Hostname: page-component-cd9895bd7-jn8rn Total loading time: 0 Render date: 2024-12-16T14:05:49.334Z Has data issue: false hasContentIssue false
  • English
  • Français

The origin of the ultramafic rocks of the Tulu Dimtu Belt, western Ethiopia – do they represent remnants of the Mozambique Ocean?

Published online by Cambridge University Press:  30 October 2017

MORGAN L. BLADES ,
JOHN FODEN ,
ALAN S. COLLINS ,
TADESSE ALEMU  and
GIRMA WOLDETINSAE
MORGAN L. BLADES*
Affiliation:
Centre for Tectonics, Resources and Exploration (TRaX), Department of Earth Sciences, University of Adelaide, Adelaide, SA 5005, Australia
JOHN FODEN
Affiliation:
Centre for Tectonics, Resources and Exploration (TRaX), Department of Earth Sciences, University of Adelaide, Adelaide, SA 5005, Australia
ALAN S. COLLINS
Affiliation:
Centre for Tectonics, Resources and Exploration (TRaX), Department of Earth Sciences, University of Adelaide, Adelaide, SA 5005, Australia
TADESSE ALEMU
Affiliation:
Mining Engineering Department, Unity University, P.O. Box 6722, Addis Ababa, Ethiopia
GIRMA WOLDETINSAE
Affiliation:
Research and Development Directorate, Ministry of Mines, Petroleum and Natural Gas, P.O. Box 486, Addis Ababa, Ethiopia
*
†Author for correspondence: [email protected]
Get access Rights & Permissions [Opens in a new window]

Abstract

The East African Orogen contains a series of high-strain zones that formed as Gondwana amalgamated. The Tulu Dimtu shear belt is one of these N–S structures within the Barka–Tulu Dimtu zone in western Ethiopia, and contains ultramafic bodies of equivocal origin. Identifying the petrogenetic origin of these enigmatic rocks provides evidence for the geodynamic significance of these shear zones. Owing to their altered state, these ultramafic rocks’ well-preserved chrome spinels provide the only reliable evidence for their source and tectonic affiliation. Chrome spinels have high Cr2O3 (30.04–68.76 wt %), while recalculated Fe2O3 (< 2 %) and TiO2 (0.01–0.51 %) values are low. The Cr# (molar Cr3+/Cr3+ + Al2+) and Mg# (Mg2+/Mg2+ + Fe2+) have averages of 0.88 and 0.22, respectively. Based on olivine–spinel equilibria, the calculated fO2 values (FMQ +3.03) for the dunites reveal a highly oxidized environment. This spinel chemistry (high Cr# > 0.6 and low Ti) supports a supra-subduction origin, with an oxidized mantle source more refractory than depleted MORB mantle (DMM). These spinel compositions indicate that some ultramafic bodies in western Ethiopia, including those from Daleti, Tulu and Dimtu, are serpentinized peridotites emplaced as obducted ophiolite complexes. By contrast, the ultramafic rocks from the Yubdo locality have a different spinel chemistry, with strong affiliation with igneous spinels formed in Alaskan-style mafic intrusions. These collective results suggest that regardless of their origin as supra-subduction ophiolites or as Alaskan-type intrusions, these spinels were formed on a convergent-subduction margin.

Keywords

Western Ethiopian Shieldchrome spinelAlaskan-type intrusionophiolite
Type
Original Articles
Information
Geological Magazine , Volume 156 , Issue 1 , January 2019 , pp. 62 - 82
Copyright
Copyright © Cambridge University Press 2017 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Abdel-Karim, A.-A. M., Ali, S., Helmy, H. M. & El-Shafei, S. A. 2016. A fore-arc setting of the Gerf ophiolite, Eastern Desert, Egypt: evidence from mineral chemistry and geochemistry of ultramafites. Lithos 263, 52–65.Google Scholar
Abdelsalam, M. & Stern, R. 1996. Sutures and shear zones in the Arabian-Nubian Shield. Journal of African Earth Sciences 23, 289–310.Google Scholar
Abraham, A. 1989. Tectonic History of the Pan-African Low-Grade Belt of Western Ethiopia. Addis Ababa: Ethiopian Institute of Geological Surveys.Google Scholar
Ahmed, A. H. 2013. Highly depleted harzburgite–dunite–chromitite complexes from the Neoproterozoic ophiolite, south Eastern Desert, Egypt: a possible recycled upper mantle lithosphere. Precambrian Research 233, 173–92.Google Scholar
