Geodynamic evolution of Central Asia in the Paleozoic and Mesozoic   总被引：18，自引：0，他引：18  

Wenjiao Xiao  Alfred Kröner  Brian Windley 《International Journal of Earth Sciences》2009,98(6):1185-1188

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Tectonic facies and the archipelago-accretion process of the West Kunlun,China     

Xiao  Wenjiao  Hou  Quanlin  Li  Jiliang  Brian F.  Windley  Hao  Jie  Fang  Aiming  Zhou  Hui  Wang  Zhihong  Chen  Hanlin  Zhang  Guocheng  Yuan  Chao 《中国科学:地球科学(英文版)》2000,43(1):134-143

A tectonic facies investigation carried out in the West Kunlun, China allows us to have worked out a tectonic model of orogen. The tectonic facies, from the north to the south, are composed of the following: 1. Southern Tarim tectonic realm; 2. North Kudi magmatic arc; 3. Kudi mélange; 4. Kudi micro-continent; 5. main shear zone; 6. Xianan Bridge calc alkaline complex; 7. Mazar-Kangxiwar mélange-accretion complex; and 8. Tianshuihai foreland fold-thrust belt. The tectonic facies 1»5 recorded the history of the northward subduction of the Prototethys and southward accretion of Eurasia in the Late Proterozoic-Early Paleozoic time, while the tectonic facies 6»8 recorded the history of the northward subduction of the Paleotethys and southward accretion of Eurasia in the Late Paleozoic-Early Mesozoic time, that of the tectonic evolution of the passive margin of the Qiangtang block, and that of the docking, and the final amalgamation of the Qiangtang block to the Eurasian continent. The tectonic facies investigation has indicated that a complicated archipelago-accretion orogenesis took place in the West Kunlun orogen, which was the important character of southward growth of the Eurasian continent.

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Geochemistry and petrogenesis of Archaean metavolcanic amphibolites from Fiskenaesset,S. W. Greenland     

Barry L. Weaver  John Tarney  Brian F. Windley  Bernard E. Leake 《Geochimica et cosmochimica acta》1982,46(11):2203-2215

The meta-volcanic amphibolites closely associated with the Fiskenaesset anorthosite complex can be subdivided on the basis of trace element patterns or mineral chemistry; by far the most abundant type has light rare-earth element (LREE) depleted REE patterns and displays a wide range in trace element abundances. Chemically comparable amphibolites can be recognised throughout the ca. 2800 M.yr. West Greenland terrain.The geochemistry of the basaltic amphibolites is dominantly controlled by fractional crystallisation processes, although variable degrees of partial melting may also be important. The required crystal extract (plagioclase dominated) in the proposed fractionation scheme is very similar to the primary mineralogy of cumulates of the Fiskenaesset complex and trace element models support a genetic relationship between the anorthosite complex and enclosing host amphibolites.The application of trace element discrimination to assign tectonic environment in the Archaean is arguable. However, details of the trace element chemistry (especially chondritic La/Ta ratios) are taken to suggest, out of a range of likely tectonic environments, an ocean floor, rather than island arc, affinity for the Fiskenaesset amphibolites. The large ion lithophile (LIL) elements display erratic distribution patterns, but are generally enriched relative to the REE. This appears not to be related to high-grade metamorphism but may be a relict feature of seafloor alteration. The association of the cumulate sequence with meta-volcanic amphibolites and metasediments probably represents an ocean floor assemblage emplaced into the lower crust during crustal accretion.  相似文献   

Petrochemistry and mineralogy of early Precambrian anorthositic rocks of the Limpopo belt, southern Africa     

A.K. Hor  D.K. Hutt  J.V. Smith  J. Wakefield  B.F. Windley 《Lithos》1975,8(4):297-310

Two sections of the anorthosite ‘complex’ were examined at Messina, South Africa and at Pikwe, Botswana. Thirty XRF whole-rock analyses of samples in stratigraphic order show that alkalies at Messina increase upwards from leuco-gabbros to anorthosites, but no such correlation was found at Pikwe. Electron probe analyses of plagioclases in 33 samples indicate extensive normal zoning and variation (An₃₁-An₈₀) especially at Pikwe. The highest An-contents tend to vary monotonically with stratigraphic position, whereas the lowest values are erratic. Twenty-two amphibole analyses indicate that SiO₂, TiO₂ and MgO/FeO increase, decrease and increase, respectively, with height at Messina, but 22 analyses from Pikwe show no such trends. Their compositions are similar to those from the Fiskenaesset complex. Aluminous chromites are Fe-rich, also like the Fiskenaesset ones.

