The occurrence of high-pressure mafic-ultramafic bodies within major shear zones is one of the in... more The occurrence of high-pressure mafic-ultramafic bodies within major shear zones is one of the indicators of paleo-subduction. In mafic granulites of the Andriamena complex (north-eastern Madagascar) we document unusual textures including garnet-clinopyroxene-quartz coronas that formed after the breakdown of orthopyroxene-plagioclase-ilmenite. Textural evidence and isochemical phase diagram calculations in the Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O-TiO2 system indicate a pressure-temperature (P-T) evolution from an isothermal (780 degrees C) pressure up to c. 24 kbar to decompression and cooling. Such a P-T trajectory is typically attained in a subduction zone setting where a gabbroic/ultramafic complex is subducted and later exhumed to the present crustal level during oceanic closure and final continental collision. The present results suggest that the presence of such deeply subducted rocks of the Andriamena complex is related to formation of the Betsimisaraka suture. LA-ICPMS U-Pb zircon dating of pelitic gneisses from the Betsimisaraka suture yields low Th/U ratios and protolith ages ranging from 2535 to 2625 Ma. A granitic gneiss from the Alaotra complex yields a zircon crystallization age of ca. 818 Ma and Th/U ratios vary from 1.08 to 2.09. K-Ar dating of muscovite and biotite from biotite-kyanite-sillimanite gneiss and garnet-biotite gneiss yields age of 486 +/- 9 Ma and 459 +/- 9 Ma respectively. We have estimated regional crustal thicknesses in NE Madagascar using a flexural inversion technique, which indicates the presence of an anomalously thick crust (c. 43 km) beneath the Antananarivo block. This result is consistent with the present concept that subduction beneath the Antananarivo block resulted in a more competent and thicker crust. The textural data, thermodynamic model, and geophysical evidence together provide a new insight to the subduction history, crustal thickening and evolution of the high-pressure Andriamena complex and its link to the terminal formation of the Betsimisaraka suture in north-eastern Madagascar. (C) 2015 Elsevier B.V. All rights reserved.
... the first detailed geological transect across the Mongolian Western Altai using modern method... more ... the first detailed geological transect across the Mongolian Western Altai using modern methods of structural geology and fault ... Windley, D. Dorjnamjaa, G. Badamgarov, and M. Saandar (1996), A structural transect across the Mongolian Western Altai ... American Geophysical Union ...
... Universität Mainz, 55099 Mainz, Germany 4 United Institute of Geology, Geophysics and Mineral... more ... Universität Mainz, 55099 Mainz, Germany 4 United Institute of Geology, Geophysics and Mineralogy, Siberian Branch of the Russian Academy of Sciences, 3 Koptyug Pr., Novosibirsk 630090, Russia 5 Institute of Geology and Mineral Resources, Mongolian Academy of ...
Page 1. Geology doi: 10.1130/0091-7613(1996)024<0131:EPGTAP&am... more Page 1. Geology doi: 10.1130/0091-7613(1996)024<0131:EPGTAP>2.3.CO;2 1996;24;131-134 Geology Brian F. Windley, Martin J. Whitehouse and Mahfood AO Ba-Bttat accretion of the eastern Arabian Shield Early Precambrian ...
Sapphirine/kornerupine-bearing rocks occur within the anorthosites of the Messina layered intrusi... more 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 ( ...
The eastern Tiklik belt is mainly composed of meta-sedimentary rocks of the Ailiankate and Sailaj... more The eastern Tiklik belt is mainly composed of meta-sedimentary rocks of the Ailiankate and Sailajiazitage Groups that were previously interpreted as Palaeoproterozoic, Mesoproterozic and Neoproterozoic stratigraphic units, which are part of the Tarim Precambrian basement. Our new detrital (U-Pb) zircon ages yield a dominant single peak with a major range between ca. 700 Ma and 800 Ma for meta-sedimentary rocks from both the Ailiankate and Sailajiazitage Groups, which demonstrates that they were mainly derived from an independent Neoproterozoic terrane. There are several ages of 444–659 Ma, of which, the youngest has an age of 444 ± 6 Ma, indicating that the time of deposition of the meta-sedimentary rocks could have been in the Early Silurian. The porphyritic granite sample has a weighted mean crystallization age of 442 ± 2 Ma. The adakite-like geochemical characteristics of the porphytitic granite suggest derivation from the melting of the oceanic slab and formation in a subduction...
