Late Cretaceous magmatism in Mamba area, central Lhasa subterrane: Products of back-arc extension of Neo-Tethyan Ocean?

Meng, Fanchao; Zhao, Zhidan; Zhu, Di‐Cheng; Mo, Xuanxue; Guan, Qı; Huang, Yennun; Dong, Guochen; Zhou, Shuhua; DePaolo, Donald J.; Harrison, T. Mark; Zhang, Zhaochong; Liu, Junlai; Liu, Yongsheng; Hu, Zhaochu; Yuan, Huan

doi:10.1016/j.gr.2013.07.017

Cited by 52 publications

(32 citation statements)

References 105 publications

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“…Thus the increase of source depth and decrease in magma temperature possibly indicates a decrease in the geothermal gradient which could be related to gradually crustal thickening. The distribution of stage-2 adakitic rocks suggests that the southern Lhasa terrane (Wen et al, 2008a;Guan et al, 2010; this study) and central Lhasa terrane (e.g., Mamba, Meng et al, 2010Meng et al, , 2014 would have a thickened crust. Due to the continuous reducing of geothermal gradient generated by crustal thickening, the magmatism was waning that finally ceased (Fig.…”

Section: Geochemical Constraints On Late Cretaceous Crustal Thickeningmentioning

confidence: 54%

The Gangdese magmatic constraints on a latest Cretaceous lithospheric delamination of the Lhasa terrane, southern Tibet

Chung

et al. 2014

Lithos

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Section: Geochemical Constraints On Late Cretaceous Crustal Thickeningmentioning

confidence: 54%

The Gangdese magmatic constraints on a latest Cretaceous lithospheric delamination of the Lhasa terrane, southern Tibet

Chung

et al. 2014

Lithos

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“…Previous studies proposed different types of subduction models (e.g., flat and steep oceanic slab subduction, oceanic ridge subduction, and rollback of subducted oceanic slab) to account for the early Late Cretaceous (ca. 100–80 Ma) magmatism [e.g., Chung et al , ; Coulon et al , ; DeCelles et al , ; Jiang et al , ; Kapp et al , , ; Ma et al , , ; Meng et al , , ; Wen et al , ; Yin and Harrison , ; Zhang et al , , ; Zhu et al , , ].…”

Section: Discussionmentioning

confidence: 99%

“…Secondly, subduction of a spreading ridge that is subparallel to the trench is likely to cease because of the dominance of young buoyant oceanic crust [e.g., Thorkelson , ]. Moreover, the inferred distance between the trench, and possible oceanic ridge subduction, and a developing back‐arc is not consistent with spreading ridge subduction [ Meng et al , ].…”

Section: Discussionmentioning

confidence: 99%

Late Cretaceous back‐arc extension and arc system evolution in the Gangdese area, southern Tibet: Geochronological, petrological, and Sr‐Nd‐Hf‐O isotopic evidence from Dagze diabases

Wang

Wyman

et al. 2015

JGR Solid Earth

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Back‐arc extension and asthenosphere upwelling associated with oceanic lithospheric subduction affect the structure and thermal regime of the arc lithosphere, which often triggers widespread extension‐related mafic magmatism. Although it is commonly accepted that the Neo‐Tethyan oceanic lithosphere subducted beneath the southern Lhasa block, resulting in the well‐known Late Mesozoic Gangdese magmatic arc, the possible role of contemporary back‐arc extension and asthenosphere upwelling has been disputed due to a lack of evidence for extension‐related mafic magmatism. Here, we report detailed petrological, geochronological, geochemical, and Sr‐Nd‐Hf‐O isotopic data for the Dagze diabases located in the north of the Gangdese district, southern Lhasa block. The zircon U‐Pb analyses indicate that they were generated in the Late Cretaceous (ca. 92 Ma) instead of the Eocene (42–38 Ma) as previously believed. These mafic rocks are characterized by variable MgO (4.0–12.2 wt %) and Mg# (42 to 71) values combined with flat to slightly enriched ([La/Yb]N = 1.87–5.23) light rare earth elements (REEs) and relative flat heavy REEs ([Gd/Yb]N = 1.36–1.87) with negative Ta, Nb, and Ti anomalies (e.g., [Nb/La]PM = 0.16–0.51). They also have slightly variable εNd(t) (−1.25 to +4.71) and low initial 87Sr/86Sr (0.7045–0.7058) values with strong positive igneous zircon εHf(t) (+8.0 to +12.1) and low δ18O (5.31–6.12‰) values. The estimated primary melt compositions are similar to peridotite‐derived experimental melts. Given their high melting temperature (1332 to 1372°C) and hybrid geochemical characteristics, we propose that the Dagze mafic magmas likely represent mixtures of asthenospheric and enriched lithospheric mantle‐derived melts that underwent minor crustal assimilation and fractional crystallization of clinopyroxene. Taking into account the spatial and temporal distribution of Mesozoic mafic‐felsic magmatic rocks and regional paleomagnetic and basin data, we suggest that the Dagze mafic rocks resulted from asthenospheric upwelling associated with intracontinental back‐arc extension during the rollback of subducted Tethyan oceanic lithosphere in the Late Cretaceous.