Ahmed, A. & Arai, S. 2002. Unexpectedly high-PGE chromitite from the deeper mantle section of the northern Oman ophiolite and its tectonic implications. Contributions to Mineralogy and Petrology 143, 263–78.Google Scholar
Aldanmaz, E., Schmidt, M., Gourgaud, A. & Meisel, T. 2009. Mid-ocean ridge and supra-subduction geochemical signatures in spinel–peridotites from the Neotethyan ophiolites in SW Turkey: implications for upper mantle melting processes. Lithos 113, 691–708.Google Scholar
Alemu, T. 2004. Structural evolution of the Pan-African Tulu Dimtu Belt, western Ethiopia. In Proceedings of the 4th Ethiopian Geoscience and Mineral Engineering Association (EGMEA) (ed. Asrat, A.), pp. 188–94.Google Scholar
Alemu, T. & Abebe, T. 2000. Geology of the Gimbi Area. Addis Ababa: Geological Survey of Ethiopia.Google Scholar
Alemu, T. & Abebe, T. 2007. Geology and tectonic evolution of the Pan-African Tulu Dimtu Belt, Western Ethiopia. Online Journal of Earth Sciences 1, 24–42.Google Scholar
Allen, A. & Tadesse, G. 2003. Geological setting and tectonic subdivision of the Neoproterozoic orogenic belt of Tuludimtu, western Ethiopia. Journal of African Earth Sciences 36, 329–43.Google Scholar
Arai, S. 1992. Chemistry of chromian spinel in volcanic rocks as a potential guide to magma chemistry. Mineralogical Magazine 56, 173–84.Google Scholar
Arai, S. 1994. Characterization of spinel peridotites by olivine-spinel compositional relationships: review and interpretation. Chemical Geology 113, 191–204.Google Scholar
Arai, S. & Ishimaru, S. 2008. Insights into petrological characteristics of the lithosphere of mantle wedge beneath arcs through peridotite xenoliths: a review. Journal of Petrology 49, 665–95.Google Scholar
Arai, S., Kida, M., Abe, N. & Yurimoto, H. 2001. Petrology of peridotite xenoliths in alkali basalt (11 Ma) from Boun, Korea: an insight into the upper mantle beneath the East Asian continental margin. Journal of Mineralogical and Petrological Sciences 96, 89–99.Google Scholar
Arai, S. & Miura, M. 2016. Formation and modification of chromitites in the mantle. Lithos 264, 277–95.Google Scholar
Arai, S., Okamura, H., Kadoshima, K., Tanaka, C., Suzuki, K. & Ishimaru, S. 2011. Chemical characteristics of chromian spinel in plutonic rocks: implications for deep magma processes and discrimination of tectonic setting. Island Arc 20, 125–37.Google Scholar
Arai, S., Shimizu, Y., Ismail, S. & Ahmed, A. 2006. Low-T formation of high-Cr spinel with apparently primary chemical characteristics within podiform chromitite from Rayat, northeastern Iraq. Mineralogical Magazine 70, 499–508.Google Scholar
Arai, S., Takada, S., Michibayashi, K. & Kida, M. 2004. Petrology of peridotite xenoliths from Iraya volcano, Philippines, and its implication for dynamic mantle-wedge processes. Journal of Petrology 45, 369–89.Google Scholar
Arai, S. & Takahashi, N. 1987. A kaersutite-bearing dunite xenolith from Ichinomegata, northeastern Japan. The Journal of the Japanese Association of Mineralogists, Petrologists and Economic Geologists 82, 85–9.Google Scholar
Augé, T. 1987. Chromite deposits in the northern Oman ophiolite: mineralogical constraints. Mineralium Deposita 22, 1–10.Google Scholar
Ayalew, T., Bell, K., Moore, J. M. & Parrish, R. R. 1990. U–Pb and Rb–Sr geochronology of the western Ethiopian shield. Geological Society of America Bulletin 102, 1309–16.Google Scholar
Ayalew, T. & Peccerillo, A. 1998. Petrology and geochemistry of the Gore-Gambella plutonic rocks: implications for magma genesis and the tectonic setting of the Pan-African Orogenic Belt of western Ethiopia. Journal of African Earth Sciences 27, 397–416.Google Scholar
Azer, M. K. & Stern, R. J. 2007. Neoproterozoic (835–720 Ma) serpentinites in the Eastern Desert, Egypt: fragments of forearc mantle. The Journal of Geology 115, 457–72.Google Scholar
