Geochemistry of the Panjal Traps basalts (NW Himalaya): records of the Pangea Permian break-up

AbstractThe late Lower to Middle Permian Panjal Traps (NW Himalaya, India-Pakistan) represent the greatest magmatic province erupted on the northern Indian platform during the Neotethys opening. New geochemical and isotopic analyses were performed on basalts from the eastern borders of the traps (SE Zanskar-NW Spiti area) in order to characterize this volcanism, to discuss its compositional variations in comparison to Panjal counterparts and its relationships with the opening of Neotethys. Lavas show features of tholeiitic low-Ti (< 1.6%) continental flood basalts with LREE, Th enrichments and Nb-Ta negative anomalies. Trace element ratios combined with εNdi values (−3.6 to +0.9) and high Pb isotopic ratios suggest that these tholeiitic basalts were derived from an OIB-like mantle contaminated at various degrees by a continental crust component. Previous geochemical features are broadly similar to those of the coeval Panjal volcanic sequences identified westwards (Ladakh, Kashmir and Pakistan). Present geochemical constraints obtained for the Panjal Traps basalts suggest they originated from rapid effusion of tholeiitic melts during opening of the Neotethys Ocean. Similar magmatism implying an OIB-type reservoir is contemporaneously recognized on and along the adjacent Arabian platform. Both Indian and Arabian Permian volcanics were emplaced during coeval syn-rift to post rift transition. These Lower to Middle Permian south Neotethyan continental flood magmatism are regarded as associated to a passive rifting. In this scheme, OIB-type isotopic signature would be related either to a melting episode of syn-rift up-welling mantle plumes or to a melting of a regional abnormally hot and enriched mantle.

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Enriched mantle components in Proterozoic continental-flood basalts of the Cape Smith foldbelt, northern Québec

Lithos ◽

10.1016/s0024-4937(03)00063-x ◽

2003 ◽

Vol 71 (1) ◽

pp. 1-17 ◽

Cited By ~ 14

Author(s):

S. Modeland ◽

D. Francis ◽

A. Hynes

Keyword(s):

Flood Basalts ◽

Continental Flood Basalts ◽

Enriched Mantle

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Geochemical Constraints on the Mantle Source of the Upper Permian Emeishan Continental Flood Basalts, Southwestern China

International Geology Review ◽

10.1080/00206810109465009 ◽

2001 ◽

Vol 43 (3) ◽

pp. 213-225 ◽

Cited By ~ 122

Author(s):

Xie-Yan Song ◽

Mei-Fu Zhou ◽

Zheng-Qian Hou ◽

Zhi-Min Cao ◽

Yun-Liang Wang ◽

...

Keyword(s):

Mantle Source ◽

Upper Permian ◽

Southwestern China ◽

Flood Basalts ◽

Continental Flood Basalts ◽

Geochemical Constraints

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The Mugford Group Volcanics of Labrador: Age, Geochemistry, and Tectonic Setting

Canadian Journal of Earth Sciences ◽

10.1139/e75-109 ◽

1975 ◽

Vol 12 (7) ◽

pp. 1196-1208 ◽

Cited By ~ 10

Author(s):

Jackson M. Barton Jr.

Keyword(s):

Tectonic Setting ◽

Regional Metamorphism ◽

Volcanic Rocks ◽

Phosphorus Fractionation ◽

Flood Basalts ◽

Continental Flood Basalts ◽

The North ◽

Isotopic Analyses ◽

Igneous Activity ◽

North Atlantic Craton

The Mugford Group is a sequence of volcanic and sedimentary rocks exposed within the Khaumayät (Kaumajet) Mountains of Labrador. Separated from an intensely deformed and deeply eroded Archean basement complex by an angular unconformity, these rocks are nearly everywhere flat-lying and only locally altered. The volcanic rocks within the Mugford Group are of three types: tholeiitic basalts, komatiitic basalts and greenstones. A phosphorus fractionation diagram indicates that the tholeiitic and komatiitic basalts may be differentiates of a common magma. The greenstones, however, have undergone a separate crystallization history, but plot within the field of tholeiitic basalts on a FMA diagram, suggesting they were originally tholeiites. K–Ar whole-rock ages show that the Mugford volcanics are at least 1490 m.y. old. Rb–Sr whole-rock isotopic analyses of the tholeiitic and komatiitic basalts and the greenstones define an isochron of 2369 ± 55 m.y. with an initial 87Sr/86Sr ratio of 0.7033 ± 0.0002. This age is interpreted as approximating the time of extrusion of the Mugford volcanics. The low initial 87Sr/86Sr ratio indicates that the magmas giving rise to these rocks were not appreciably contaminated with older crustal material.The Mugford volcanics are presently the oldest recognized continental flood basalts. Their extrusion apparently occurred contemporaneously with the intrusion of the Okhakh granite at Okhakh (Okak) Harbour, 25 km to the south. This suggests that while no regional metamorphism accompanied extrusion of these volcanics, some local igneous activity did occur at that time. The Mugford volcanics may represent the extrusive equivalents of numerous basic dikes that were intruded during the final stages of stabilization of the North Atlantic craton.

