Stratigraphic architecture of the Neoproterozoic glacial rocks in the “Xiang-Qian-Gui” region of the central Yangtze Block, South China

Recently ,theinterestinglowlatitudeandlowaltitudeSnowballEarthhypothesis[1,2 ] iswidelyreco gnized ,and greatlystimulatingthestudyoftheNeoproterozoicglaciations ,whichmaybecloselyre latedtothewell knownEarlyCambrianbio radiationevent.By 1980 ,theNeoproterozoicglaciationinSouthChinaisbelievedtobedividedintotwoglaciationsandoneinterglaciation[3～ 5] ,namely ,theearlyChang’anGlaciation ,lateNantuoGlaciationandFu luInterglaciation .However ,thereweredifferentwaysofcorrelation ,themostobvious…     

Discussion on the Neoproterozoic glaciations in the South China Block and their related paleolatitudes

The Kaigas, Sturtian, Marinoan, and Gaskiers glaciations are widely recognized in Neoproterozoic. However, in the South China Block only the Jiangkou （Sturtian） and Nantuo （Marinoan） are symbolized by sedimentary records. The Kaigas, recorded by isotopic and chemical proxies, exhibited likely the nature of cold paleoclimate with local mountain glaciation. The correlation of the Doushantuo Formation with the Gaskiers is indicated by the carbon isotope excursion and the dated age from the interval, however the South China Block was then under non-glacial weather. With no paleomagnetic data, the position of the South China Block during the Sturtian glaciation cannot be determined. The paleolatitudes of the South China Block during the Kaigas and Nantuo glaciations are intermediate, even though the Nantuo was once rendered erratically deduced equatorial. In fact, the paleolatitudes of the South China Block during the Neoproterozoic glaciations are all likely at about 30°-40°.     

Phosphatized biotas from the Neoproterozoic Doushantuo Formation on the Yangtze Platform

The Doushantuo Formation in South China was deposited after the Nantuo glaciation but before the evolution of complex Ediacaran metazoans. It contains multiple taphonomic windows, in its cherts, carbonaceous shales, and phosphorites, onto the late Neoproterozoic biosphere. The phosphatic window is unusually clear; Doushantuo phosphorites at Weng'an (Guizhou Province) are known to exquisitely preserve a multitude of single-celled eukaryotes, multicellular algae, and microscopic animals. Our recent survey reveals that, in addition to the now famous Weng'an locality, Doushantuo phosphorites at Baokang (Hubei), Chadian (Shaanxi), and Shangrao (Jiangxi) also contain diverse eukaryotes preserved at the cellular level. All these phosphorites were deposited in shallow-water environments, typically above fair weather wave base and close to ancient islands. Along with Doushantuo cherts and shales, these phosphorites give us a clearer and more complete picture of late Neoproterozoic biological evolution: there is a remarkable diversification of multicellular eukaryotes shortly after several Neoproterozoic glaciation events.     

Petrogenesis of the Neoproterozoic bimodal volcanic rocks along the western margin of the Yangtze Block： New constraints from Hf isotopes and Fe/Mn ratios

High-precision major element and Hf isotope data are reported for the Neoproterozoic Suxiong volcanic rocks along the western margin of the Yangtze Block. These volcanic rocks have variable εHf（T） values and Fe/Mn ratios. The relatively primitive basalts have high Fe/Mn ratios and high Hf-Nd isotopic compositions, indicating that they were generated by partial melting of garnet clinopyroxene in mantle plume at high pressure. Thus, the Suxiong basalts are genetically related to the proposed Neoproterozoic superplume. On the contrary, a few differentiated basalts have low Fe/Mn ratios and low Hf-Nd isotopic compositions. They are likely to experience assimilation-fractional crystallization process. The Suxiong rhyolites have consistent Hf and Nd model ages of 1.3-1.4 Ga. They are likely generated by shallow dehydration melting of pre-existing young arc igneous rocks associated with the basaltic underplating/intrusion in a continental rift.     

西藏念青唐古拉地区铅锌银矿床成矿系列及找矿前景

在西藏念青唐古拉地区区域地质背景的综合研究基础上,通过对区内已知矿床、矿化(点)的分析,应用矿床成矿系列理论,将念青唐古拉成矿带主要矿床、矿化(点)划分为2个成矿系列,即海西中期海底喷流-沉积铜-铅-锌-重晶石-石膏矿床成矿系列、与燕山晚期中酸性侵入岩浆活动有关的钨-钼-铜-铅-锌-银矿床成矿系列.提出了区内矿床的找矿...     

Methane seeps, methane hydrate destabilization, and the late Neoproterozoic postglacial cap carbonates

Natural gas (methane) hydrates, the crystalline solids composed mainly of methane and water, are present in marine sediments of the continental margins and polar permafrost under a delicate balance of temperature (< 7℃) and hydrostatic pressure (> 50×10…