Geochemistry and P-T-t evolution of the Abu-Barqa Metamorphic Suite, SW Jordan, and implications for the tectonics of the northern Arabian-Nubian Shield

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• 作者：Ghaleb H. Jarrar ; Thomas Theye ; Najel Yaseen ; Martin Whitehouse ; Victoria Pease ; Cees Passchier
• 关键词：Arabian&ndash ; Nubian Shield ; Metapelitic rocks ; Thermobarometry ; Pseudosections ; Geochronology ; Dead Sea Transform
• 刊名：Precambrian Research
• 出版年：December, 2013
• 年：2013
• 卷：239
• 期：Complete
• 页码：56-78
• 全文大小：12063 K

文摘

The Abu Barqa Metamorphic Suite (ABMS) represents the oldest part of the Arabian-Nubian Shield in southern Jordan. It comprises tonalitic gneiss, metasediments including schist and paragneiss, and granitic gneiss, intruded by later granitic bodies. Geochemically, the majority of the schist samples have shale and Fe-shale protoliths, while the paragneisses represent metagreywacke. Tectonic discrimination diagrams indicate that the protolith of the ABMS was deposited at an active continental margin/island arc setting.

U-Pb zircon (SIMS) ages from metamorphic and igneous rocks of the ABMS indicate that it evolved between 鈭?00 and 鈭?10 Ma. A tonalitic gneiss has a crystallization age of 787 卤 3 Ma. Detrital zircon from the metasediment has a range of concordant ages from 680 to 860 Ma. The entire metamorphic complex was intruded by calc-alkaline granitoids (鈭?15-610 Ma) and quartz diorite dated (鈭?00 Ma).

Field and petrographic investigations of ABMS metasediment elucidate the development of three metamorphic zones, from north to south: (1) andalusite-staurolite (andalusite + staurolite + biotite + muscovite + plagioclase 卤 garnet + quartz 卤 chlorite + fibrolitic sillimanite + accessories), (2) garnetsillimanite (sillimanite + garnet + biotite + plagioclase + quartz + K-feldspar + cordierite (pinitized) 卤 rutile 卤 ilmenite), and (3) cordierite-sillimanite (sillimanite + biotite + plagioclase + cordierite + hercynite + quartz + accessories).

The maximum metamorphic conditions (M1) were attained in the garnet-sillimanite zone (5-6 kbar, 鈭?00 掳C), while peak conditions of 鈭?.2 kbar and 540 掳C were obtained for the andalusite-staurolite zone (using both forward-pseudosection modeling and inverse-modeling with multi-equilibrium approach). Compositional isopleth calculations of small relics of garnet yield about 3.5 kbar and 600 掳C for the sillimanite-cordierite zone. These values are in agreement with results obtained by TWQ inverse modeling. The M1 event most probably occurred around 鈭?25 and was followed by a decompressional thermal phase (M2) contemporaneous with post-tectonic granitoid emplacement at 鈭?15-610 Ma; and lastly went through a retrograde cooling phase (M3) accompanying uplift of the whole complex to the surface at 鈭?05 Ma.