The Limpopo anorthositic rocks belong to a layered igneous body that was recrystallized by regional metamorphism and subjected to erratic metasomatism. The original Limpopo and Fiskenaesset bodies strongly resemble gabbroic and peridotitic relics in the Peninsular Ranges Batholith in S. California.  相似文献   

Precambrian tectonics illustrated : A. Kröner and R. Greiling (editors). Schweizerbart, Stuttgart, 1984, viii + 419 pp, 317 figs., 13 tables (paperback)     

Brian F. Windley 《Tectonophysics》1985,117(3-4)

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Sapphirine/kornenipine-bearing rocks and crustal uplift history of the Limpopo belt,Southern Africa     

B. F. Windley  D. Ackermand  R. K. Herd 《Contributions to Mineralogy and Petrology》1984,86(4):342-358

Sapphirine/kornerupine-bearing rocks occur within the anorthosites of the Messina layered intrusion in the Limpopo mobile belt of Zimbabwe. The X_Mg range of the major minerals is as follows: cordierite (0.98-0.93); enstatite (0.97-0.86); chlorite (0.98-0.92); phlogopite (0.98-0.90); sapphirine (0.98-0.86); kornerupine (0.94-0.88); gedrite (0.96-0.85); spinel (0.92-0.78). There are four rock types, the constituent minerals of which have different values, which decrease in the above mineral order; other minerals are corundum, sillimanite and relict kyanite. We recognise twenty reactions without phlogopite and nine reactions involving phlogopite. The textural relations and the plots of the microprobe data of coexisting minerals in the MgO-Al₂O₃-SiO₂-(H₂O) system are consistent with the following sequence of main reactions: (1) enstatite+corundum cordierite+sapphirine; (4) sapphirine+sillimanite cordierite+corundum; (8) kornerupine+corundum cordierite+sapphirine; (13) kornerupine cordierite+sapphirine+enstatite; (15) enstatite+spinel chlorite+sapphirine; (18) cordierite+sapphirine chlorite+corundum; (20) sapphirine chlorite+corundum+spinel. The early reactions are shown by coarse-grained reaction intergrowths, kornerupine and gedrite breakdown is shown by finer-grained symplectites, and the latest reactions by very fine-grained products in micro-fractures. These selected reactions illustrate a remarkably steep trajectory from thePT peak close to 10 kbar and 800° C to the minimum observable at 3.5–4.5 kbar and 700° C as indicated by the pure MASH system. Very rapid uplift took place under nearly isothermal conditions. The protolith of this material was possibly sedimentary, derived from altered volcanic rocks. The bulk composition is close to the composition of kornerupine or to a mixture of alunite, chlorite and pyrophyllite. These texturally and mineralogically complex rocks contain a wealth of relevant data for documenting crustal uplift history.  相似文献   

Högbomite in migmatitic paragneiss in the Betroka shear belt, Vohidava area, Precambrian of southern Madagascar     

T. Razakamanana  D. Ackermand  B. F. Windley 《Mineralogy and Petrology》2000,68(4):257-269

Summary ?The Betroka sinistral shear belt is a major geotectonic unit in the Precambrian of southern Madagascar. It consists of migmatitic paragneiss commonly interlayered with phlogopite-bearing diopsidite, phlogopite-humite-diopside-spinel marble, sillimanite-garnet quartzite and syn-tectonic S-type leucogranite. H?gbomite occurs sporadically in the migmatitic paragneiss in patches of magnetite with hercynite, and at the border of magnetite where it is in contact with hercynite, rare ilmenite, rutile and cordierite, which contains a network of chlorite, pyrophyllite and rare corundum/diaspore. X_Mg = Mg/(Mg + Fe) decreases as follows: Crd > Bt > Chl > H?g > Hc. The textural relations suggest the following h?gbomite-participating reactions: Ti-bearing hercynite ↠ hercynite + h?gbomite (intergrown/exsolution lamellae) ilmenite + cordierite ↠ hercynite + h?gbomite + rutile + chlorite/pyrophyllite   h?gbomite ↠ hercynite + ilmenite + corundum The chemical composition of h?gbomite varies substantially from grain to grain in individual samples and from sample to sample, this variation being highly dependent on the associated minerals. There is a weak zoning from core to rim in individual grains intergrown with hercynite and also in grains at the margin of hercynite, but this zoning is overprinted by zones formed at grain rims depending on the surrounding phases. In contact with hercynite, h?gbomite has FeO (total Fe as FeO) 27.1–28.5 wt.%, and MgO 4.5–5.8 wt.%, and in contact with magnetite FeO 24.9–26.5 wt.%, and MgO 6.0–8.5 wt.% and the core contents are within these values. TiO₂7.5–4.0 wt.% and Al₂O₃62.0–59.0 wt.% show zonations with increase from core to rim. Estimated P-T conditions are 6.0 ± 1.0 kbar and 700 ± 100 °C reached during a peak metamorphic stage of the Pan-African orogeny. However, the presence of diaspore with exsolved hercynite-magnetite indicates extreme retrograde metamorphism in the decompressional central part of this shear belt of southern Madagascar.

