Cambrian volcanism in the Lhasa terrane, southern Tibet: Record of an early Paleozoic Andean-type magmatic arc along the Gondwana proto-Tethyan margin

Accompanying Gondwana assembly, widespread but diachronous Ediacaran−early Paleozoic magmatism of uncertain origin occurred along the supercontinent’s proto-Tethyan margin. We report new geochemical, isotopic, and geochronological data for Cambrian magmatic rocks (ca. 500 Ma) from the Gondwana-derived North Lhasa terrane, located in the present-day central Tibetan Plateau. The magmatic rocks are composed of basalts, gabbros, quartz monzonites, granitoids (with mafic microgranular enclaves), and rhyolites. Nd-Hf isotopic and whole-rock geochemical data indicate that these rocks were probably generated by mixing of mantle-derived mafic and crust-derived felsic melts. The mantle end-member volumes of mafic, intermediate, and felsic rocks are ∼75%−100%, 50%−60%, and 0−30%, respectively. Integration of our new data with previous studies suggests that the North Lhasa terrane experienced long-term magmatism through the Ediacaran to Ordovician (ca. 572−483 Ma), with a magmatic flare-up at ca. 500 Ma. This magmatism, in combination with other Ediacaran−early Paleozoic magmatism along the proto-Tethyan margin, was related to an Andean-type arc, with the magmatic flare-up event related to detachment of the oceanic slab following collisional accretion of Asian microcontinental fragments to northern Gondwana. Diachroneity of the proto-Tethyan arc system along the northern Gondwanan margin (ca. 581−531 Ma along the Arabian margin and ca. 512−429 Ma along the Indian-Australian margin) may have been linked to orogenesis within Gondwana. The North Lhasa terrane was probably involved in both Arabian and Indian-Australian proto-Tethyan Andean-type orogens, based on its paleogeographic location at the northern end of the East African orogen.

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Neoproterozoic and Early Paleozoic magmatism in the eastern Lhasa terrane: Implications for Andean-type orogeny along the northern margin of Rodinia and Gondwana

Precambrian Research ◽

10.1016/j.precamres.2021.106520 ◽

2022 ◽

Vol 369 ◽

pp. 106520

Author(s):

Yanfei Chen ◽

Zeming Zhang ◽

Xuanhua Chen ◽

Richard M. Palin ◽

Zuolin Tian ◽

...

Keyword(s):

Early Paleozoic ◽

Northern Margin ◽

Lhasa Terrane ◽

Andean Type

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High density carbonic fluids in a slab window: Evidence from the Gangdese charnockite, Lhasa terrane, southern Tibet

Journal of Asian Earth Sciences ◽

10.1016/j.jseaes.2011.03.017 ◽

2011 ◽

Vol 42 (3) ◽

pp. 515-524 ◽

Cited By ~ 31

Author(s):

Zeming Zhang ◽

Kun Shen ◽

M. Santosh ◽

Xin Dong

Keyword(s):

High Density ◽

Southern Tibet ◽

Lhasa Terrane ◽

Slab Window

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Late Cretaceous tectonothermal evolution of the southern Lhasa terrane, South Tibet: Consequence of a Mesozoic Andean-type orogeny

Tectonophysics ◽

10.1016/j.tecto.2018.03.001 ◽

2018 ◽

Vol 730 ◽

pp. 100-113 ◽

Cited By ~ 2

Author(s):

Xin Dong ◽

Ze-ming Zhang ◽

Reiner Klemd ◽

Zhen-yu He ◽

Zuo-lin Tian

Keyword(s):

Late Cretaceous ◽

Lhasa Terrane ◽

Andean Type ◽

South Tibet

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Early Carboniferous Back‐Arc Rifting‐Related Magmatism in Southern Tibet: Implications for the History of the Lhasa Terrane Separation From Gondwana

Tectonics ◽

10.1029/2020tc006237 ◽

2020 ◽

Vol 39 (10) ◽

Author(s):

Xuhui Wang ◽

Xinghai Lang ◽

Juxing Tang ◽

Yulin Deng ◽

Qing He ◽

...