Bakor, A. R., Gass, I. G. & Neary, C. R. 1976. Jabal al Wask NW Saudi Arabia: an Eocambrian back arc ophiolite. Earth and Planetary Sciences 30, 1–9.Google Scholar
Ballhaus, C., Berry, R. & Green, D. 1991. High pressure experimental calibration of the olivine-orthopyroxene-spinel oxygen geobarometer: implications for the oxidation state of the upper mantle. Contributions to Mineralogy and Petrology 107, 27–40.Google Scholar
Ballhaus, C., Berry, R. & Green, D. 1994. High-pressure experimental calibration of the olivine-orthopyroxene-spinel oxygen geobarometer: implications for the oxidation state of the upper mantle. Contributions to Mineralogy and Petrology 118, 109–09.Google Scholar
Barnes, S. J. 2000. Chromite in komatiites, II. Modification during greenschist to mid-amphibolite facies metamorphism. Journal of Petrology 41, 387–409.Google Scholar
Barnes, S. J. & Roeder, P. L. 2001. The range of spinel compositions in terrestrial mafic and ultramafic rocks. Journal of Petrology 42, 2279–302.Google Scholar
Beccaluva, L. & Serri, G. 1988. Boninitic and low-Ti subduction-related lavas from intraoceanic arc-backarc systems and low-Ti ophiolites: a reappraisal of their petrogenesis and original tectonic setting. Tectonophysics 146, 291–315.Google Scholar
Belete, K., Mogessie, A., Hoinkes, G. & Ettinger, K. 2000. Platinum group minerals and chrome spinels in the Yubdo ultramafic rocks, western Ethiopia. Journal of African Earth Sciences 30 (4a) Special Abstract Issue, 18th Colloquium of African Geology, 10.Google Scholar
Berhe, S. M. 1990. Ophiolites in Northeast and East Africa: implications for Proterozoic crustal growth. Journal of the Geological Society, London 147, 41–57.Google Scholar
Blades, M. L., Collins, A. S., Foden, J., Payne, J. L., Xu, X., Alemu, T., Woldetinsae, G., Clark, C. & Taylor, R. J. 2015. Age and hafnium isotopic evolution of the Didesa and Kemashi Domains, western Ethiopia. Precambrian Research 270, 267–84.Google Scholar
Bodinier, J.-L. & Godard, M. 2003. Orogenic, ophiolitic, and abyssal peridotites. In Treatise on Geochemistry 2nd Ed., Vol. 3 (ed. Carlson, R. W.), pp. 103–70. Amsterdam: Elsevier.Google Scholar
Bonatti, E. & Michael, P. J. 1989. Mantle peridotites from continental rifts to ocean basins to subduction zones. Earth and Planetary Science Letters 91, 297–311.Google Scholar
Braathen, A., Grenne, T., Selassie, M. & Worku, T. 2001. Juxtaposition of Neoproterozoic units along the Baruda–Tulu Dimtu shear-belt in the East African Orogen of western Ethiopia. Precambrian Research 107, 215–34.Google Scholar
Chashchukhin, I., Votyakov, S., Pushkarev, E., Anikina, E., Mironov, A. & Uimin, S. 2002. Oxithermobarometry of ultramafic rocks from the Ural Platinum Belt. Geochemistry International 40, 762–78.Google Scholar
Chen, B., Suzuki, K., Tian, W., Jahn, B. & Ireland, T. 2009. Geochemistry and Os–Nd–Sr isotopes of the Gaositai Alaskan-type ultramafic complex from the northern North China craton: implications for mantle–crust interaction. Contributions to Mineralogy and Petrology 158, 683–702.Google Scholar
Collins, A. & Pisarevsky, S. 2005. Amalgamating eastern Gondwana: the evolution of the Circum-Indian Orogens. Earth-Science Reviews 71, 229–70.Google Scholar
deBari, S. M. & Coleman, R. G. 1989. Examination of the deep levels of an island arc: evidence from the Tonsina ultramafic-mafic assemblage, Tonsina, Alaska. Journal of Geophysical Research 94, 4373–91.Google Scholar
de Wit, M. & Aguma, A. 1977. Geology of the Ultramafic and Associated Rocks of Tulu Dimtu, Welega. Ethiopian Institute of Geological Surveys Report, 26.Google Scholar
Dick, H. J. B. 1989. Abyssal peridotites, very slow spreading ridges and ocean ridge magmatism. Magmatism in the Ocean Basins 42, 71–105.Google Scholar
Dick, H. J. & Bullen, T. 1984. Chromian spinel as a petrogenetic indicator in abyssal and alpine-type peridotites and spatially associated lavas. Contributions to Mineralogy and Petrology 86, 54–76.Google Scholar
