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Late Neoproterozoic adakitic magmatism of the eastern Arabian Nubian Shield

Geoscience Frontiers 2019年第6期10卷 1981-1992页

作者： Grant M.Cox john foden Alan S.Collins Centre for Tectonics Resources and Exploration(TRaX) Dept of Earth SciencesThe University of Adelaide

Late Neoproterozoic adakitic magmatism within the Eastern Arabian Nubian Shield has been dated at633.2±9.0 Ma(2σ).These magnas intrude the forearc Ad Dawadimi Basin,which is composed of metapelitic schists and greywacke along with ophiolitic melanges of boninitic affinity which underwent inversion and deformation by^620 *** adakitic magmatism,while intruding parts of the Ad Dawadimi Basin,predates this deformation,but is possibly coincident with basin *** adakitic magmatism requires melting of an amphibolite or eclogitic source,empirical and experimental constraints require anomalously hot supra-subduction zone *** that this magmatism immediately predates basin inversion,these magmas possibly pinpoint the timing of the slab breaking,marking the terminal stages of arc magmatism,terrane accretion and the influx of hot oceanic asthenospheric *** influx of hot asthenospheric mantle may also be responsible for postcolltsional A-type magmatism.

关键词： Arabian Nubian Shield Adakites A-type magmatism

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Petrogenesis of the Late Cretaceous Tholeiitic Volcanism and Oceanic Island Arc Affinity of the Chagai Arc, Western Pakistan

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Acta Geologica Sinica(English Edition) 2017年第4期91卷 1248-1263页

作者： Rehanul Haq SIDDIQUI M. Qasim JAN Mohammad Asif KHAN M. Ishaq KAKAR john D. foden Baluchistan University of Information Technology Engineering and Management Sciences Quetta Pakistan National Centre of Excellence in Geology University of Peshawar Peshawar & COMSTECH Islamabad Pakistan Karakoram International University Gilgit Pakistan Centre of Excellence in Mineralogy University of Baluchistan Quetta Pakistan Department of Earth Sciences University of Adelaide SA 5005 Australia

The Late Cretaceous Chagai arc outcrops in western Pakistan, southern Afghanistan and eastern Iran. It is in the Tethyan convergence zone, formed by northward subduction of the Arabian oceanic plate beneath the Afghan block. The oldest unit of the Chagai arc is the Late Cretaceous Sinjrani Volcanic Group. This is composed of porphyritic lava flows and volcaniclastic rocks, and subordinate shale, sandstone, limestone and chert. The flows are fractionated low-K tholeiitic basalts, basaltic- andesites, and andesites. Relative enrichment in their LILE and depletion in HFSE, and negative Nb and Ta and positive K, Ba and Sr anomalies point to a subduction-related origin. Compared to MORB, the least fractionated Chagai basalts have low Na2O, Fe2O3^T, CaO, Ti, Zr, Y and ^87Sr/^86Sr. Rather than an Andean setting, these results suggest derivation from a highly depleted mantle in an intraoceanic arc formed by Late Cretaceous convergence in the Ceno-Tethys. The segmented subduction zone formed between Gondwana and a collage of small continental blocks （Iran, Afghan, Karakoram, Lhasa and Burma） was accompanied by a chain of oceanic island arcs and suprasubduction ophiolites including Semail, Zagros, Chagai-Raskoh, Kandahar, Muslim Bagh, Waziristan and Kohistan-Ladakh, Nidar, Nagaland and Manipur. These complexes accreted to the southern margin of Eurasia in the Late Cretaceous.

