More Like this

1. Lower Crustal Rheology Controls Strain Partitioning and Mode of Intracontinental Deformation

   https://doi.org/10.1029/2023TC007748  

   Xu, Xi; Zuza, Andrew V.; Yin, An; Yu, Peng; Chen, Zhiyong; Zhao, Chongjin; Wang, Baodi; Chen, Hanlin; Lin, Xiubin; Wu, Lei; et al (November 2023, Tectonics)

   Abstract The factors that control strain partitioning along plate boundaries and within continental interiors remains poorly resolved. Plate convergence may be accommodated via distributed crustal shortening or discrete crustal‐scale strike‐slip faulting, but what controls these differing modes of deformation is debated. Here we address this question by examining the actively deforming regions that surround the Tarim Basin in central Asia, where deformation is uniquely partitioned into predominately strike‐slip faults in the east and distributed fold‐thrust belts in the west to accommodate Cenozoic India‐Asia plate convergence. We present integrated geological and geophysical observations to elucidate patterns in crustal deformation and compositional structure in and around the Tarim Basin. The thrust‐dominated western Tarim Basin correlates with a strongly‐magnetic lower crust, whereas strike‐slip faulting along the eastern margins of the Tarim Basin lack such magnetic signals. We suggest that the lower crust of the western Tarim is more mafic and stronger than in the east, which impacts intra‐plate strain partitioning. A stronger lower crust results in vertical decoupling to drive mid‐crust horizontal detachments and facilitate thrust faulting, whereas a more homogenized crust favored vertical transcrustal strike‐slip faulting. These rheological differences likely originated from the impingement of the Permian Tarim plume focused in the west. A comparison with the Longmen Shan of eastern Tibetan Plateau reveals remarkably similar strain partitioning that correlates with variations in foreland rheology. Our results highlight how variations in lower‐crust viscosity impact strain partitioning in an intra‐plate setting and how plume processes exert a strong control on later continental tectonic processes. 

   more » « less
2. Multicyclic Phanerozoic orogeny recorded in the Qaidam continent, northern Tibet: Implications for the tectonic evolution of the Tethyan orogenic system

   https://doi.org/10.1130/B37906.1  

   Wu, Chen; Zhao, Yonghui; Li, Jie; Liu, Wenyou; Zuza, Andrew V; Haproff, Peter J; Ding, Lin (October 2024, Geological Society of America Bulletin)

   The growth and evolution of the Eurasian continent involved the progressive closure of major ocean basins during the Phanerozoic, including the Tethyan and Paleo-Asian oceanic realms. Unraveling this complicated history requires interpreting multiple overprinted episodes of subduction-related magmatism and collisional orogeny, the products of which were later affected by the Cenozoic construction of the Himalayan-Tibetan orogen due to the India-Asia collision. In particular, the tectonic evolution of northern Tibet surrounding the Cenozoic Qaidam Basin is poorly resolved due to several phases of Phanerozoic orogeny that have been reactivated during the Cenozoic deformation. In this study, we investigated the geology of the northern Qaidam continent, which experienced Paleozoic–Mesozoic tectonic activity associated with the development of the Eastern Kunlun orogen to the south and the Qilian orogen to the north. We combined new and published field observations, geochronologic and thermochronologic ages, and geochemical data to construct regional tectonostratigraphic sections and bracket phases of Paleozoic–Mesozoic magmatism associated with oceanic subduction and continental collision. Results suggest that the Qaidam continent experienced two major phases of subduction magmatism and collision. First, a Cambrian–Ordovician magmatic arc developed in the northern Qaidam continent due to south-dipping subduction. This phase was followed by the closure of the Qilian Ocean and the collision of the North China craton and Qaidam continent, resulting in Silurian–Devonian orogeny and the development of a regional unconformity across northern Tibet. A subsequent Permian–Triassic magmatic arc developed across the northern Qaidam continent due to north-dipping subduction. This phase was followed by the closure of the Neo-Kunlun Ocean and the collision of the Songpan Ganzi terrane in the south and Qaidam continent. These interpretations are incorporated into a new and comprehensive model for the Phanerozoic formation of northern Tibet and the Eurasia continent. 

   more » « less
3. Phanerozoic cratonization by plume welding

   https://doi.org/10.1130/G50615.1  

   Xu, Xi; Chen, Hanlin; Zuza, Andrew V.; Yin, An; Yu, Peng; Lin, Xiubin; Zhao, Chongjin; Luo, Juncheng; Yang, Shufeng; Wang, Baodi (January 2023, Geology)

