Meso-Neoproterozoic sedimentary evolution of the southern margin of the North China Craton: Evidence from the Huanglianduo and Dongjia formations in the western Henan

The Meso-Neoproterozoic sequences (the Ruyang, Luoyu, Huanglianduo, Dongjia, Luoquan and Dongpo groups/fonnations) deposited in the Mianchi-Queshan area after the Xiong' er volcanic-sedimentary succession within the southern margin of the North China Craton ( NCC) recorded the tectono-sedimentary histories of this region. Based on the new age constrains from detrital and magmatic zircon, the Ruyang and Luoyu groups belong to the Early Mesoproterozoic, i.e. , the Changcheng Period ( 1750 ~ 16()()Ma). As the Luoyu Group was thought to be deposited in the I.ate Mesoproterozoic to Neoproterozoic previously, it is necessary to study the Meso-Neoproterozoic sedimentary and tectonic evolution in the southern margin of NCC. The Huanglianduo Formation was deposited in a river estuary in the early stage. Following a transgression from the south to the north, feldspar-quartz sandstones and politic siltstones in a supratidal zone deposited in the Xiatang area, and dolomicrites in a intertidal zone occurred in the Yexian area. Siliceous banded dolomites and dolomicrites in a subtidal zone developed in the upper unit within the Xiatang and Yexian areas. The overlying Dongjia Formation consists of sediments in a coastal environment in the bottom unit. Fine-grained conglomerates and feldspar-quartz sandstones developed first in the Xiatang and Yexian areas. Then, feldspar-quartz sandstones and politic siltstones in the tidal flat facies, and the calcareous argillites of the restricted platform occurred in the upper unit of the Dongjia Fonnation. Therefore,the Huanglianduo Formation include the river estuary and tidal flat environments in the Xiatang area and tidal flat facies in the Yexian area, respectively. The Dongjia Formation was deposited in the littoral and tidal flat facies within a restricted marine basin as a whole. Comparing with the underlying sediments developed in the fluvial-coastal-tide flat facies ( Ruyang (/roup) and littoral to tidal flat facies (Luoyu Croup), both Huanglianduo and Dongjia formations show that restricted marine basin sequences occurred in the southern margin of NCC Evident depositional breaks and strong depocenter migration ( from Mianchi-Queshan and Songji area to Lushi-Luanchuan area) developed in the I.ate Mesoproterozoic. Detrital zircons were taken from the Huanglianduo, Dongjia and the Early Paleozoic Xinji formations within the NCC to track the changes in their provenances. The analyzed detrital zircon grains from the Huanglianduo and Dongjia fonnations display four dominant age peaks at ca. 1800Ma, 2250Ma, 2350Ma and 2650Ma, respectively, which suggest that their provenances were derived from the NCC. However, four major age peaks at ca. 185()Ma, 22(X)Ma, 25(X)Ma and 27(X)Ma, and one minor peak at ca. 12(X)Ma arc found in detrital zircon ages of the Xinji Formation. In combination with the Mesoproterozoic (iuandaokou and Neoproterozoic Luanchuan sequences and the widely occurred detrital zircon ages from the I.ate Mesoproterozoic to Neoproterozoic, the Huanglianduo and Dongjia formations could be deoposited in the basin margin. It is likely that the changes in the sedimentary environments and sources of the Huanglianduo, Dongjia formations and the overlying depositions, accompanied with the migration of the depocenter of the sedimentary basin and the uplifts of the basement, are related to the tectonic evolution during the late Mesoproterozoic to Neoproterozoic.