Contemporaneous east–west extension and north–south compression at 43 Ma in the Himalayan orogen

Abstract

It was previously proposed that the onset of east-west extension in the Himalayan orogen occurred after ca. 19 Ma. Here we present a Re-Os isochron age of ca. 43 Ma for sulfides from the Zhaxikang Zn-Pb-Sb-Ag polymetallic deposits, which occur within N-S-striking normal faults that reflect E-W extension in the Tethyan Himalayan orogen. This age is consistent with previously reported ages for regional metamorphism (ca. 48-42 Ma), granitoids (ca. 47-40 Ma) and gabbros (ca. 45 Ma) occurring along the Indus-Yarlung suture. In addition, this type of structure also broadly occurs in the Lhasa terrane, and plays a critical role in the Eocene porphyry-(skarn) copper polymetallic mineralization there. By ca. 45-43 Ma, the north-south-directed horizontal deviatoric stresses had peaked and subducted Neo-Tethyan slab breakoff had occurred at great depth, leading to abrupt slowdown of Indo-Asia convergence (ca. 45 Ma). E-W extension initially developed at shallow depths, resulting in formation of the north-south trending normal faults in the plateau. This type of extension would lead to collapse of the Tibetan plateau and decrease in altitude, subsequently resulted in Central Asian and the global climate changes. Our study places new constraints on the timing and nature of early Cenozoic tectonics and metallogenesis in the Himalayan orogen and climate changes in Central Asia.

A timeline of the Cenozoic tectonic–magmatic–metamorphic evolution and development of ore resources in the Himalayas

“…The geochronological results of the metallogenic timing of the largest‐scale Zhaxikang lead–zinc–antimony–gold deposit in the Himalayas span the Eocene–Oligocene–Miocene epochs. Sulfide Re–Os isotopes from this deposit have three sets of ages of 47.7 ± 7.9 Ma (Wang et al, 2019), 43.1 ± 2.5 Ma (Zhou, Sun, et al, 2018) and 9.0 ± 1.9 Ma (Wang et al, 2019) and sericite Ar–Ar isotopes also occur in three age groups, 19.3 ± 1.1 Ma (Sun et al, 2018), 16.0 ± 0.3 Ma (Zhang, Li, Zhang, et al, 2020) and 11.7 ± 3.1 Ma (Liang et al, 2015). In addition, the sericite Ar–Ar ages of the Keyue lead–zinc deposit and the Jienagepu gold deposit on the north side of the Zhaxikang periphery date to 21.7 ± 0.7 Ma (Lin et al, 2016) and 15 ± 4 Ma (Dong et al, 2017).…”

Distribution patterns of Chinese Cixiidae (Hemiptera, Fulgoroidea), highlight their high endemic diversity

“…A semi-arid zone covers 22%, a semi-humid zone covers 15%, and the humid zone (32%) is located primarily in the southeast of China ( Ge et al 2013 ). Geological complexity of China is also significant, particularly with the uplift of the Qinhai-Tibet Plateau, which occurred in the middle of the Eocene era (45-38 Ma) ( Zhou et al 2018 ). When this complexity is combined with the monsoonal climate evolution, it has created strongly diversified biotopes, isolated by biogeographical barriers that manage dispersal pathways for species, providing new ecological niches, which has driven the recent evolution of plants and animal diversity ( Favre et al 2015 , Liu et al 2017 ).…”