Dick, H. J. & Natland, J. H. 1996. Late-stage melt evolution and transport in the shallow mantle beneath the East Pacific Rise. In Proceedings of the Ocean Drilling Program, Scientific Results, vol. 147 (eds Mével, C., Gillis, K. M., Allan, J. F. & Meyer, P. S.), pp. 103–34. College Station, Texas.Google Scholar
Dick, H. J. B. & Sinton, J. M. 1979. Compositional layering in alpine peridotites: evidence for pressure solution creep in the mantle. The Journal of Geology 87, 403–16.Google Scholar
Dilek, Y. & Flower, M. F. 2003. Arc-trench rollback and forearc accretion: 2. A model template for ophiolites in Albania, Cyprus, and Oman. In Ophiolites in Earth History (eds Dilek, Y. & Robinson, P. T.), pp. 43–68. Geological Society of London, Special Publication no. 218.Google Scholar
Dilek, Y. & Furnes, H. 2011. Ophiolite genesis and global tectonics: geochemical and tectonic fingerprinting of ancient oceanic lithosphere. Geological Society of America Bulletin 123, 387–411.Google Scholar
Dilek, Y. & Furnes, H. 2014. Ophiolites and their origins. Elements 10, 93–100.Google Scholar
El Bahariya, G. & Abd El-Wahed, M. 2003. Petrology, mineral chemistry and tectonic evolution of the northern part of Wadi Hafafit area, Eastern Desert, Egypt. In The Third International Conference on the Geology of Africa, Assiut University, Assiut (7–9 December 2003), Egypt, pp. 201–31.Google Scholar
El-Rahman, Y. A., Helmy, H. M., Shibata, T., Yoshikawa, M., Arai, S. & Tamura, A. 2012. Mineral chemistry of the Neoproterozoic Alaskan-type Akarem Intrusion with special emphasis on amphibole: implications for the pluton origin and evolution of subduction-related magma. Lithos 155, 410–25.Google Scholar
Escayola, M., Garuti, G., Zaccarini, F., Proenza, J. A., Bédard, J. H. & Van Staal, C. 2011. Chromitite and platinum-group-element mineralization at middle Arm Brook, central Advocate ophiolite complex, Baie Verte peninsula, Newfoundland, Canada. The Canadian Mineralogist 49, 1523–47.Google Scholar
Evans, K., Elburg, M. & Kamenetsky, V. 2012. Oxidation state of subarc mantle. Geology 40, 783–6.Google Scholar
Farahat, E. S. 2008. Chrome-spinels in serpentinites and talc carbonates of the El Ideid-El Sodmein District, central Eastern Desert, Egypt: their metamorphism and petrogenetic implications. Chemie der Erde-Geochemistry 68, 193–205.Google Scholar
Farahat, E., El Mahalawi, M., Hoinkes, G. & Abdel Aal, A. 2004. Continental back-arc basin origin of some ophiolites from the Eastern Desert of Egypt. Mineralogy and Petrology 82, 81–104.Google Scholar
Farahat, E. & Helmy, H. 2006. Abu Hamamid Neoproterozoic Alaskan-type complex, south Eastern Desert, Egypt. Journal of African Earth Sciences 45, 187–97.Google Scholar
Findlay, D. 1969. Origin of the Tulameen ultramafic-gabbro complex, southern British Columbia. Canadian Journal of Earth Sciences 6, 399–425.Google Scholar
Fritz, H., Abdelsalam, M., Ali, K. A., Bingen, B., Collins, A. S., Fowler, A. R., Ghebreab, W., Hauzenberger, C. A., Johnson, P. R., Kusky, T. M., Macey, P., Muhongo, S., Stern, R. J. & Viola, G. 2013. Orogen styles in the East African Orogen: a review of the Neoproterozoic to Cambrian tectonic evolution. Journal of African Earth Sciences 86, 65–106.Google Scholar
Frost, B. R. 1975. Contact metamorphism of serpentinite, chloritic blackwall and rodingite at Paddy-Go-Easy Pass, Central Cascades, Washington. Journal of Petrology 16, 272–313.Google Scholar
Frost, B. R. & Beard, J. S. 2007. On silica activity and serpentinization. Journal of Petrology 48, 1351–68.Google Scholar
Garuti, G., Pushkarev, E. V. & Zaccarini, F. 2002. Composition and paragenesis of Pt alloys from chromitites of the Uralian–Alaskan-type Kytlym and Uktus complexes, northern and central Urals, Russia. The Canadian Mineralogist 40, 357–76.Google Scholar
Garuti, G., Pushkarev, E. V., Zaccarini, F., Cabella, R. & Anikina, E. 2003. Chromite composition and platinum-group mineral assemblage in the Uktus Uralian-Alaskan-type complex (Central Urals, Russia). Mineralium Deposita 38, 312–26.Google Scholar
