Geology and geochemistry of the Neoproterozoic Tuludimtu Ophiolite suite, western Ethiopia

Tadesse, Gebremedhin; Allen, Alistair

doi:10.1016/j.jafrearsci.2005.04.001

Cited by 29 publications

(32 citation statements)

References 38 publications

(96 reference statements)

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“…The granitoids compositionally ranges from undiformed to foliated diorite to granites [8]- [13] [23].…”

Section: Geological and Tectonic Settingmentioning

confidence: 99%

Geology, Geochemistry and Geochronology of the Kenticha Rare Metal Granite Pegmatite, Adola Belt, Southern Ethiopia: A Review

Mohammedyasin¹

2017

IJG

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This work reviews the geology, geochemistry and geochronology and discusses the spatial and temporal relationship of the granite pegmatite and the rare metal mineralization of the Kenticha granite pegmatite, southern Ethiopia using published and unpublished works to give a comprehensive understanding about the formation of the mineral deposit. The Kenticha rare metal pegmatite belt comprises several groups of pegmatites which show a high magmatic fractionation, regional and compositional zoning, mineralogical assemblage, and secondary alterations. The internal zonation shows high degree of evolution from the border to the core zone during crystallization and solidification of the leucogranitic to pegmatitic melt. Tantalum mineralization at Kenticha includes zoned tantalite-(Mn) and columbite-(Mn), as well as microlite, pyrochlore, uranmicrolite, and rare tapiolite, ixiolite/wodginite and Ta-bearing rutile. The tectonic setting of the Kenticha granite pegmatite in the Within Plate Granite (WPG) to syn-Collisional Granite (syn-COLG) suites and probably sourced from extreme fractionation of syn-to late tectonic granites or anatexis process of the metasedimentary rocks in the area. The emplacement of the Kenticha pegmatite was at ca. 530 Ma and temporally related to the post-collisional phase of granitic magmatism at 570 -520 Ma, after the last tectonic stage of east African orogeny during the late stage of Gondwana assembly.

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“…The granitoids compositionally ranges from undiformed to foliated diorite to granites [8]- [13] [23].…”

Section: Geological and Tectonic Settingmentioning

confidence: 99%

Geology, Geochemistry and Geochronology of the Kenticha Rare Metal Granite Pegmatite, Adola Belt, Southern Ethiopia: A Review

Mohammedyasin¹

2017

IJG

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“…1b) overall has been interpreted in terms of early rifting and associated sedimentation, followed by subduction and island-arc formation, arc-accretion and finally protracted continent-continent (East and West Gondwana) collision (e.g., Kazmin et al 1978;Stern 1994). Linear belts of highly deformed mafic-ultramafic bodies within low-grade (ANS-like) terranes have been interpreted as suture zones containing dismembered ophiolitic rocks (e.g., Kazmin et al 1978;Berhe 1990;Ayalew et al 1990;Abdelsalam and Stern 1996;Allen and Tadesse 2003;Tadesse and Allen 2005). Tadesse and Allen (2005) named this dismembered ophiolites as the Tuludimtu Ophiolite.…”

Section: Regional Geology and Tectonic Settingmentioning

confidence: 99%

“…Linear belts of highly deformed mafic-ultramafic bodies within low-grade (ANS-like) terranes have been interpreted as suture zones containing dismembered ophiolitic rocks (e.g., Kazmin et al 1978;Berhe 1990;Ayalew et al 1990;Abdelsalam and Stern 1996;Allen and Tadesse 2003;Tadesse and Allen 2005). Tadesse and Allen (2005) named this dismembered ophiolites as the Tuludimtu Ophiolite. However, unequivocal evidences for dismembered ophiolites are often lacking in the WES.…”

Section: Regional Geology and Tectonic Settingmentioning

confidence: 99%

“…The eastern CVST is a relatively narrow N-S trending strip of ultramafic and mafic volcanic rocks and related plutons. These are associated with marine sediments and thus are considered to be dismembered ophiolite (Tadesse and Allen 2005). The eastern CVST has been interpreted as a suture zone by several authors (e.g., Kazmin et al 1978;Berhe 1990;Tadesse and Allen 2005).…”

Section: Regional Geology and Tectonic Settingmentioning

confidence: 99%

“…These are associated with marine sediments and thus are considered to be dismembered ophiolite (Tadesse and Allen 2005). The eastern CVST has been interpreted as a suture zone by several authors (e.g., Kazmin et al 1978;Berhe 1990;Tadesse and Allen 2005). EMGT consists of migmatitic biotite to biotite-hornblende granitoid orthogneiss, whereas WMGT is dominated by biotite to biotite-hornblende gneiss (Alemu and Abebe 2000).…”

Section: Regional Geology and Tectonic Settingmentioning

confidence: 99%

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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?

