDF 0.00 Byte (81) Comment (0) Favorites

      Abstract:Vesignieite, Cu_3Ba(VO_4)_2(OH)_2, crystallizes in space group C_2 / m with a°=1.0270(2), b°=0.5911(1),c°=0.7711(2)nm and β=116.42(3)°. The intensity data were collected with the RIGAKU RASA-IISsingle-crystal four-circle diffractometer. The structure was determined by Patterson and Fourier methods andrefined by the least-square technique to a final R index of 0.051 for 614 independent diffraction points with|F? |>3σ|F?|. The crystal structure analysis shows that vesignieite has a layer structure parallel to (001). The powder diffraction lines were reindexed.

Chief Editor:HOU Zengqian

Governing Body:China Association for Science and Technology

Organizer:Geological Society of China

start publication :1922

ISSN:ISSN 1000-9515

CN:CN 11-2001/P

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