Grenne, T., Pedersen, R., Bjerkgård, T., Braathen, A., Selassie, M. & Worku, T. 2003. Neoproterozoic evolution of Western Ethiopia: igneous geochemistry, isotope systematics and U–Pb ages. Geological Magazine 140, 373–95.Google Scholar
Helmy, H. & El Mahallawi, M. 2003. Gabbro Akarem mafic-ultramafic complex, Eastern Desert, Egypt: a Late Precambrian analogue of Alaskan-type complexes. Mineralogy and Petrology 77, 85–108.Google Scholar
Helmy, H. M., El-Rahman, Y. M. A., Yoshikawa, M., Shibata, T., Arai, S., Tamura, A. & Kagami, H. 2014. Petrology and Sm–Nd dating of the Genina Gharbia Alaskan-type complex (Egypt): insights into deep levels of Neoproterozoic island arcs. Lithos 198, 263–80.Google Scholar
Helmy, H. M. & Mogessie, A. 2001. Gabbro Akarem, Eastern Desert, Egypt: Cu–Ni–PGE mineralization in a concentrically zoned mafic–ultramafic complex. Mineralium Deposita 36, 58–71.Google Scholar
Helmy, H. M., Yoshikawa, M., Shibata, T., Arai, S. & Kagami, H. 2015. Sm–Nd and Rb–Sr isotope geochemistry and petrology of Abu Hamamid intrusion, Eastern Desert, Egypt: an Alaskan-type complex in a backarc setting. Precambrian Research 258, 234–46.Google Scholar
Himmelberg, G. R. & Loney, R. A. 1995. Characteristics and Petrogenesis of Alaskan-Type Ultramafic-Mafic Intrusions, Southeastern Alaska. US Geological Survey Professional Paper 1564.Google Scholar
Himmelberg, G. R., Loney, R. A. & Craig, J. T. 1986. Petrogenesis of the Ultramafic Complex at the Blashke Islands, Southeastern Alaska. US Geological Survey Bulletin 1662.Google Scholar
Hussein, I., Kröner, A. & Reischmann, T. 2004. The Wadi Onib mafic-ultramafic complex: a Neoproterozoic supra-subduction zone ophiolite in the northern Red Sea hills of the Sudan. Developments in Precambrian Geology 13, 163–206.Google Scholar
Irvine, T. 1965. Chromian spinel as a petrogenetic indicator: Part 1. Theory. Canadian Journal of Earth Sciences 2, 648–72.Google Scholar
Irvine, T. 1967. Chromian spinel as a petrogenetic indicator: Part 2. Petrologic applications. Canadian Journal of Earth Sciences 4, 71–103.Google Scholar
Irvine, T. N. 1974. Petrology of the Duke Island ultramafic complex southeastern Alaska. Geological Society of America Memoirs 138, 1–244.Google Scholar
Ishii, K. 1992. Partitioning of non-coaxiality in deforming layered rock masses. Tectonophysics 210, 33–43.Google Scholar
Iyer, K., Austrheim, H., John, T. & Jamtveit, B. 2008. Serpentinization of the oceanic lithosphere and some geochemical consequences: constraints from the Leka Ophiolite Complex, Norway. Chemical Geology 249, 66–90.Google Scholar
Jaques, A. & Green, D. 1980. Anhydrous melting of peridotite at 0–15 kb pressure and the genesis of tholeiitic basalts. Contributions to Mineralogy and Petrology 73, 287–310.Google Scholar
Johnson, P., Andresen, A., Collins, A. S., Fowler, A., Fritz, H., Ghebreab, W., Kusky, T. & Stern, R. 2011. Late Cryogenian–Ediacaran history of the Arabian–Nubian Shield: a review of depositional, plutonic, structural, and tectonic events in the closing stages of the northern East African Orogen. Journal of African Earth Sciences 61, 167–232.Google Scholar
Johnson, T. E., Ayalew, T., Mogessie, A., Kruger, F. J. & Poujol, M. 2004. Constraints on the tectonometamorphic evolution of the Western Ethiopian Shield. Precambrian Research 133, 305–27.Google Scholar
Kamenetsky, V. S., Crawford, A. J. & Meffre, S. 2001. Factors controlling chemistry of magmatic spinel: an empirical study of associated olivine, Cr-spinel and melt inclusions from primitive rocks. Journal of Petrology 42, 655–71.Google Scholar
Kamenetsky, V. S., Sobolev, A. V., Eggins, S., Crawford, A. J. & Arculus, R. 2002. Olivine-enriched melt inclusions in chromites from low-Ca boninites, Cape Vogel, Papua New Guinea: evidence for ultramafic primary magma, refractory mantle source and enriched components. Chemical Geology 183, 287–303.Google Scholar