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Zusammenfassung ?H?gbomit in migmatitischem Paragneis von Vohidava in der Betroka Scherzone im südlichen Pr?kambrium von Madagaskar Die sinistrale Betroka Scherzone ist eine ausgepr?gte tektonische Einheit des Pr?kambriums in Süd Madagaskar. Sie besteht aus migmatitischem Paragneis, in dem Phlogopit-führender Diopsidit, Phlogopit-Humit-Diopsid-Spinell-Marmor, Sillimanit-Granat-Quarzit und syntektonischer S-Typ Granit eingelagert sind. Im migmatitischen Paragneis kommen sporadisch H?gbomit/Hercynit Nester im Magnetit vor und am Magnetitrand findet sich H?gbomit im Kontakt mit Hercynit und Cordierit, der mit einem Netzwerk aus Chlorit/Pyrophyllit gefüllt ist, sowie sporadisch mit Korund/Diaspor, Ilmenit und Rutil. X_Mg = Mg/(Mg + Fe) nimmt in folgender Reihung ab: Crd > Bt > Chl > H?g > Hc. Aus den texturellen Beziehungen werden folgende H?gbomit-partizipierende Reaktionen abgeleitet: Ti-führender Hercynit ↠ Hercynit + H?gbomit (verwachsen/Entmischungslamellen)   H?gbomit ↠ Hercynit + Ilmenit + Korund Die chemische Zusammensetzung von H?gbomit variiert betr?chtlich von Korn zu Korn in einer Probe und von Probe zu Probe; wobei die Variation von den Kontaktmineralen abh?ngt. H?gbomit im Hercynit hat eine schwache Zonierung von Kern zum Rand. Im H?gbomit am Hercynitrand ist die Kern-Rand-Zonierung durch die von den Kontaktmineralen abh?ngige Randzusammensetzung überpr?gt. Im Kontakt zum Hercynit hat H?gbomit 27,1–28,5 Gew.% FeO (total Fe als FeO) und 4,5–5,8 Gew.% MgO und im Kontakt zu Magnetit 24,9–26,5 Gew.% FeO und 6,0–8,5 Gew.% MgO, die Kernzusammensetzung liegt zwischen den beiden Randwerten. TiO₂nimmt vom Kern zu den R?ndern von 7,5 bis 4,0 Gew.% ab und Al₂O₃von 62,0 bis 59,0 Gew.%. Die P-T Bedingungen des Metamorphose-Peaks w?hrend der Pan-Afrikanischen Orogenese erreichten 6,0 ± 1,0 Kbar und 700 ± 100 °C. Die sp?te Bildung von Diaspor und die Hercynit-Magnetit-Entmischung weisen auf eine tiefgreifende retrograde Metamorphose im Dekompressions-Zentralbereich der Betroka-Scherzone im südlichen Madagaskar hin.

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Received January 15, 1999;/revised version accepted July 6, 1999  相似文献   

The Ediacaran radiogenic Sr isotope excursion in the Doushantuo Formation in the Three Gorges area,South China     

Yusuke Sawaki  Takeshi Ohno  Miyuki Tahata  Tsuyoshi Komiya  Takafumi Hirata  Shigenori Maruyama  Brian F. Windley  Jian Han  Degan Shu  Yong Li 《Precambrian Research》2010,176(1-4):46-64