   Deformation-resistant cratons comprise >60% of the continental landmass on Earth. Because they were formed mostly in the Archean to Mesoproterozoic, it remains unclear if cratonization was a process unique to early Earth. We address this question by presenting an integrated geological-geophysical data set from the Tarim region of central Asia. This data set shows that the Tarim region was a deformable domain from the Proterozoic to early Paleozoic, but deformation ceased after the emplacement of a Permian plume despite the fact that deformation continued to the north and south due to the closure of the Paleo-Asian and Tethyan Oceans. We interpret this spatiotemporal correlation to indicate plume-driven welding of the earlier deformable continents and the formation of Tarim’s stable cratonic lithosphere. Our work highlights the Phanerozoic plume-driven cratonization process and implies that mantle plumes may have significantly contributed to the development of cratons on early Earth. 

   more » « less
4. Differences between the central Andean and Himalayan orogenic wedges: A matter of climate

   DeCelles, Peter G; Carrapa, Barbara (May 2023, Earth and Planetary Science Letters)

   The Central Andean and Himalayan orogenic belts provide an ideal natural experiment to test the potential role of climate in controlling orogeny. Approximately equal in age and along-strike length, both orogenic wedges are forming in plate-marginal convergent tectonic settings: The Andes in a retroarc setting and the Himalaya in a collisional setting against the Tibetan backstop. The Central Andes orogenic wedge is volumetrically and aerially nearly two times larger than the Himalayan orogenic wedge, despite the Himalaya having accommodated two to three times more tectonic shortening. The Himalaya exports at least four times more sediment owing to much greater erosion rates as signified by widespread Cenozoic metamorphic rocks and very young (<10 Ma) low-temperature thermochronologic ages. The Central Andes are thermochronologically old (mostly >20 Ma), have no exposures of Cenozoic metamorphic rocks, and are mantled by volcanic and sedimentary rocks, attesting to shallow, slow erosion. We conclude that greater intensity of the Indian Monsoon relative to the South American Monsoon since Oligocene time accounts for the differences in orogen size and characteristics. When viewed as an orogenic wedge that has developed largely after formation of the Tibetan orogenic collage, the Himalaya is neither the largest nor hottest among Earth’s orogens. 

   more » « less
5. Constraints on the timing of the India‐Asia collision and unroofing history of the Himalayan orogen using detrital zircon U‐Pb‐Hf and whole‐rock Sr‐Nd isotopes in Cretaceous‐Miocene Lesser Himalayan sedimentary rocks

   https://doi.org/10.1111/bre.12742  

   Feng, Wei; Meng, Qingquan; Song, Chunhui; Fang, Xiaomin; Zhuang, Guangsheng; He, Pengju; Yang, Shufen; Zhang, Jing; Chen, Yongfa; Zhang, Yihu (December 2022, Basin Research)

   Abstract Cretaceous‐Miocene sedimentary rocks in the Nepalese Lesser Himalaya provide an opportunity to decipher the timing of India‐Asia collision and unroofing history of the Himalayan orogen, which are significant for understanding the growth processes of the Himalayan‐Tibetan orogen. Our new data indicate that detrital zircon ages and whole‐rock Sr‐Nd isotopes in Cretaceous‐Miocene Lesser Himalayan sedimentary rocks underwent two significant changes. First, from the Upper Cretaceous‐Palaeocene Amile Formation to the Eocene Bhainskati Formation, the proportion of late Proterozoic‐early Palaeozoic zircons (quantified by an index of 500–1200 Ma/1600–2800 Ma) increased from nearly 0 to 0.7–1.4, and the percentage of Mesozoic zircons decreased from ca. 14% to 5–12%. The whole‐rock⁸⁷Sr/⁸⁶Sr and εNd(t = 0) values changed markedly from 0.732139 and −17.2 for the Amile Formation to 0.718106 and −11.4 for the Bhainskati Formation. Second, from the Bhainskati Formation to the lower‐middle Miocene Dumri Formation, the index of 500–1200 Ma/1600–2800 Ma increased to 2.2–3.7 and the percentage of Mesozoic zircons abruptly decreased to nearly 0. The whole‐rock⁸⁷Sr/⁸⁶Sr and εNd(t = 0) values changed significantly to 0.750124 and −15.8 for the Dumri Formation. The εHf(t) values of Early Cretaceous zircons in the Taltung Formation and Amile Formation plot in the U‐Pb‐εHf(t) field of Indian derivation, whereas εHf(t) values of Triassic‐Palaeocene zircons in the Bhainskati Formation demonstrate the arrival of Asian‐derived detritus in the Himalayan foreland basin in the Eocene based on available datasets. Our data indicate that (1) the timing of terminal India‐Asia collision was no later than the early‐middle Eocene in the central Himalaya, and (2) the Greater Himalaya served as a source for the Himalayan foreland basin by the early Miocene. When coupled with previous Palaeocene‐early Eocene provenance records of the Tethyan Himalaya, our new data challenge dual‐stage India‐Asia collision models, such as the Greater India Basin hypothesis and its variants and the arc–continent collision model. 

   more » « less