The occurrence of high-pressure mafic-ultramafic bodies within major shear zones is one of the in... more The occurrence of high-pressure mafic-ultramafic bodies within major shear zones is one of the indicators of paleo-subduction. In mafic granulites of the Andriamena complex (north-eastern Madagascar) we document unusual textures including garnet-clinopyroxene-quartz coronas that formed after the breakdown of orthopyroxene-plagioclase-ilmenite. Textural evidence and isochemical phase diagram calculations in the Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O-TiO2 system indicate a pressure-temperature (P-T) evolution from an isothermal (780 degrees C) pressure up to c. 24 kbar to decompression and cooling. Such a P-T trajectory is typically attained in a subduction zone setting where a gabbroic/ultramafic complex is subducted and later exhumed to the present crustal level during oceanic closure and final continental collision. The present results suggest that the presence of such deeply subducted rocks of the Andriamena complex is related to formation of the Betsimisaraka suture. LA-ICPMS U-Pb zircon dating of pelitic gneisses from the Betsimisaraka suture yields low Th/U ratios and protolith ages ranging from 2535 to 2625 Ma. A granitic gneiss from the Alaotra complex yields a zircon crystallization age of ca. 818 Ma and Th/U ratios vary from 1.08 to 2.09. K-Ar dating of muscovite and biotite from biotite-kyanite-sillimanite gneiss and garnet-biotite gneiss yields age of 486 +/- 9 Ma and 459 +/- 9 Ma respectively. We have estimated regional crustal thicknesses in NE Madagascar using a flexural inversion technique, which indicates the presence of an anomalously thick crust (c. 43 km) beneath the Antananarivo block. This result is consistent with the present concept that subduction beneath the Antananarivo block resulted in a more competent and thicker crust. The textural data, thermodynamic model, and geophysical evidence together provide a new insight to the subduction history, crustal thickening and evolution of the high-pressure Andriamena complex and its link to the terminal formation of the Betsimisaraka suture in north-eastern Madagascar. (C) 2015 Elsevier B.V. All rights reserved.
... the first detailed geological transect across the Mongolian Western Altai using modern method... more ... the first detailed geological transect across the Mongolian Western Altai using modern methods of structural geology and fault ... Windley, D. Dorjnamjaa, G. Badamgarov, and M. Saandar (1996), A structural transect across the Mongolian Western Altai ... American Geophysical Union ...
... Universität Mainz, 55099 Mainz, Germany 4 United Institute of Geology, Geophysics and Mineral... more ... Universität Mainz, 55099 Mainz, Germany 4 United Institute of Geology, Geophysics and Mineralogy, Siberian Branch of the Russian Academy of Sciences, 3 Koptyug Pr., Novosibirsk 630090, Russia 5 Institute of Geology and Mineral Resources, Mongolian Academy of ...
Page 1. Geology doi: 10.1130/0091-7613(1996)024<0131:EPGTAP&am... more Page 1. Geology doi: 10.1130/0091-7613(1996)024<0131:EPGTAP>2.3.CO;2 1996;24;131-134 Geology Brian F. Windley, Martin J. Whitehouse and Mahfood AO Ba-Bttat accretion of the eastern Arabian Shield Early Precambrian ...
Sapphirine/kornerupine-bearing rocks occur within the anorthosites of the Messina layered intrusi... more 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 ( ...
The eastern Tiklik belt is mainly composed of meta-sedimentary rocks of the Ailiankate and Sailaj... more The eastern Tiklik belt is mainly composed of meta-sedimentary rocks of the Ailiankate and Sailajiazitage Groups that were previously interpreted as Palaeoproterozoic, Mesoproterozic and Neoproterozoic stratigraphic units, which are part of the Tarim Precambrian basement. Our new detrital (U-Pb) zircon ages yield a dominant single peak with a major range between ca. 700 Ma and 800 Ma for meta-sedimentary rocks from both the Ailiankate and Sailajiazitage Groups, which demonstrates that they were mainly derived from an independent Neoproterozoic terrane. There are several ages of 444–659 Ma, of which, the youngest has an age of 444 ± 6 Ma, indicating that the time of deposition of the meta-sedimentary rocks could have been in the Early Silurian. The porphyritic granite sample has a weighted mean crystallization age of 442 ± 2 Ma. The adakite-like geochemical characteristics of the porphytitic granite suggest derivation from the melting of the oceanic slab and formation in a subduction...
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