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“…Meng et al (2014) have demonstrated robustly the existence of magma mixing in terms of whole-rock components and isotope data. This can be further inferred by the following lines of evidence in terms of mineralogy.…”

Section: Mineralogical Evidence For Magma Mixingmentioning

confidence: 86%

“…2h; sample MB09-10). The dioritic MMEs are characterized by high-K calc-alkaline to shoshonitic series, with relatively low content of SiO 2 , K 2 O and high abundance of MgO and Na 2 O (Meng et al, 2014(Meng et al, , 2010. All the mafic enclaves are metaluminous (A/CNK=0.74-0.84; Meng et al, 2014).…”

Section: Mmesmentioning

confidence: 99%

Mineral chemistry and crystallization conditions of the Late Cretaceous Mamba pluton from the eastern Gangdese, Southern Tibetan Plateau

Scheltens

et al. 2016

J. Earth Sci.

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The Late Cretaceous Mamba granodiorite belongs to a part of the Mesozoic Gangdese continental magmatic belt. No quantitative mineralogical study has been made hitherto, and hence the depth at which it formed is poorly constrained. Here we present mineralogical data for the Mamba pluton, including host rocks and their mafic microgranular enclaves (MMEs), to provide insights into their overall crystallization conditions and information about magma mixing. All amphiboles in the Mamba pluton are calcic, with B (Ca+Na)>1.5, and Si=6.81-7.42 apfu for the host rocks and Si=6.77-7.35 apfu for the MMEs. The paramount cation substitutions in amphibole include edenite type and tschermakite type. Biotites both in the host rocks and the MMEs collectively have high MgO (13.19 wt.%-13.03 wt.%) contents, but define a narrow range of Al apfu (atoms per formula unit) variations (2.44-2.57). The oxygen fugacity estimates are based on the biotite compositions cluster around the NNO buffer. The calculated pressure ranges from 1.2 to 2.1 kbar according to the aluminum-in-hornblende barometer. The computed pressure varies from 0.9 to 1.3 kbar based on the aluminum-in-biotite barometer which corresponds to an average depth of ca. 3.9 km. Besides, the estimates of crystallization pressures vary from 0.8 to 1.4 kbar based on the amphibole barometer proposed by Ridolfi et al. (2010), which can be equivalent to the depths ranging from 3.1 to 5.2 km. The MMEs have plagioclase oscillatory zonings and quartz aggregates, probably indicating the presence of magma mixing. Besides, core-to-rim element variations (Rb, Sr, Ba, and P) for the K-feldspar megacrysts serve as robust evidence to support magma mixing and crystal fractionation. This indicates the significance of the magma mixing that contributes to the formation of K-feldspar megacryst zonings in the Mamba pluton. KEY WORDS: Mamba pluton, Gangdese terrane, MMEs, K-feldspar megacrysts, magma mixing, P-T conditions, oxygen fugacity, in-situ trace element. INTRODUCTIONPrevious studies have demonstrated that the composition and structure of feldspar, biotite and amphibole in felsic rocks can serve as ideal proxies for physico-chemical conditions of magmas, such as crystallization and emplacement temperature, pressure, oxygen fugacity, water activity and compositional variations (Ayati et al.

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Late Cretaceous magmatism in Mamba area, central Lhasa subterrane: Products of back-arc extension of Neo-Tethyan Ocean?

Cited by 52 publications

References 105 publications

The Gangdese magmatic constraints on a latest Cretaceous lithospheric delamination of the Lhasa terrane, southern Tibet

The Gangdese magmatic constraints on a latest Cretaceous lithospheric delamination of the Lhasa terrane, southern Tibet

Late Cretaceous back‐arc extension and arc system evolution in the Gangdese area, southern Tibet: Geochronological, petrological, and Sr‐Nd‐Hf‐O isotopic evidence from Dagze diabases

Mineral chemistry and crystallization conditions of the Late Cretaceous Mamba pluton from the eastern Gangdese, Southern Tibetan Plateau

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