关键词： Chagai arc tholeiitic volcanics Late Cretaceous western Pakistan

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Late syn-to post-collisional magmatism in Madagascar:The genesis of the Ambalavao and Maevarano Suites

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Geoscience Frontiers 2019年第6期10卷 2063-2084页

作者： Donnelly B.Archibald Alan S.Collins john D.foden Justin L.Payne Peter Holden Théodore Razakamanana Department of Earth Sciences St.Francis Xavier UniversityPhysical Sciences Complex5009 Chapel SquareAntigonishNSB2G 2W5Canada Centre for Tectonics Resources and Exploration(TRaX)Department of Earth SciencesThe University of AdelaideAdelaide 5005SAAustralia Centre for Tectonics Resources and Exploration(TRaX)School of Built and Natural EnvironmentsUniversity of South AustraliaMawson LakesSA5001Australia Research School of Earth Sciences The Australian National UniversityCanberraACT2601Australia Departement des Sciences de la Terre Universitede ToliaraToliara601Madagascar

The East African Orogen involves a collage of Proterozoic microcontinents and arc terranes that became wedged between older cratonic blocks during the assembly of *** Ediacaran-Cambrian Ambalavao and Maevarano Suites in Madagascar were emplaced during the waning orogenic stages and consist of weakly deformed to undeformed plutonic rocks and dykes of mainly porphyritic granite but also gabbro,diorite and charnockite.U-Pb geochronological data date emplacement of the Ambalavao Suite to between ca.580 Ma and 540 Ma and the Maevarano Suite to between ca.537 Ma and522 *** and trace element concentrations are consistent with emplacement in a syn-to postcollisional tectonic setting as A-type(anorogenic) ***(δ^(18)O of 5.27‰-7.45‰) and hafnium(ε(Hf)(t) of-27.8 to-12.3) isotopic data from plutons in the Itremo and Antananarivo Domains are consistent with incorporation of an ancient crustal *** primitive δ^(18)O(5.27‰-5.32‰) andε(Hf)(t)(+0.0 to+0.2) isotopic values recorded in samples collected from the Ikalamavony Domain demonstrate the isotopic variation of basement sources present in the Malagasy *** Hf isotopic composition of Malagasy zircon are unlike more juvenile Ediacaran-Cambrian zircon sou rces elsewhere in the East African Orogen and,as such,Madagascar represents a distinct and identifiable detrital zircon source region in Phanerozoic sedimentary provenance *** together,these data indicate that high-T crustal anatexis,crustal assimilation and interaction of crustal material with mantle-derived melts were the processes operating during magma *** magmatism was coeval with polyphase deformation throughout Madagascar during the amalgamation of Gondwana and magmatism is interpreted to reflect lithospheric delamination of an extensive orogenic plateau.

关键词： Madagascar geology East African orogen Zircon geochronology Zircon oxygen and hafnium isotopes Post-collisional magmatism

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Petrochemistry of Volcanic and Plutonic Rocks in Loei Province, Loei-Petchabun Fold Belt, Thailand

Petrochemistry of Volcanic and Plutonic Rocks in Loei Provin...

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第五届全国计算机数学学术会议

作者： Kamonporn Kromkhun Graham Baines Peangta Satarugsa john foden Geology and Geophysics School of Earth and Environmental Sciences University of Adelaide Geotechnology Department of Technology Khon Kaen University

The petrography and geochemistry of Permo-Triassic volcanic and plutonic rocks of the Loei-Phetchabun Fold Belt located in Amphoe Wang Sa Phung and Maung areas, Loei Province were *** intermediate igneous rocks have calc-alkaline affinities and are characterized by moderately fractionated LREEs and relatively flat HREEs with negative Eu anomalies. Both volcanic and plutonic samples display positive Rb, Th, Ce, Sm and Y anomalies and negative Nb and Ti anomalies. The geochemical data indicate that fractional crystallization of plagioclase, hornblende, biotite, titanite and apatite and/or magma mixing were important processes during the generation of these igneous rocks. Therefore, the data indicate magmatism at an east-dipping continent-ocean subduction zone where a former ocean between the Indochina and Sibumasu blocks was subducted beneath the Indochina block. Available geochronology data indicate that subduction was active from at least 244-230 Ma. The subduction-derived melts were probably contaminated by the overlying continental crust.

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