Microcontinent subduction and S-type volcanism prior to India–Asia collision

AbstractContinental crust has long been considered too buoyant to be subducted beneath another continent, although geophysical evidence in collision zones predict continental crust subduction. This is particularly significant where upper continental crust is detached allowing the lower continental crust to subduct, albeit the mechanism of such subduction and recycling of the upper continental crust remain poorly understood. Here, we investigate Paleocene S-type magmatic and volcanic rocks from the Linzizong volcanic succession in the southern Lhasa block of Tibet. These rocks exhibit highly enriched 87Sr/86Sr, 207Pb/206Pb and 208Pb/206Pb together with depleted 143Nd/144Nd isotope ratios. The geochemical and isotopic features of these rocks are consistent with those of modern upper continental crust. We conclude that these Paleocene S-type volcanic and magmatic rocks originated from the melting of the upper continental crust from microcontinent subduction during the late stage of India–Asia convergence.

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New approaches to crustal evolution studies and the origin of granitic rocks: what can the Lu-Hf and Re-Os isotope systems tell us?

Earth and Environmental Science Transactions of the Royal Society of Edinburgh ◽

10.1017/s0263593300006738 ◽

1996 ◽

Vol 87 (1-2) ◽

pp. 339-352 ◽

Cited By ~ 19

Author(s):

Clark M. Johnson ◽

Steven B. Shirey ◽

Karin M. Barovich

Keyword(s):

Continental Crust ◽

Isotope Ratios ◽

Granitic Rocks ◽

Nd Isotope ◽

Volcanic Arcs ◽

Depleted Mantle ◽

Os Isotopes ◽

Isotope System ◽

Os Isotope

ABSTRACT:The Lu-Hf and Re-Os isotope systems have been applied sparsely to elucidate the origin of granites, intracrustal processes and the evolution of the continental crust. The presence or absence of garnet as a residual phase during partial melting will strongly influence Lu/Hf partitioning, making the Lu–Hf isotope system exceptionally sensitive to evaluating the role of garnet during intracrustal differentiation processes. Mid-Proterozoic (1·1–1·5Ga ) ‘anorogenic’ granites from the western U.S.A. appear to have anomalously high εHf values, relative to their εNd values, compared with Precambrian orogenic granites from several continents. The Hf-Nd isotope variations for Precambrian orogenic granites are well explained by melting processes that are ultimately tied to garnet-bearing sources in the mantle or crust. Residual, garnet-bearing lower and middle crust will evolve to anomalously high εHf values over time and may be the most likely source for later ‘anorogenic’ magmas. When crustal and mantle rocks are viewed together in terms of Hf and Nd isotope compositions, a remarkable mass balance is apparent for at least the outer silicate earth where Precambrian orogenic continental crust is the balance to the high-εHf depleted mantle, and enriched lithospheric mantle is the balance to the low-εHf depleted mantle.Although the continental crust has been envisioned to have exceptionally high Re/Os ratios and very radiogenic Os isotope compositions, new data obtained on magnetite mineral separates suggest that some parts of the Precambrian continental crust are relatively Os-rich and non-radiogenic. It remains unclear how continental crust may obtain non-radiogenic Os isotope ratios, and these results have important implications for Re-Os isotope evolution models. In contrast, Phanerozoic batholiths and volcanic arcs that are built on young mafic lower crust may have exceptionally radiogenic Os isotope ratios. These results highlight the unique ability of Os isotopes to identify young mafic crustal components in orogenic magmas that are essentially undetectable using other isotope systems such as O, Sr, Nd and Pb.

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Zircon U-Pb ages, geochemistry, and Sr-Nd isotope ratios for early cretaceous magmatic rocks, southern Saqqez, northwestern Iran

Geochemistry ◽

10.1016/j.chemer.2020.125687 ◽

2020 ◽

pp. 125687

Author(s):

Somayeh Gholipour ◽

Hossein Azizi ◽

Fariborz Masoudi ◽

Yoshihiro Asahara ◽

Motohiro Tsuboi

Keyword(s):

Early Cretaceous ◽

Isotope Ratios ◽

Nd Isotope ◽

Magmatic Rocks ◽

Northwestern Iran

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The role of lower continental crust and lithospheric mantle in the genesis of Plio–Pleistocene volcanic rocks from Sardinia (Italy)

Earth and Planetary Science Letters ◽

10.1016/s0012-821x(00)00185-0 ◽

2000 ◽

Vol 180 (3-4) ◽

pp. 259-270 ◽

Cited By ~ 55

Author(s):

Michele Lustrino ◽

Leone Melluso ◽

Vincenzo Morra

Keyword(s):

Continental Crust ◽

Lithospheric Mantle ◽

Volcanic Rocks ◽

Lower Continental Crust

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Island Arc Volcanic Rocks and the Upper Continental Crust

Arc Volcano of Japan - Lecture Notes in Earth Sciences ◽

10.1007/978-4-431-53996-4_7 ◽

2011 ◽

pp. 77-102

Author(s):

Takeru Yanagi

Keyword(s):

Continental Crust ◽

Volcanic Rocks ◽

Island Arc ◽

Upper Continental Crust

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K-Ar ages, major and minor element compositions and Sr, Nd isotope ratios of volcanic rocks from the western part of south Sakhalin, USSR.