Keyword(s):

Early Carboniferous ◽

Southern Tibet ◽

Lhasa Terrane ◽

History Of ◽

Back Arc

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Magmatic record of continuous Neo-Tethyan subduction after initial India-Asia collision in the central part of southern Tibet

Geological Society of America Bulletin ◽

10.1130/b35444.1 ◽

2020 ◽

Author(s):

Feng Huang ◽

Tyrone O. Rooney ◽

Ji-Feng Xu ◽

Yun-Chuan Zeng

Keyword(s):

Mantle Wedge ◽

Leading Edge ◽

Continental Collision ◽

Southern Tibet ◽

Mafic Rocks ◽

Lhasa Terrane ◽

Slab Breakoff ◽

Geodynamic Processes ◽

Generation Mechanisms ◽

Transitional Phase

The Lhasa Terrane in southern Tibet is the leading edge of the Tibet-Himalaya Orogen and represents a fragmentary record of terminal oceanic subduction. Thus, it is an ideal region for studying magmatism and geodynamic processes that occurred during the transition from oceanic subduction to continental collision and/or oceanic slab breakoff. Here we examine a suite of early Cenozoic mafic rocks (ca. 57 Ma) within the central part of Lhasa Terrane, southern Tibet, which erupted during a transitional phase between the onset of India-Asia continental collision and Neo-Tethyan slab breakoff. These rocks display a geochemical affinity with magmas produced by fluid-fluxed melting of the mantle wedge within a subduction zone environment. The whole-rock element and Sr-Nd isotope compositions of these mafic rocks are similar to those of Cretaceous subduction-related magmatism in southern Tibet, demonstrating the sustained influence of the Neo-Tethys Ocean slab on the mantle wedge during the onset of the collision of India and Asia. The results of our geochemical forward modeling constrain the conditions of melt generation at depths of 1.3−1.5 GPa with significant fluid additions from the Neo-Tethyan slab. These results provide the first petrological and geochemical evidence that slab flux-related magmatism continued despite the commencement of continental collision. While existing studies have suggested that magmas were derived from melting of the Neo-Tethyan slab during this period, our new results suggest that additional magma generation mechanisms were active during this transitional phase.

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Appalachian Orogen in Canada

Canadian Journal of Earth Sciences ◽

10.1139/e79-070 ◽

1979 ◽

Vol 16 (3) ◽

pp. 792-807 ◽

Cited By ~ 351

Author(s):

Harold Williams

Keyword(s):

Continental Margin ◽

Eastern North America ◽

Early Paleozoic ◽

The West ◽

Late Precambrian ◽

Northwest Africa ◽

Iapetus Ocean ◽

History Of ◽

Appalachian Orogen ◽

Andean Type

The Appalachian Orogen is divided into five broad zones based on stratigraphic and structural contrasts between Cambrian–Ordovician and older rocks. From west to east, these are the Humber, Dunnage, Gander, Avalon, and Meguma Zones.The westerly three zones fit present models for the development of the orogen through the generation and destruction of a late Precambrian – Early Paleozoic Iapetus Ocean. Thus, the Humber Zone records the development and destruction on an Atlantic-type continental margin, i.e., the ancient continental margin of Eastern North America that lay to the west of Iapetus; the Dunnage Zone represents vestiges of Iapetus with island arc sequences and mélanges built upon oceanic crust; and the Gander Zone records the development and destruction of a continental margin, at least in places of Andean type, that lay to the east of Iapetus.The Precambrian development of the Avalon Zone relates either to rifting and the initiation of Iapetus or to subduction and a cycle that preceded the opening of Iapetus. During the Cambrian Period, the Avalon Zone was a stable platform or marine shelf.Cambrian–Ordovician rocks of the Meguma Zone represent either a remnant of the continental embankment of ancient Northwest Africa or the marine fill of a graben developed within the Avalon Zone.Silurian and younger rocks of the Appalachian Orogen are mixed marine and terrestrial deposits that are unrelated to the earlier Paleozoic zonation of the system. Silurian and later development of the orogen is viewed as the history of deposition and deformation in successor basins that formed across the already destroyed margins and oceanic tract of Iapetus.

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