Geochemistry of limestones deposited in various plate tectonic settings

Abstract

Limestone, a major part of the global sedimentary succession, susceptible to post-depositional diagenesis. Studies of limestone geochemistry are essential in the discrimination of tectonic settings of basins in which the limestones were deposited. Six Late Mesozoic and one Tertiary limestone successions of Tibet, western China, that were deposited in oceanic plateau, passive continental margin, active continental margin (fore-arc basin, back-arc basin and foreland basin) and continental inland freshwater basins were analyzed for their major, trace and rare earth element (REE) composition. This geochemical dataset, in combination with the Deep Sea Drilling

Provenance of newly discovered Upper Ordovician black rock units in the West Kunlun Orogen, China: Constraints from detrital zircon U–Pb chronology and whole‐rock geochemistry

“…The good correlations between the CIA and the K/Al and Rb/Al ratios (Figure ) suggest that humid and warm climate conditions during the deposition of the black rock units in the West Kunlun Orogen have contributed more fresh water and fine‐grained clay mineral input. The conclusion of humid and warm climate condition is also generally consistent with the lithostratigraphic observation that the limestones are intercalated with the black siliciclastic rocks (Figure d), which is usually considered to form in a warm environment (Zhang, Li et al, ). However, other associated lines of evidence from sedimentology and lithostratigraphy failed to be observed, likely because these sedimentological and lithostratigraphic relicts in the siliciclastic rocks could have been obliterated or blurred by the greenschist‐facies metamorphism (Figure f).…”

“…Trace elements such as Sc, Co, Th, Zr, and Hf are relatively inert elements that are less affected by weathering, transportation, and diagenesis. Their characteristics can serve as a good tracer of sedimentary provenance types and tectonic settings of a basin (Bhatia, ; Bhatia & Crook, ; Zhang, ; Zhang et al, ; Zhang, Zhang, et al, , Zhang, Li, & Wei, , Zhang, Li et al, ). Most black shales exhibit similar Upper Continental Crust (UCC)‐normalized trace element patterns for most LILEs (large‐ion lithophile elements) and HFSEs (high‐field‐strength elements; Figure ).…”

“…The geochemical characteristics of clastic rocks can not only reflect the rock composition of provenance but also imply the sedimentary and tectonic settings (Bhatia, ; Bhatia & Crook, ; Zhang, ; Zhang et al, , Zhang, Zhang, et al, , Zhang, Li, & Wei, , Zhang, Li, et al, ). In the plots of SiO 2 to K 2 O/Na 2 O and K 2 O/Na 2 O to SiO 2 /Al 2 O 3 (Figure a,b), the shale samples scatter across the fields of active continental margin (ACM) and passive margin (PM).…”

Comment on “Sedimentary and Tectonic Evolution of the Southern Qiangtang Basin: Implications for the Lhasa‐Qiangtang Collision Timing” by A. Ma et al.

“…A wealth of studies reveal that marine sedimentation occurred during the Late Jurassic through the Middle Cretaceous (Guo et al, ; Sun & Xu, ; XBGMR (Xizang Bureau of Geology and Mineral Resources), ; Zhang, , ; Yi et al, ; Li & Batten, ; Zhang et al, , , , , ; Y. X. Zhang et al, , and references therein). For example, the turbidite association along the middle‐western Bangong suture, represented by the Muggangri Group, was accumulated throughout the Jurassic (XBGMR (Xizang Bureau of Geology and Mineral Resources), ).…”

Early Cretaceous arc granitoids from the central Lhasa subterrane: Production of the northward subduction of Yarlung Zangbo Neo‐Tethyan Ocean?

“…The Tibetan–Himalayan Plateau formed by successive accretion, from north to south, of the Qaidam, Songpan–Ganzi, Qiangtang, Lhasa, and Indian blocks to the southernmost margin of the Eurasian continent (Figure a). These blocks are separated by the Jinsha Suture Zone (JSZ), Bangong–Nujiang Suture Zone (BNSZ), and Indus–Yarlung Zangbo Suture Zone (IYZSZ), representing Paleo‐, Meso‐, and Neo‐Tethyan oceanic relicts, respectively (Figure a; Li et al, ; Metcalfe, ; Pan et al, ; Yin & Harrison, ; Zhang et al, ; Zhang et al, ; Zhang, Li, Yan, et al, ; Zhang, Zhang, Tang, & Xia, ; Zhu et al, , ; Zhu, Wang, Cawood, Zhao, & Mo, ). The Lhasa Terrane in southern Tibet is the continental block last accreted to Eurasia in the Cretaceous (Zhang, , ; Zhang, Xia, Wang, Li, & Ye, ; Zhang, Zhang, Li, & Zhong, ; Zhang, Zhang, et al, ) before its collision with the northern drifting Indian continent in the Early Cenozoic (Hu et al, ; Zhu et al, ) and marked by large amounts of magmatism, which was named Gandese magmatic arc (Figure b; Huang, Xu, Chen, et al, ; Huang, Xu, et al, ; Pan et al, ; Zhang, , ; Zhang et al, , ; Zhang, Zhang, et al, ; Zhu et al, ; and references therein) and was divided into southern, central, and northern subterranes (SL, CL, and NL) by the Luobadui‐Milashan Fault (LMF) and Shiquan River‐Nam Tso Mélange Zone (SNMZ), respectively (Figure b; Li et al, ; Zhu et al, ).…”