Compositions and ages of Early Cretaceous volcanic and plutonic rocks in central Tibet; insights into the magmatic and uplift response to slab breakoff

• Published in: Geosphere (Boulder, Colo.) Colo.), 2023-04, Vol.19 (2), p.583-598
• Main Authors: Wu Hao, Wu Hao, Liu Fei, Liu Fei, Liu Xi-Jun, Liu Xi-Jun, Wu Yan-Wang, Wu Yan-Wang, Li Cai, Li Cai, Yang Rui, Yang Rui
• Format: Article
• Language: English
• Subjects: alkaline earth metals; Asia; China; Cretaceous; crust; Far East; hafnium; Hf-177/Hf-176; igneous and metamorphic rocks; igneous rocks; isotope ratios; isotopes; large-ion lithophile elements; magmatism; mantle; Mesozoic; metals; Petrology; plate collision; plate tectonics; plutonic rocks; Sr-87/Sr-86; stable isotopes; strontium; subduction; trace elements; uplifts; Upper Cretaceous; volcanic rocks; Xizang China
• ISSN: 1553-040X; 1553-040X
• DOI: 10.1130/GES02586.1

We present new zircon U-Pb ages and Hf isotope compositions as well as whole-rock major- and trace-element geochemical and Sr-Nd isotopic data for silicic plutonic and volcanic rocks from the Duolong area of central Tibet. Combined with existing data, our new data indicate that these plutonic and volcanic rocks were formed in two stages ca. 120 Ma and ca. 110 Ma, respectively, in a postcollisional extensional setting that was triggered by slab breakoff. The similar geochemical compositions of granitoids and rhyolites, combined with their close spatial and temporal relationships, suggest that they were both derived from juvenile crustal material within a single magmatic system. We propose that the two inferred crustal melting events in the Duolong area were caused by two episodes of deep mantle activity triggered by the transition of the plate subduction angle from steep to shallow in response to the ascent of buoyant continental lithosphere during slab breakoff. Furthermore, rapid surface uplift during the late Early Cretaceous caused by slab breakoff made an important contribution to the formation of the proto-Tibetan Plateau. This study provides new insights into postcollisional tectonomagmatism and plateau uplift in central Tibet triggered by slab breakoff. We propose more generally that tectonic uplift during postcollisional processes (i.e., slab breakoff and lithospheric delamination) is a major contributor to plateau uplift in collision zones.