JOURNAL OF MINERALOGY PETROLOGY AND ECONOMIC GEOLOGY ◽

10.2465/ganko.87.50 ◽

1992 ◽

Vol 87 (2) ◽

pp. 50-61 ◽

Cited By ~ 1

Author(s):

Mitsuo SHIMAZU ◽

Katsuhiko FURUYAMA ◽

Yoshinobu KAWANO ◽

Satoshi OKAMURA ◽

Hiroto OHIRA ◽

...

Keyword(s):

Volcanic Rocks ◽

Minor Element ◽

Isotope Ratios ◽

Nd Isotope ◽

South Sakhalin

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Field relation, geochemistry and origin of the Xinglonggou volcanic rocks in Beipiao area, Liaoning Province (China): Reappraisal on the foundering of lower continental crust of North China Craton

Journal of Asian Earth Sciences ◽

10.1016/j.jseaes.2011.12.008 ◽

2012 ◽

Vol 47 ◽

pp. 35-50 ◽

Cited By ~ 2

Author(s):

Yang Wang ◽

Su-Hua Cheng

Keyword(s):

Continental Crust ◽

North China Craton ◽

North China ◽

Volcanic Rocks ◽

Liaoning Province ◽

Lower Continental Crust ◽

Field Relation

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Cretaceous intrusions in the Commerce Mountain and adjacent areas of southeastern British Columbia and southwestern Alberta

Canadian Journal of Earth Sciences ◽

10.1139/e99-082 ◽

1999 ◽

Vol 36 (12) ◽

pp. 1939-1956 ◽

Cited By ~ 1

Author(s):

R J Goble ◽

S B Treves ◽

V M Murray

Keyword(s):

Continental Crust ◽

Upper Mantle ◽

Normative Data ◽

Volcanic Rocks ◽

Alkali Feldspar ◽

Upper Crust ◽

Metasomatic Alteration ◽

Isotopic Data ◽

Lower Continental Crust ◽

Low Pressures

An older oversaturated monzonitic and a younger undersaturated syenitic suite of Cretaceous igneous rocks are present at Commerce Mountain and adjacent areas of the southern Canadian Rockies. The undersaturated suite consists of foid-bearing alkali feldspar syenite and trachyte, with lesser amounts of phonolite and foid syenite. Normative data indicate a higher degree of undersaturation attributable to the presence of garnet. Sr and Nd isotopic data are consistent with generation of the magma by partial melting of an enriched source in the upper mantle or the lower continental crust; Pb isotopic data are more consistent with a source in the lower continental crust. High Sr and Ba concentrations in analcime-bearing alkali feldspar megacrysts support early crystallization at high pressure. Replacement of the analcime by muscovite suggests emplacement and continued crystallization at shallow depth under low pressures, at which the analcime was unstable. Prior to emplacement in the upper crust, the Commerce Mountain suite evolved in composition from mafic analcime-bearing perthite syenite to felsic analcime-nepheline-bearing perthite syenite to nepheline (micro)monzosyenite and to analcime (micro)syenite compositionally similar to analcime phonolites found in adjacent areas. Extensive metamorphic-metasomatic alteration suggests that Commerce Mountain was a volcanic center, possibly associated with the eruption of the Crowsnest Formation volcanic rocks.

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Geochemistry of late Mesozoic adakites from the Sulu belt, eastern China: magma genesis and implications for crustal recycling beneath continental collisional orogens

Geological Magazine ◽

10.1017/s0016756805001214 ◽

2005 ◽

Vol 143 (1) ◽

pp. 1-13 ◽

Cited By ~ 81

Author(s):

FENG GUO ◽

WEIMING FAN ◽

CHAOWEN LI

Keyword(s):

Trace Element ◽

Continental Crust ◽

Eastern China ◽

Lower Continental Crust ◽

Nd Isotope ◽

Late Mesozoic ◽

Crustal Recycling ◽

The North ◽

Mantle Peridotites ◽

Collisional Orogens

Both low-Al and high-Al adakitic andesites erupted at ∼ 114 Ma in the Sulu collisional belt, eastern China, provide evidence for recycling of continental crust into the mantle more than 100 million years after the Triassic (∼ 240 Ma) collision between the North China and Yangtze blocks. These rocks display similar normalized trace element patterns, with enrichments in large ion lithophile elements (LILE), light rare earth elements (LREE) and depletions in Nb, Ta and Ti, and have highly radiogenic Sr and non-radiogenic Nd isotopic compositions (high-Al: 87Sr/86Sr(i)=0.70645–0.70715 and εNd(t)=−20.1 to −19.1; low-Al: 87Sr/86Sr(i)=0.70593–0.70598 and εNd(t)=−17.1 to −15.8). The high-Al (Al2O3 > 15 %) adakitic andesites are compositionally comparable with experimental slab melts, whereas the low-Al series (Al2O3 ∼ 13 %) have higher MgO, Cr and Ni, and higher Sr/Y ratios, and are compositionally comparable with slab melts hybridized by mantle peridotites. Combined major- and trace-element and Sr–Nd isotope data indicate that the two types of adakitic andesites have been derived from a LILE- and LREE-enriched eclogitic lower continental crust; in the case of the high-Al adakitic andesites, the melts underwent insignificant mantle contamination, whereas the low-Al magmas reacted with peridotites. Generation of the two types of late Mesozoic adakitic andesites favours a model of lithospheric delamination, leading to asthenospheric upwelling and extensive melting of lower continental crust, including a delaminated block, in the Sulu belt.

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