Paleo-Pacific subduction-accretion: Evidence from Geochemical and U-Pb zircon dating of the Nadanhada accretionary complex, NE China

Abstract

The Nadanhada Terrane, located along the eastern margin of Eurasia, contains a typical accretionary complex related to paleo-Pacific plate subduction-accretion. The Yuejinshan Complex is the first stage accretion complex that consists of meta-clastic rocks and metamafic-ultramafic rocks, whereas the Raohe Complex forms the main parts of the terrane and consists of limestone, bedded chert, and mafic-ultramafic rocks embedded as olistolith blocks in a weakly sheared matrix of clastic meta-sedimentary rocks. Geochemical data indicate that the Yuejinshan metabasalts have normal mid-ocean ridge basalt (N-MORB) affinity, whereas the Raohe basaltic pillow lavas have an affinity to ocean island basalts (OIB). Sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon analyses of gabbro in the Raohe Complex yield a weighted mean 206 Pb/ 238 U zircon age of 216 ± 5 Ma, whereas two samples of granite intruded into the complex yield weighted mean 206 Pb/ 238 U zircon ages of 128 ± 2 and 129 ± 2 Ma. Laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) U-Pb zircon analyses of basaltic pillow lava in the Raohe Complex define a weighted mean age of 167 ± 1 Ma. Two sandstone samples in the Raohe Complex record younger concordant zircon weighted mean ages of 167 ± 17 and 137 ± 3 Ma. These new data support the view that accretion of the Raohe Complex was between 170 and 137 Ma, and that final emplacement of the Raohe Complex took place at 137-130 Ma. The accretion of the Yuejinshan Complex probably occurred between the 210 and 180 Ma, suggesting that paleo-Pacific plate subduction was initiated in the Late Triassic to Early Jurassic.

The late Paleozoic to Mesozoic evolution of the eastern margin of the Central Asian Orogenic Belt in China

“…Because this has traditionally been related to Pacific-plate subduction, it is commonly excluded from the CAOB. However, recent work has indicated that many events here are coeval with late-stage activity in the CAOB (Zhou et al, 2014), and so their histories are closely aligned.…”

“…For the mafic rocks, a gabbro from Guanmen recorded an age of 216 ± 4 Ma and a basalt from Dadai (Fig. 4) an age of 167 ± 1 Ma (Zhou et al, 2014), thus establishing a similar range in ages for the igneous components. Detrital zircons within the clastic sedimentary matrix show a range in age from 2530 to 135 Ma (Zhou et al, 2014), indicating deposition in the Early Cretaceous, but with an Archean component similar to zircon ages reported widely from the North China Craton (e.g.…”

“…Wilde et al, 2005;Grant et al, 2009). Undeformed Cretaceous granites with an age of 125 Ma Zhou et al, 2014) intruded the Raohe Complex after its accretion.…”

Reconstruction of northeast Asian deformation integrated with western Pacific plate subduction since 200 Ma

“…1; Table 1) were represented by the accretion of the Nadanhada and Taukha terranes along the Sikhote-Alin belt in north-eastern China and the far eastern part of Russia (Zhou et al, 2014;Kemkin and Taketani, 2008;Malinovsky et al, 2008), as well as the South Kitakami-Kurosegawa block along the Sanbagawa and North Shimanto accretional zones in Shikoku. These Cretaceous accretional events were also represented by the south-eastern margin of Honshu and Hokkaido (Barnes, 2003) and a parallel Kyoke granite belt that was generated in the arc and that extended to the southern margin of South Korea and Sikhote-Alin in Russia (Taira, 2001).…”

“…These accretional complexes are assumed to have been continuous along the northeast Asian continental margin, but the Shimanto belt was discontinuous between western Japan and Hokkaido because of the deformation of the island arc. Zhou et al (2014) suggested that the Raohe complex in the Sikhote-Alin belt finally accreted to northeast Asia between 137 and 128 Ma. The Sanbagawa belt was divided into two sub-belts by Isozaki et al (2010b).…”