central tibetan plateau
Recently Published Documents


TOTAL DOCUMENTS

339
(FIVE YEARS 99)

H-INDEX

44
(FIVE YEARS 7)

2021 ◽  
pp. 1-14
Author(s):  
Bin Liu ◽  
You-Jun Tang ◽  
Lü-Ya Xing ◽  
Yu Xu ◽  
Shao-Qing Zhao ◽  
...  

Abstract Primitive lamprophyres in orogenic belts can provide crucial insights into the nature of the subcontinental lithosphere and the relevant deep crust–mantle interactions. This paper reports a suite of relatively primitive lamprophyre dykes from the North Qiangtang, central Tibetan Plateau. Zircon U–Pb ages of the lamprophyre dykes range from 214 Ma to 218 Ma, with a weighted mean age of 216 ± 1 Ma. Most of the lamprophyre samples are similar in geochemical compositions to typical primitive magmas (e.g. high MgO contents, Mg no. values and Cr, with low FeOt/MgO ratios), although they might have experienced a slightly low degree of olivine crystallization, and they show arc-like trace-element patterns and enriched Sr–Nd isotopic composition ((87Sr/86Sr)i = 0.70538–0.70540, ϵNd(t) = −2.96 to −1.65). Those geochemical and isotopic variations indicate that the lamprophyre dykes originated from partial melting of a phlogopite- and spinel-bearing peridotite mantle modified by subduction-related aqueous fluids. Combining with the other regional studies, we propose that slab subduction might have occurred during Late Triassic time, and the rollback of the oceanic lithosphere induced the lamprophyre magmatism in the central Tibetan Plateau.


2021 ◽  
pp. 105931
Author(s):  
Kunxin Wang ◽  
Ning Ma ◽  
Yinsheng Zhang ◽  
Yaohui Qiang ◽  
Yanhong Guo

Geoderma ◽  
2021 ◽  
Vol 400 ◽  
pp. 115083
Author(s):  
Lin Zhao ◽  
Guojie Hu ◽  
Xiaodong Wu ◽  
Tonghua Wu ◽  
Ren Li ◽  
...  

Author(s):  
Yun-Chuan Zeng ◽  
Ji-Feng Xu ◽  
Ming-Jian Li ◽  
Jian-Lin Chen ◽  
Bao-Di Wang ◽  
...  

Abstract Orthopyroxene-bearing granitic rock (e.g., charnockite) is relatively rare but provides an excellent opportunity to probe the thermal and tectonic evolution of deep orogenic crust because of its distinct mineral assemblage. Here we present petrological, mineralogical, elemental, and Sr–Nd–Hf–O isotopic data for late Eocene (ca. 36 Ma; zircon U–Pb ages) volcanic rocks exposed in the Ejiu region in the southern Qiangtang Terrane to investigate how the central Tibetan crust evolved to its modern thickness and thermal state. The Ejiu volcanic rocks (EVRs) are trachydacites with anhydrous mineral assemblages (i.e., two pyroxenes, sanidine, plagioclase, and ilmenite, without amphibole and biotite) and geochemical characteristics (e.g., high P2O5 and TiO2) that resemble those of charnockite-type magmatic rocks. Mineral and whole-rock thermometry and hygrometry suggests that the parent magma crystallized under hot (~1000 °C) and dry (H2O < 2 wt.%) condition. Besides, the EVRs display adakitic affinities according to their high SiO2 and Al2O3 contents, high Sr/Y, La/Yb, and Gd/Yb ratios, and low Y and Yb contents, without marked negative Eu anomalies. The calculated melts in equilibrium with pyroxenes also display adakitic compositions (e.g., high Sr/Y and La/Yb ratios), indicating that the adakitic compositions of the EVRs did not result from late-stage magmatic evolution. In addition, the melts of the EVRs were saturated in TiO2, as inferred from the high TiO2 contents of these rocks and the presence of ilmenite. An integrated analysis of the geochemical, petrological, and mineralogical data suggests that the EVRs were neither evolutional products nor partial melts of hydrous mafic materials at normal crustal pressures, but were formed by fusion of an eclogitized mafic protolith with residue containing garnet and rutile but lacking amphibole and plagioclase. The whole-rock Sr–Nd and zircon Hf isotope compositions of the EVRs [(87Sr/86Sr)i = 0.7053 to 0.7066; εNd(t) = −1.40 to −0.99; zircon εHf(t) = +1.08 to +5.31] indicate that the parental protolith was relatively juvenile in nature, but also contained some supracrustal materials given the high zircon δ18O values [zircon δ18O = +8.21‰ to +11.00‰]. The above arguments lead us to propose that of partial melting of a previously dehydrated—but chemically undepleted—mafic lower continental crust at high pressure (>1.5 GPa) and high temperature (>1000 °C) generated the EVRs. Based on a synthesis of independent geological and geophysical data, we further suggest that the southern Qiangtang Terrane crust of the central Tibetan Plateau was thick, dry, and elevated during the Late Cretaceous to early Eocene time, and that it became abnormally hot owing to the ascending asthenosphere after lithospheric foundering during the middle Eocene.


2021 ◽  
Vol 9 ◽  
Author(s):  
Lan Luo ◽  
Zhongping Lai ◽  
Wenhao Zheng ◽  
Yantian Xu ◽  
Lupeng Yu ◽  
...  

When and how was the Tibetan Plateau (TP), one of the least habitable regions on Earth, occupied by humans are important questions in the research of human evolution. Among tens of Paleolithic archaeological sites discovered over the past decades, only five are considered coeval with or older than the Last Glacial Maximum (LGM, ∼27–19 ka). As one of them, the Siling Co site in the central TP was previously announced to be ∼40–30 ka based on radiocarbon dating and stratigraphic correlation. Given the loose chronological constraint in previous studies, we here re-examined the chronology of the Siling Co site with the optically stimulated luminescence (OSL) dating technique. Four sections from the paleo-shoreline at an elevation of ∼4,600 m in southeastern Siling Co were investigated, with stone artifacts found from the ground surface. Dating results of nine samples delineated the age of ∼4,600 m paleo-shoreline to be ∼10–7 ka (∼8.54 ± 0.21 ka in average). This age indicates that the Siling Co site is not earlier than the early Holocene, much younger than the former age. The revised age of the Siling Co site is consistent with the wet and humid climate conditions on the TP during the early Holocene.


Sign in / Sign up

Export Citation Format

Share Document