Kazmin, V. 1976. Ophiolites in the Ethiopian Basement. Ethiopian Institute of Geological Surveys, Note 35, 16 pp.Google Scholar
Kebede, T., Kloetzli, U. & Koeberl, C. 2001. U/Pb and Pb/Pb zircon ages from granitoid rocks of Wallagga area: constraints on magmatic and tectonic evolution of Precambrian rocks of western Ethiopia. Mineralogy and Petrology 71, 251–71.Google Scholar
Kebede, T., Koeberl, C. & Koller, F. 1999. Geology, geochemistry and petrogenesis of intrusive rocks of the Wallagga area, western Ethiopia. Journal of African Earth Sciences 29, 715–34.Google Scholar
Kebede, T., Koeberl, C. & Koller, F. 2001. Magmatic evolution of the Suqii-Wagga garnet-bearing two-mica granite, Wallagga area, western Ethiopia. Journal of African Earth Sciences 32, 193–221.Google Scholar
Kelemen, P. B., Whitehead, J., Aharonov, E. & Jordahl, K. A. 1995. Experiments on flow focusing in soluble porous media, with applications to melt extraction from the mantle. Journal of Geophysical Research: Solid Earth 100 (B1), 475–96.Google Scholar
Khalil, A. & Azer, M. 2007. Supra-subduction affinity in the Neoproterozoic serpentinites in the Eastern Desert, Egypt: evidence from mineral composition. Journal of African Earth Sciences 49, 136–52.Google Scholar
Khedr, M. Z. & Arai, S. 2013. Origin of Neoproterozoic ophiolitic peridotites in south Eastern Desert, Egypt, constrained from primary mantle mineral chemistry. Mineralogy and Petrology 107, 807–28.Google Scholar
Khedr, M. Z. & Arai, S. 2016. Petrology of a Neoproterozoic Alaskan-type complex from the Eastern Desert of Egypt: implications for mantle heterogeneity. Lithos 263, 15–32.Google Scholar
Khudeir, A. 1995. Chromian spinel-silicate chemistry in peridotite and orthopyroxenite relicts from ophiolitic serpentinites, Eastern Desert, Egypt. Bulletin of the Faculty of Science, Assiut University 24, 221–61.Google Scholar
Kimball, K. L. 1990. Effects of hydrothermal alteration on the compositions of chromian spinels. Contributions to Mineralogy and Petrology 105, 337–46.Google Scholar
Krause, J., Brügmann, G. E. & Pushkarev, E. V. 2007. Accessory and rock forming minerals monitoring the evolution of zoned mafic–ultramafic complexes in the Central Ural Mountains. Lithos 95, 19–42.Google Scholar
Leblanc, M. & Nicolas, A. 1992. Ophiolitic chromitites. International Geology Review 34, 653–86.Google Scholar
Le Mée, L., Girardeau, J. & Monnier, C. 2004. Mantle segmentation along the Oman ophiolite fossil mid-ocean ridge. Nature 432 (7014), 167–72.Google Scholar
Meert, J. G. 2003. A synopsis of events related to the assembly of eastern Gondwana. Tectonophysics 362, 1–40.Google Scholar
Meert, J. G. & Lieberman, B. S. 2008. The Neoproterozoic assembly of Gondwana and its relationship to the Ediacaran–Cambrian radiation. Gondwana Research 14, 5–21.Google Scholar
Mellini, M., Rumori, C. & Viti, C. 2005. Hydrothermally reset magmatic spinels in retrograde serpentinites: formation of “ferritchromit” rims and chlorite aureoles. Contributions to Mineralogy and Petrology 149, 266–75.Google Scholar
Merdith, A. S., Collins, A. S., Williams, S. E., Pisarevsky, S., Foden, J. F., Archibald, D. A., Blades, M. L., Alessio, B. L., Armistead, S., Plavsa, D., Clark, C. & , D.R.M. 2017. A full plate global reconstruction of the Neoproterozoic. Gondwana Research 50, 84–134.Google Scholar
Metcalf, R. V. & Shervais, J. W. 2008. Suprasubduction-zone ophiolites: is there really an ophiolite conundrum? In Ophiolites, Arcs, and Batholiths: A Tribute to Cliff Hopson (eds Wright, J. E. & Shervais, J. W.), pp. 191–222. Geological Society of America Special Papers no. 438.Google Scholar
Mogessie, A., Belete, K. & Hoinkes, G. 2000. Yubdo-Tulu Dimtu mafic-ultramafic belt, Alaskan-type intrusions in western Ethiopia: its implication to the Arabian-Nubian Shield and tectonics of the Mozambique Belt. Journal of African Earth Sciences 30, 62.Google Scholar
Molly, E. 1959. Platinum deposits of Ethiopia. Economic Geology 54, 467–77.Google Scholar
