Detrital Zircon U‐Pb Age Distribution and Hf Isotopic Constraints From the Terrigenous Sediments of the Song Chay Suture Zone (NE Vietnam) and Their Paleogeographic Implications on the Eastern Paleo‐Tethys Evolution

Abstract

The location of the suture zone between the South China Block (SCB) and the Indochina Block (IB) is disputed. Recently, along the Song Chay (Chay river) belt, a mélange zone was proposed as a potential suture zone of the SCB and IB. However, the provenance and age of the Song Chay mélange is poorly known. In order to better constrain the age and provenance of the elements forming the Song Chay mélange, nine samples of detrital material, and one orthogneiss were subjected to zircon U‐Pb and Hf isotope analysis. Detrital zircons from the silty matrix of the Song Chay mélange record three major Neoproterozoic age clusters at 580–650, 700–800, and 900–1,000 Ma, which correspond well to the substratum of the SCB. Two minor Late and Early Paleozoic age groups at 270–330, and 420–500 Ma, with mainly negative εHf(t) values were also recovered. We consider that the zircons in the matrix of the mélange were mainly derived from the subducting plate, namely the SCB. This interpretation is supported by the occurrence of lensoid sandstone blocks, representing the substratum of the SCB, included into the mélange. The deposition age of the Song Chay mélange is between 310 and 250 Ma. Our results demonstrate that in an ophiolitic mélange, the detrital material does not invariably come from the overriding plate, but at the onset of the collision, the subducting continental plate may also supply the terrigenous material.

Detrital zircon U Pb age distributions and Hf isotopic constraints of the Ailaoshan-Song Ma Suture Zone and their paleogeographic implications for the Eastern Paleo-Tethys evolution

“…The different components and provenances of the Song Chay ophiolitic mélange, Song Ma ophiolitic mélange and Ailaoshan ophiolitic mélange suggest a lateral heterogeneity of the Ailaoshan-Song Ma-Song Chay suture. The SCB acted as the main provenance for the Song Chay ophiolitic mélange, which indicates that the Paleo-Tethys ocean in the Song Chay segment was a narrow ocean (Wang et al, 2021). However, the sedimentary cover in IB and the magmatic arc was the main source of the Ailaoshan and Song Ma ophiolitic mélanges, except the M2 unit, limited detrital zircons were considered to derive from SCB, this may suggest a relatively wide ocean basin separating the SCB and IB.…”

“…14). The provenance of the detrital zircon in the Song Chay mélange was interpreted as mainly from the SCB, with only a very limited amount of Late Paleozoic zircons that might come from the IB (Wang et al,2021). Therefore, we speculate that the differences in the age patterns of detrital zircon in the Song Chay and Ailaoshan-Song Ma ophiolitic mélanges reflect the variety of the sources that supplied the material deposited in the subduction mélange all along the segments of the Ailaoshan-Song Ma-Song Chay suture.…”

“…During this time, along the Song Chay segment, the magmatic arc was less developed, and the SCB (as the passive margin) acted as the main provenance of sediments in the mélange (Figs. 14, 17B;Wang et al, 2021). On the contrary, in the western part of Western Ailaoshan-Truong Son magmatic arc belt (IB), the Upper Permian (Longtan formation), as the sediments of retro-arc basin, contain significant signal of these period (yellow cross in Fig.…”

“…Wang et al (2021) have analyzed the detrital zircons from the matrix of Song Chay ophiolitic mélange. This study revealed that the detrital zircon yields several age peaks from Paleoproterozoic to Late Paleozoic, at 2440 Ma, 1775 Ma, 1560 Ma, 970Ma, 770 Ma, 730 Ma, 620 Ma, 460 Ma, and 310 Ma (Fig.14).…”

Triassic detrital records in the western Dian‐Qiong suture, South China: Implications for the eastern Paleo‐Tethys evolution

“…Yunkai and Wuyi massifs,Faure et al, 2009;Li et al, 2010;Wang et al, 2007Wang et al, , 2011Yu et al, 2018) and NVT (e.g. Song Chay F I G U R E 4 Probability density plots for detrital zircon U-Pb ages from the Middle Triassic turbidite sandstones in the Malipo basin (a-e), compared with those from the early Middle Triassic turbidites in the Song Hien basin, western Dian-Qiong suture (f,Halpin et al, 2016;Wang et al, 2021), the early Middle Triassic turbidites in the Napo basin to the south of the volcanic arc (g, and the Middle Triassic turbidites in the central-northern Nanpanjiang basin to the north of the Napo-Jingxi-Pingxiang volcanic arc (h,Lehrmann et al, 2015;Yang et al, 2012). [Colour figure can be viewed at wileyonlinelibrary.com] , central-northern Nanpanjiang basin (n=1706,Yang et al, 2012;Lehrmann et al, 2015) Triassic turbidites, Song Hien basin (n=154,Halpin et al, 2016;Wang et al, 2021 Wang et al, ) et al, 2000Yan et al, 2006).…”