The Cryogenian Arc formation and successive High-K calc-alkaline plutons of Socotra Island (Yemen)
The Socotra Island belongs to the southern rifted margin of the Gulf of Aden and occupied in Neoproterozoic times a key position to constrain the age and the nature of the largely hidden Neoproterozoic rocks of the Arabian plate. Our integrated field, petrographic, geochemical and geochronological study in the Neoproterozoic rocks recognizes three main successive events: (1) high-temperature ductile deformation and metamorphism forming probably in a compressive or transpressive regime; (2) mafic to intermediate intrusions as vertical sheets, kilometre-scale gabbro laccoliths, mafic dike swarm and lavas which present mainly a depleted arc signature with some evidences of evolution from an enriched-arc signature; (3) felsic intrusions mainly composed of highly potassic calc-alkaline and pinkish granites dated between 840 and 780 Ma. Relationships between the various petrographic types and U–Pb data suggest that these events occurred during a relatively short time span (80 Ma at max.). Earlier HT-LP metamorphism stage as well as geochemical signature of mafic rocks show that development of Cryogenian formations of Socotra were controlled successively by an Andean-arc and a back-arc setting. These features cannot be easily reconciled with those of the Arabian-Nubian Shield to the west of Socotra and of the Mozambique Belt to the south. We propose that the Socotra basement was developed at an active margin close to the India block in Cryogenian times.
KeywordsNeoproterozoic East-African-Antartic-Orogen Arabian-Nubian Shield Socotra Island Andean-type arc Back-arc basin
We thank Ph. Olivier and L. Siebenaller for constructive discussions.
We also thank P. Barbey and I. Mercolli for their valuable remarks which helped us to improve a first version of this article.
- Al-Kathiri AFA 1998. Geology of the Crystalline Basement of the Hasik Region (Dhofar, Sultanate of Oman). MSc thesis, University of BerneGoogle Scholar
- Beydoun ZR, Bichan HR (1970) The geology of Socotra Island, Gulf of Aden. Quaterly J Soc Lond 25:413–446Google Scholar
- Cabanis B, Lecolle M (1989) Le diagramme La/10-Y/15-Nb/8; un outil pour la discrimination des series volcaniques et la mise en evidence des processus de melange et/ou de contamination crustale. CRAS Paris 309:2023–2029Google Scholar
- Gass G, Ries AC, Shackleton RM, Smewing JD (1990) Tectonics, geochronology and geochemistry of the Precambrian rocks of Oman. In: Robertson AHF, Searle MP, Ries AC (eds) The Geology and Tectonics of the Oman Region Spec Pub Geol Soc Lond 49: 585–599Google Scholar
- Johnson PR, Woldehaimanot B (2003) Development of the Arabian-Nubian shield: perspectives on accretion and deformation in the northern East African Orogen and the assembly of Gondwana. In: Yoshida M, Windley BF, Dasgupta S (eds) Proterozoic East Gondwana: Supercontinent Assembly and Breakup. Spec. Pub Geol Soc Lond 206: 289–325Google Scholar
- Jacobs J, Thomas RJ (2010) Himalayan-type indenter-escape tectonics model for the southern part of the late Neoproterozoic–early Paleozoic East African–Antarctic orogen. Geol Soc Am 32:721–724Google Scholar
- LeBas MJ, LeMaitre RW, Streckeisen A, Zanettin B (1986) A chemical classification of volcanic rocks based on the total alkali silica diagram. J Pet 27:745–750Google Scholar
- Leroy S, Gente P, Fournier M, d’Acremont E, Patriat P, Beslier M-O, Bellahsen N, Maia M, Blais A, Perrot J, Al-Kathiri A, Merkouriev S, Fleury JM, Ruellan PY, Lepvrier C, Huchon P (2004) From rifting to spreading in the eastern Gulf of Aden: a geophysical survey of a young oceanic basin from margin to margin. Terra Nova 16:185–192CrossRefGoogle Scholar
- Leroy S, Lucazeau F, d’Acremont E, Watremez L, Autin J, Rouzo S, Bellahsen N, Tiberi C, Ebinger C, Beslier M-O, Perrot J, Razin P, Rolandone F, Sloan H, Stuart G, Al-Lazki A, Al-Toubi K, Bache F, Bonneville A, Goutorbe B, Huchon P, Unternehr P, Khanbari K (2010a) Contrasted styles of rifting in the eastern Gulf of Aden: a combined wide-angle MCS and Heat flow survey. Geochem Geophys Geosyst 11(Q07004):1–14. doi:doi: 10.1029/2009GC002963
- Li ZX, Bogdanova SV, Collins AS, Davidson A, De Waele B, Ernst RE, Fitzsimons ICW, Fuck RA, Gladkochub DP, Jacobs J, Karlstrom KE, Lu S, Natapov LM, Pease V, Pisarevsky SA, Thrane K, Vernikovsky V (2008) Assembly, configuration, and break-up history of Rodinia: a synthesis. Precambrian Res 160:179–210CrossRefGoogle Scholar
- Ludwig KR (2001) User manual for Isoplot/Ex rev. 2.49. A geochronological toolkit for Microsoft Excel. Berkeley Geochronology Center, Special Publication 1: pp 56Google Scholar
- Mehnert KR (1968) Migmatites and the origin of granitic rocks. Elsevier Sci, New York, p 393Google Scholar
- Nehlig E, Genna A, Asfirane E (2002) A review of the Pan-African evolution of the Arabian Shield. GeoArabia 7:103–124Google Scholar
- Pearce JA, Harris BW, Tindle AG (1984) Trace element discrimination diagrams for the tectonic interpretation of granitic rocks. J Petrol 25:956–983Google Scholar
- Razin P, Leroy S, Robin C, Robinet J, Serra Kiel J, Bellahsen N, Grelaud C (2010) Dispositifs tecto-sédimentaires syn-rift et post-rift Oligo-Miocènes sur la marge sud du Golfe d’Aden. Paper presented at the RST, Bordeaux, Oct 2010Google Scholar
- Sun S–S, McDonough WF (1989) Chemical and isotopic systematics of ocean basalts: implications for mantle composition and process. In: Saunders AD, Norry MJ (eds) Magmatism in the Ocean Basins. Spec Pub Geol Soc Lond 42: 313–345Google Scholar
- Tucker RD, Ashwal LD, Torsvik TH (1999b) Neoproterozoic silicic magmatism in northern Madagascar, Seychelles and NW India: clues to Neoproterozoic supercontinent formation and dispersal. EOS Trans Am Geophys Union 80:372–373Google Scholar