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The Michael Gabbro and other Mesoproterozoic lithospheric probes in southern and central Labrador

Canadian Journal of Earth Sciences ◽

10.1139/e17-127 ◽

1997 ◽

Vol 34 (12) ◽

pp. 1566-1580 ◽

Cited By ~ 8

Author(s):

Ronald F. Emslie ◽

Michael A. Hamilton ◽

Charles F. Gower

Keyword(s):

Crustal Contamination ◽

Isotopic Signature ◽

Geochemical Data ◽

Magmatic Activity ◽

Flood Basalts ◽

Grenville Province ◽

Continental Flood Basalts ◽

The North ◽

Basement Rocks ◽

Northwestern Margin

The Michael Gabbro (1426 Ma) and the Shabogamo Gabbro (1459 Ma) represent two large diabase intrusive episodes that affected the northwestern margin of the northeastern Grenville Province. Both have sustained variable effects of subsequent Grenvillian metamorphism. Other broadly contemporaneous magmatic activity in the region includes the formation of Elsonian anorthosite–granitoid complexes (1.46–1.29 Ga) that intruded Churchill Province and Nain Province rocks to the north, the Harp dykes (1.27 Ga), and Mealy dykes (~1.25 Ga). Petrologic and geochemical data show that the Michael Gabbro and Shabogamo Gabbro are similar, with the latter displaying more cumulate rock characteristics, and the former having compositions closer to those of rapidly cooled magma. Both have compositions comparable to those of other continental diabases and to some continental flood basalts. Sr and Nd initial isotopic compositions of Michael Gabbro (εNd(1426 Ma) = −4.7 to −6.0, ISr(1426 Ma) = 0.7032–0.7044) and Shabogamo Gabbro (εNd(1459 Ma) = −4.0 to −5.5, ISr(1459 Ma) = 0.7020–0.7060) are alike and overlap, suggesting similar sources and processes of development. Comparisons with other nearly contemporary mafic suites in central and southern Labrador show that only the Mealy dykes have a distinctly more radiogenic isotopic signature. Paradoxically, other mafic suites that intrude older basement rocks north of the Grenville Front have less enriched Nd signatures than do those that intrude younger basement rocks south of the front. The argument is made that the subcontinental lithospheric mantle, and not crustal contamination, played the most influential role in evolution of the magmas.

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Geochemical Variation of Miocene Basalts within Shikoku Basin: Magma Source Compositions and Geodynamic Implications

Minerals ◽

10.3390/min11010025 ◽

2020 ◽

Vol 11 (1) ◽

pp. 25

Author(s):

Shuang-Shuang Chen ◽

Tong Hou ◽

Jia-Qi Liu ◽

Zhao-Chong Zhang

Keyword(s):

Japan Sea ◽

Isotopic Signature ◽

Magma Source ◽

Isotopic Compositions ◽

Enriched Mantle ◽

Shikoku Basin ◽

Depleted Mantle ◽

Parece Vela Basin ◽

Back Arc ◽

Ocean Ridge

Shikoku Basin is unique as being located within a trench-ridge-trench triple junction. Here, we report mineral compositions, major, trace-element, and Sr-Nd-Pb isotopic compositions of bulk-rocks from Sites C0012 (>18.9 Ma) and 1173 (13–15 Ma) of the Shikoku Basin. Samples from Sites C0012 and 1173 are tholeiitic in composition and display relative depletion in light rare earth elements (REEs) and enrichment in heavy REEs, generally similar to normal mid-ocean ridge basalts (N-MORB). Specifically, Site C0012 samples display more pronounced positive anomalies in Rb, Ba, K, Pb and Sr, and negative anomalies in Th, U, Nb, and Ta, as well as negative Nb relative to La and Th. Site 1173 basalts have relatively uniform Sr-Nd-Pb isotopic compositions, close to the end member of depleted mantle, while Site C0012 samples show slightly enriched Sr-Nd-Pb isotopic signature, indicating a possible involvement of enriched mantle 1 (EM1) and EM2 sources, which could be attributed to the metasomatism of the fluids released from the dehydrated subduction slab, but with the little involvement of subducted slab-derived sedimentary component. Additionally, the Shikoku Basin record the formation of the back-arc basin was a mantle conversion process from an island arc to a typical MORB. The formation of the Shikoku Basin is different from that of the adjacent Japan Sea and Parece Vela Basin, mainly in terms of the metasomatized subduction-related components, the nature of mantle source, and partial melting processes.

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