Woldemichael

Kimura

Dunkley

et al. 2009

Int J Earth Sci (Geol Rundsch)

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The reworked Pre-Neoproterozoic and juvenile Neoproterozoic terrane of the Western Ethiopian Shield (WES) consists of three N-S trending terranes. These are the western migmatitic gneissic terrane, the central metavolcano sedimentary terrane (CVST) and the eastern migmatitic gneissic terrane. The eastern part of the CVST mostly consists of suture-related ultramafic-metasedimentary complexes, whereas metavolcanics predominate in the western part. Gabbroic to granitic intrusions frequently occur in the CVST and in adjacent areas. New zircon SHRIMP U-Pb ages for two gabbros and three diorites in the Ghimbi-Nedjo region of the WES indicate magmatic crystallization ages. Two pulses of magmatism, at 860-850 and 795-785 Ma, are documented with the former for the first time. The tholeiitic Kemashi diorite and BikilalGhimbi gabbros have oceanic affinities and yield U/Pb zircon ages of 856.3 ± 9.8 and 846.0 ± 7.6 Ma, respectively. The calc-alkaline Gebeya Kemisa pyroxene diorite, and the Senbet Dura hornblende diorite plus the tholeiitic Wayu Meni gabbro, which collectively have arc-back arc characteristics are indistinguishable at ages of 794.3 ± 9.4, 787.7 ± 8.8 and 778.1 ± 6.3 Ma, respectively. Positive eNd (4.5-7.0) and low initial 87 Sr/ 86 Sr (0.7029 ± 0.0002) and a mean T DM model age of 0.95 Ga for the GhimbiNedjo region (mean T DM model age of 0.95 Ga for the WES overall) indicate that the magmas were generated from juvenile Neoproterozoic depleted mantle sources, with no discernable involvement of pre-Neoproterozoic continental crust. The occurrence of gabbros and diorites with oceanic tholeiite affinities combined with the new ages suggests that the intrusions were emplaced in the earliest stages of the rifting of Rodinia. This event in the WES led to the development of a passive margin and associated plume-type magmatism at *855 Ma. The two intrusive groups with differing magma chemistry and ages suggest that the earliest magmatism was tholeiitic and associated with the passive margin system followed by continental breakup to form the Mozambique Ocean. The combination of tholeiitic and calc-alkaline magmatism was related to arc and back-arc basin formation and later terrane accretion (*830-690 Ma).

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Compositional and Sr‐Nd isotopic features of the Xiejiayao ophiolite in the North Qilian Orogenic Belt, NW China: Implications for the petrogenesis and tectonic setting

Zhao

et al. 2022

Geological Journal

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The ophiolites along the North Qilian Orogenic Belt are considered to be fragments of ancient oceanic crusts and lithospheric mantle of the Palaeozoic North Qilian Ocean (a branch of the Proto‐Tethys). Compared with other ophiolites in this belt, the genesis of the Xiejiayao ophiolite has been poorly studied so far, making it difficult to understand the tectonic evolution of the ocean. In this study, we present new compositional and Sr‐Nd isotopic analyses of basaltic rocks from the Xiejiayao ophiolite to shed light on its petrogenesis and geodynamic background. These oceanic basalts are characterized by flat REE patterns, low elemental ratios of high‐field‐strength elements (e.g., La/Sm, Sm/Yb, La/Yb, Gd/Yb, [Th/Yb]PM) and abundant spinels, implying that they were generated via partial melting in the spinel stability field of the mantle. Their positive εNd(t) values (6.1–8.4), high Zr/Nb (43.65–79.40) as well as low Nb/Ta (10.91–15.09), Zr/Hf (34.64–39.28), and Nb/Yb (0.41–0.59) ratios further reflect that the ancient mantle had already become depleted to some extent before the onset of the Palaeozoic ocean. Additionally, basalts share many geochemical similarities (e.g., Zr, Y, Ti, and V) with both mid‐ocean ridge and island arc basalts. This supports the strong likelihood of origin in a back‐arc basin close to the suprasubduction zone for the ophiolite. Therefore, accompanied by the northward subduction of the oceanic lithosphere during the early Palaeozoic, a large‐scale back‐arc basin developed progressively in response to the back‐arc expansion. The Xiejiayao basaltic magmas were generated in the back‐arc basin via partial melting of the depleted mantle and their source was probably mixed with subducted melts/fluids from the dehydration and melting of oceanic slabs and sediments.

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Geology and geochemistry of the Neoproterozoic Tuludimtu Ophiolite suite, western Ethiopia

Cited by 29 publications

References 38 publications

Geology, Geochemistry and Geochronology of the Kenticha Rare Metal Granite Pegmatite, Adola Belt, Southern Ethiopia: A Review

Geology, Geochemistry and Geochronology of the Kenticha Rare Metal Granite Pegmatite, Adola Belt, Southern Ethiopia: A Review

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?

Compositional and Sr‐Nd isotopic features of the Xiejiayao ophiolite in the North Qilian Orogenic Belt, NW China: Implications for the petrogenesis and tectonic setting

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