Mid-Neoproterozoic (ca. 830-800 Ma) metamorphicP-Tpaths link Tarim to the circum-Rodinia subduction-accretion system

Abstract

Long‐lived exterior accretionary orogeny shapes tectonothermal evolution of the peripheral building blocks of supercontinents and leads to considerable crustal growth. However, such accretionary orogeny has only been locally recognized for the Rodinia supercontinent. Here a suite of newly discovered mid‐Neoproterozoic high‐grade metamorphic rocks in the northern Tarim Craton, NW China, are used to test the exterior accretion hypothesis for Rodinia. These rocks occur as dark‐colored mafic and calc‐silicate boudins in impure marbles and mica schists. Geochemical data suggest a protolith of arc‐related basalts metasomatized by Ca‐rich fluids. Mineral assemblages, phase diagram modeling, and mineral compositions for a garnet pyroxenite and a garnet clinopyroxene gneiss reveal upper amphibolite to high‐pressure granulite facies peak metamorphism (660–700°C, 11–12 kbar) following a counterclockwise P‐T path, which is characterized by prograde burial and heating, followed by near‐isothermal burial and retrograde exhumation and cooling. This P‐T path is interpreted to have recorded crustal thickening of an earlier magmatic arc transformed to a fore arc by subduction erosion and subsequent burial along bent isotherms near the subduction channel. All studied samples record ca. 830–800 Ma metamorphic zircon U‐Pb ages, which probably date the early exhumation and cooling according to Ti‐in‐zircon temperatures, zircon rare earth element patterns, and Hf isotopes. This is the first mid‐Neoproterozoic P‐T‐t path in Tarim, and it provides metamorphic evidence for a mid‐Neoproterozoic advancing‐type accretionary orogeny, which is coeval with the initial breakup events of Rodinia and thus links Tarim to the circum‐Rodinia accretion system, supporting the peripheral subduction model.

Crustal evolution in the South Tianshan Terrane: Constraints from detrital zircon geochronology and implications for continental growth in the Central Asian Orogenic Belt

“…The Latest Mesoproterozoic and Neoproterozoic tectonic evolution of the Tarim Craton, as well as that of other areas of the northern Xinjiang, was correlated to the assembly and break‐up of the supercontinent Rodinia (e.g., Cawood et al, ; Evans, ; J. Gao et al, ; Ge, Zhu, Wilde, He, et al, ; Ge et al, ; Z. X. Li, Evans, & Halverson, ; Z. Q. Xu et al, ; C. L. Zhang, Zou, et al, ; W. B. Zhu et al, ). Our new results and previous data reveal five pulses of Neoproterozoic magmatism: 995 to 901 Ma (peaked at ~956 Ma), 886 to 752 Ma (peaked at ~823 Ma), 736 to 694 Ma (peaked at ~704 Ma), and 665 to 610 Ma (peaked at ~638 Ma).…”

“…In spite of a large number of investigations, several fundamental aspects of the geology and tectonics of the Tarim Craton and south‐western CAOB remain controversial. For instance, in terms of the mechanism and timescale of the rifting processes in the Tarim Craton during the break‐up of the Neoproterozoic supercontinent Rodinia, opinions are diverse and include the superplume‐model (X. P. Long, Yuan, Sun, Kröner, et al, ; Z. Q. Xu et al, ; C. L. Zhang, Zou, Li, Wang, ) and back‐arc extension model (Ge, Zhu, Wilde, He, et al, ; Ge, Zhu, & Wilde, ). Furthermore, the origin, timescale, and subduction polarity of the Palaeozoic South Tianshan Ocean that existed between the Palaeozoic Tarim and SW CAOB also remain debated.…”

Final Assembly of the Southwestern Central Asian Orogenic Belt as Constrained by the Evolution of the South Tianshan Orogen: Links With Gondwana and Pangea

“…The microcontinents (such as the CTB, KYB, KNTS) in the western CAOB and the Tarim Craton were interpreted to have been incorporated into the periphery of Rodinia through long‐lived subduction‐accretion processes, as evidenced by widespread late Mesoproterozoic to early Neoproterozoic magmatic rocks, and the ~830–790‐Ma Aksu blueschists and HP granulites (Ge, Zhu, Wilde, He, et al, ; Ge et al, ; He et al, ; Kröner et al, , ; Wang, Liu, et al, ). It was further suggested that these microcontinents and the Tarim Craton were detached from peri‐Rodinia by back‐arc rifting or plume‐related breakup (e.g., Gao et al, ; Ge, Zhu, Wilde, He, et al, ; Ge, Zhu, Zheng, et al, ; Zhang, Li, et al, ), leading to the opening of multiple oceanic basins, such as the proto‐Tethys Ocean between the Tarim Craton and northwest Australia (Zhang et al, ), and the South Tianshan, Terskey, and Djalair‐Naiman oceanic basins as the southern branches of the Paleo‐Asian Ocean (Figure ; Gao et al, ; Ge, Zhu, Wilde, He, et al, ).…”

“…Paleozoic strata consist of Cambrian–Ordovician phosphorous siliciclastic and carbonate sequences, Silurian–Devonian shallow‐marine clastic sediments, and Carboniferous–Permian clastic‐carbonates and volcanic beds, which are separated by two major angular unconformities (Carroll et al, ; Han et al, ; Xiao et al, ). Several magmatic and tectonothermal events display Neoarchean to Permian ages, including ~830–790 Ma HP granulite‐facies metamorphism (Ge et al, ; He et al, ), ~780–760 Ma Aksu blueschist‐facies metamorphism (Yong et al, ; Zhang et al, ), and ~460–380 Ma arc‐related plutonic rocks (Ge, Zhu, Wu, et al, ; Ge, Zhu, Wilde, He, et al, ).…”

Provenance and tectonic setting of the Palaeozoic sediments in the northern Alxa area: Implications for the Central Asian Orogenic Belt

“…The response time of the assembly and breakup was variable in different parts of Rodinia, but the Rodinia supercontinent was assembled at ~1.1–1.0 Ga and fragmented at ~0.8–0.7 Ga totally (Rogers & Santosh, ). The Tarim Craton has been broadly accepted to be involved with the assembly and breakup of the Neoproterozoic Rodinia supercontinent (Ge et al, ; Ge, Zhu, & Wilde, ; He, Zhang, Zong, Wang, & Yu, ; Li, Qiu, Chang, & Yang, ; Lu et al, ; Shu, Deng, Zhu, Ma, & Xiao, ; Zhang, Zou, Li, & Wang, ), and the most significant peak age of ~0.8 Ga in the magmatic records of the Tarim Craton is probably associated with the Rodinia supercontinent cycle (Zhang et al, ). This Grenville event (~1.1–0.85 Ga) in the Tarim Craton makes it different from the North China Craton (Lu et al, ; Ma, Shu, Santosh, & Li, ; Rojas‐Agramonte et al, ).…”