Niu, Y. & Hekinian, R. 1997. Spreading-rate dependence of the extent of mantle melting beneath ocean ridges. Nature 385 (6614), 326.Google Scholar
Pallister, J. S., Stacey, J. S., Fischer, L. B. & Premo, W. R. 1988. Precambrian ophiolites of Arabia: geologic settings, U–Pb geochronology, Pb-isotope characteristics, and implications for continental accretion. Precambrian Research 38, 1–54.Google Scholar
Parkinson, I. J. & Arculus, R. J. 1999. The redox state of subduction zones: insights from arc-peridotites. Chemical Geology 160, 409–23.Google Scholar
Parkinson, I. J. & Pearce, J. A. 1998. Peridotites from the Izu–Bonin–Mariana forearc (ODP Leg 125): evidence for mantle melting and melt–mantle interaction in a supra-subduction zone setting. Journal of Petrology 39, 1577–618.Google Scholar
Pearce, J. A., Barker, P., Edwards, S., Parkinson, I. & Leat, P. 2000. Geochemistry and tectonic significance of peridotites from the South Sandwich arc–basin system, South Atlantic. Contributions to Mineralogy and Petrology 139, 36–53.Google Scholar
Pearce, J. A., Lippard, S. & Roberts, S. 1984. Characteristics and tectonic significance of supra-subduction zone ophiolites. In Marginal Basin Geology: Volcanic and Associated Sedimentary and Tectonic Processes in Modern and Ancient Marginal Basins (eds Kokelaar, B. P & Howells, M. F.), pp. 77–94. Geological Society of London, Special Publication no. 16.Google Scholar
Pinsent, R. & Hirst, D. 1977. The metamorphism of the Blue River ultramafic body, Cassiar, British Columbia, Canada. Journal of Petrology 18, 567–94.Google Scholar
Proenza, J., Gervilla, F., Melgarejo, J. & Bodinier, J.-L. 1999. Al-and Cr-rich chromitites from the Mayari-Baracoa ophiolitic belt (eastern Cuba); consequence of interaction between volatile-rich melts and peridotites in suprasubduction mantle. Economic Geology 94, 547–66.Google Scholar
Proenza, J. A., Zaccarini, F., Lewis, J. F., Longo, F. & Garuti, G. 2007. Chromian spinel composition and the platinum-group minerals of the PGE-rich Loma Peguera chromitites, Loma Caribe peridotite, Dominican Republic. The Canadian Mineralogist 45, 631–48.Google Scholar
Rahman, E. A., Harms, U., Schandelmeier, H., Franz, G., Darbyshire, D., Horn, P. & Muller–Sohnius, D. 1990. A new ophiolite occurrence in NW Sudan; constraints on late Proterozoic tectonism. Terra Nova 2, 363–76.Google Scholar
Roeder, P. L. & Campbell, I. H. 1985. The effect of postcumulus reactions on composition of chrome-spinels from the Jimberlana intrusion. Journal of Petrology 26, 763–86.Google Scholar
Rollinson, H. 2008. The geochemistry of mantle chromitites from the northern part of the Oman ophiolite: inferred parental melt compositions. Contributions to Mineralogy and Petrology 156, 273–88.Google Scholar
Rollinson, H. & Adetunji, J. 2015 a. Chromite in the mantle section of the Oman Ophiolite: implications for the tectonic evolution of the Oman ophiolite. Acta Geologica Sinica (English Edition) 89 (s2), 73–6.Google Scholar
Rollinson, H. & Adetunji, J. 2015 b. The geochemistry and oxidation state of podiform chromitites from the mantle section of the Oman ophiolite: a review. Gondwana Research 27, 543–54.Google Scholar
Scowen, P. A. H., Roeder, P. L. & Helz, R. T. 1991. Reequilibration of chromite within Kilauea Iki lava lake, Hawaii. Contributions to Mineralogy and Petrology 107, 8–20.Google Scholar
Shervais, J. W. 2001. Birth, death, and resurrection: the life cycle of suprasubduction zone ophiolites. Geochemistry, Geophysics, Geosystems 2, 1010. doi: 10.1029/2000GC000080.Google Scholar
Snoke, A. W., Quick, J. E. & Bowman, H. R. 1981. Bear Mountain Igneous Complex, Klamath Mountains, California: an ultrabasic to silicic calc-alkaline suite. Journal of Petrology 22, 501–52.Google Scholar
Sobolev, A. t. & Batanova, V. 1995. Mantle lherzolites of the Troodos ophiolite complex, Cyprus-clinopyroxene geochemistry. Petrology 3, 440–8.Google Scholar