The Ediacaran period was one of the most important times for the evolution of life. However, the scarcity of well-preserved outcrops of Ediacaran rocks still leaves ambiguity in decoding ambient surface environmental changes and biological evolution.The Ediacaran strata in South China are almost continuously exposed, comprise mainly carbonate rocks with subordinate black shales and sandstones, and they contain many fossils, suitable for study of environmental and biological changes in the Ediacaran. We conducted drilling through the Doushantuo Fm at four sites in the Three Gorges area to obtain continuous, fresh samples without surface alteration and oxidation. We analyzed ⁸⁷Sr/⁸⁶Sr and ⁸⁸Sr/⁸⁶Sr ratios of the fresh carbonate rocks, selected on the basis of microscopic observations and the geochemical signatures of Sr contents, Mn/Sr and Rb/Sr ratios, and δ¹⁸O values, with a multiple collector-inductively coupled plasma-mass spectrometer (MC-ICP-MS).The chemostratigraphy of the ⁸⁷Sr/⁸⁶Sr ratios of the drilled samples displays a smooth curve and two large positive shifts during Ediacaran time. The combination of the detailed chemostratigraphies of δ¹³C, δ¹⁸O and ⁸⁷Sr/⁸⁶Sr values and Mn and Fe contents enables us to decode the surface environmental changes and their causes in the Ediacaran. The first large positive excursion of ⁸⁷Sr/⁸⁶Sr occurred together with negative δ¹³C and positive δ¹⁸O excursions. The higher ⁸⁷Sr/⁸⁶Sr values indicate an enhancement of continental weathering, whereas the positive δ¹⁸O excursion suggests global cooling. Global regression due to global cooling enhanced the oxidative decay of exposed marine organic sediments and continental weathering. Accelerated influx of nutrients promoted primary productivity, resulting in oxidation of dissolved organic carbon (DOC), whereas active sulfate reduction due to a higher sulfate influx from the continents caused remineralization of the large DOC, both of which caused a negative δ¹³C anomaly. The 580 Ma Gaskiers glaciation accounts for the close correlation among the positive ⁸⁷Sr/⁸⁶Sr, negative δ¹³C and positive δ¹⁸O excursions.The second large positive shift of ⁸⁷Sr/⁸⁶Sr firstly accompanied a positive δ¹³C excursion, and continued through the Shuram δ¹³C negative excursion. The positive correlation of δ¹³C and ⁸⁷Sr/⁸⁶Sr values is consistent with an enhanced continental weathering rate due to continental collisions that built Trans-Gondwana mountain chains, and with a higher primary activity due to the enhancement of continental weathering and consequent higher nutrient contents in seawater. The accompanied increase in Mn and Fe contents implies a gradual decline of the seawater oxygen content due to more active aerobic respiration and oxidation of reductive materials flowing in the oceans. In the Shuram excursion, higher ⁸⁷Sr/⁸⁶Sr values and a transition from increase to decrease in Mn and Fe contents were accompanied by the large negative δ¹³C excursion. The higher ⁸⁷Sr/⁸⁶Sr values are the first compelling evidence for enhanced continental weathering, which was responsible for the large δ¹³C anomaly through the remineralization of the DOC by more active sulfate reduction due to a higher sulfate influx. Higher Mn and Fe contents in the early and middle stages of the excursion suggest a decline in the oxygen content of seawater due to oxidative decay of the DOC, whereas in the late stages the decrease in Mn and Fe contents is consistent with oceanic oxygenation.The emergence of Ediacara biota after the Gaskiers glaciation and the prosperity of the latest Ediacaran is concomitant with the formation of more radiogenic seawater with high ⁸⁷Sr/⁸⁶Sr values, suggesting that enhanced continental weathering, and the consequent higher influx of nutrients, played an important role in biological evolution.  相似文献   

New Zircon Ages for Precambrian Granites, Gneisses and Granulites from Central and Southern Madagascar: Significance for Correlations in East Gondwana     

A. Krner  B.F. Windley  P. Jaecke  A.S. Collins  T.S. Brewer  A. Nemchin  T. Razakamanana 《Gondwana Research》1999,2(3):351

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Relic permafrost structures in the Gobi of Mongolia: age and significance     

Lewis A. Owen  Ben Richards  Edward J. Rhodes  W. Dickson Cunningham  Brian F. Windley  J. Badamgarav  D. Dorjnamjaa 《第四纪科学杂志》1998,13(6):539-547

Relict permafrost structures (ice-wedge casts and cryoturbation structures) are present in the Gobi of southern Mongolia. Luminescence dates of sediments are presented to constrain the age of formation of permafrost structures. These data show that there was a phase of permafrost development during the latter part of the Last Glacial (after about 22 to 15 ka) that resulted in cryoturbated sediments and ice-wedge casts. Furthermore, permafrost degradation occurred during late Pleistocene times (13–10 ka) and was absent during the early Holocene. These permafrost structures mark the southernmost evidence of permafrost in northern Asia during late Quaternary times and indicate that the mean annual air temperature was below approximately −6°C during their formation. © 1998 John Wiley & Sons, Ltd.  相似文献