Springer, R. K. 1974. Contact metamorphosed ultramafic rocks in the western Sierra Nevada foothills, California. Journal of Petrology 15, 160–95.Google Scholar
Stern, R. J. 1994. Arc-assembly and continental collision in the Neoproterozoic African Orogen: implications for the consolidation of Gondwanaland. Annual Review of Earth and Planetary Sciences 22, 319–51.Google Scholar
Stern, R. 2005. Evidence from ophiolites, blueschists, and ultrahigh-pressure metamorphic terranes that the modern episode of subduction tectonics began in Neoproterozoic time. Geology 33, 557–60.Google Scholar
Stern, R. J., Johnson, P. R., Kröner, A. & Yibas, B. 2004. Neoproterozoic ophiolites of the Arabian-Nubian shield. Developments in Precambrian Geology 13, 95–128.Google Scholar
Tadesse, G. & Allen, A. 2004. Geochemistry of metavolcanics from the Neoproterozoic Tuludimtu orogenic belt, Western Ethiopia. Journal of African Earth Sciences 39, 177–85.Google Scholar
Tadesse, G. & Allen, A. 2005. Geology and geochemistry of the Neoproterozoic Tuludimtu Ophiolite suite, western Ethiopia. Journal of African Earth Sciences 41, 192–211.Google Scholar
Takahashi, E. & Ito, E. 1987. Mineralogy of mantle peridotite along a model geotherm up to 700 km depth. In High-Pressure Research in Mineral Physics: A Volume in Honor of Syun-iti Akimoto (eds Manghnani, M. H. & Syono, Y.), pp. 427–43. American Geophysical Union, Washington, DC, USA.Google Scholar
Tamura, A. & Arai, S. 2006. Harzburgite–dunite–orthopyroxenite suite as a record of supra-subduction zone setting for the Oman ophiolite mantle. Lithos 90, 43–56.Google Scholar
Taylor, H. P. Jr & Noble, J. A. 1969. Origin of magnetite in the zoned ultramafic complexes of southeastern Alaska. Magmatic Ore Deposits 4, 209–30.Google Scholar
Tefera, M. 1991. Geology of the Kurmuk and Asosa Area. Ethiopian Institutes of Geological Surveys Draft Report 109.Google Scholar
Uysal, I., Tarkian, M., Sadiklar, M. B., Zaccarini, F., Meisel, T., Garuti, G. & Heidrich, S. 2009. Petrology of Al-and Cr-rich ophiolitic chromitites from the Muğla, SW Turkey: implications from composition of chromite, solid inclusions of platinum-group mineral, silicate, and base-metal mineral, and Os-isotope geochemistry. Contributions to Mineralogy and Petrology 158, 659–74.Google Scholar
Whattam, S. A. & Stern, R. J. 2011. The ‘subduction initiation rule’: a key for linking ophiolites, intra-oceanic forearcs, and subduction initiation. Contributions to Mineralogy and Petrology 162, 1031–45.Google Scholar
Woldemichael, B. W. & Kimura, J.-I. 2008. Petrogenesis of the Neoproterozoic Bikilal-Ghimbi gabbro, Western Ethiopia. Journal of Mineralogical and Petrological Sciences 103, 23–46.Google Scholar
Woldemichael, B. W., Kimura, J.-I., Dunkley, D. J., Tani, K. & Ohira, H. 2010. SHRIMP U–Pb zircon geochronology and Sr–Nd isotopic systematic of the Neoproterozoic Ghimbi-Nedjo mafic to intermediate intrusions of Western Ethiopia: a record of passive margin magmatism at 855 Ma? International Journal of Earth Sciences 99, 1773–90.Google Scholar
Woldie, K. & Nigussie, T. 1996. Geological Map of Ethiopia. Addis Ababa: Geological Survey of Ethiopia.Google Scholar
Yamamoto, K., Masutani, Y., Nakamura, N. & Ishii, T. 1992. REE characteristics of mafic rocks from a fore-arc seamount in the Izu-Ogasawara region, western Pacific. Geochemical Journal 26, 411–23.Google Scholar
Zhou, M.-F. & Bai, W.-J. 1992. Chromite deposits in China and their origin. Mineralium Deposita 27, 192–9.Google Scholar
Zhou, M.-F. & Robinson, P. T. 1997. Origin and tectonic environment of podiform chromite deposits. Economic Geology 92, 259–62.Google Scholar
Zhou, M.-F., Robinson, P. & Bai, W. 1994. Formation of podiform chromitites by melt/rock interaction in the upper mantle. Mineralium Deposita 29, 98–101.Google Scholar
Supplementary material: File

Blades et al supplementary material

Blades et al supplementary material 1

Download Blades et al supplementary material(File)
File 210.2 KB