Assessing chemostratigraphic and biostratigraphic …
The first phosphatic interval - or the lower phosphorite bed- age is bracketed between the basal cap carbonates dated at 635 ± 0.6 Ma (ash layer zircon U-Pb - Condon et al., 2005), and the U-Pb zircon age of 614 ± 7.6 Ma (Liu et al., 2009) obtained in tuff beds within the dolostone layer, situated below the karstic surface that separates the ...
Integrated Stratigraphy and Mineralogy of the Doushantuo Formation …
The Ediacaran–Cambrian Phosphogenic Episode is the Earth's first true phosphogenic event and resulted in worldwide phosphate deposits, which occurred during the processes of the Neoproterozoic Oxygenation Event. The Ediacaran Doushantuo Formation (ca. 635–551 Ma) of Weng'an area in central Guizhou, South China, contains two economic phosphorite beds (the …
Possible REE constraints on the depositional and
The Neoproterozoic Doushantuo Formation, South China, preserves a unique assemblage of what are probably the earliest metazoan fossils (sponges, cnidarians, and bilaterians) in the world that ...
Phosphorus flux during the Ediacaran: Rooted in continental …
In the Weng'an area, the Doushantuo Formation contains five units ... Samples were collected mainly from Unit 2 (the lower phosphorite layer) and Unit 4 (the upper phosphorite layer). Mineralogic observations were performed at the Institute of Geochemistry, Chinese Academy of Sciences (IGCAS), using a JEOL JSM–7800FX field emission scanning ...
Geochemistry and low-temperature thermochronology of
Based on these findings, the age of phosphorite mineralization in the upper phosphorite layer of the Meishucun Formation is approximately 539 Ma to 525 Ma, while the mineralization in the lower layer occurred slightly earlier, after the formation of the Doushantuo Formation and before 539 Ma.
Economic phosphorite from the Ediacaran Doushantuo …
Two complementary metallogenic processes resulted in the formation of high-grade phosphorite in the Doushantuo Formation. Synsedimentary winnowing and reworking of …
Rare earth element geochemistry of phosphatic rocks in …
Phosphatic rocks are widely distributed in Neoproterozoic Ediacaran Doushantuo Formation in Yangtze Gorges Area, South China. In this study, rare earth element geochemistry of eight phosphatic rock samples from the Hushan Section has been studied. All the samples display typical hat-shaped REE patterns, moderate negative Ce anomalies (Ce/Ce*=0.55 to …
Redox Environment and Its Significance for Phosphorus Formation …
The major and trace elements of the samples from the second member of Ediacaran Doushantuo Formation from the Wanjiagou section in the Zhangcunping area of western Hubei (South China) have been analyzed, so to constrain redox conditions of the Ediacaran ocean. ... The Lower Phosphorite Layer in the Zhangcunping area was deposited in …
Large-Scale Formation of Manganese, Phosphorus, and …
The Doushantuo phosphorite formed as the result of the concentration of phosphate near the near the redox interface through microbial ... All of the phosphatic layers developed in Doushantuo Formation, which occurred in both wings of Baiyan-Gaoping Anticline along the direction of south-north. Fig. 11. Geological map (a) and regional lithology ...
Economic phosphorite from the Ediacaran Doushantuo Formation…
At present, several phosphorite formation processes have been proposed, including the reworking of previous phosphate deposits (Föllmi, 1996;Ilyin, 1998;Yang et al., 2019; Zhang et al., 2019), in ...
Economic phosphorite from the Ediacaran Doushantuo Formation…
Lithofacies stacking patterns in the Doushantuo Formation record phosphorite deposition through two sea-level cycles. Resultant sequences are framed by a basal unconformity and two paleokarst surfaces at higher stratigraphic levels (Fig. 8, Fig. 9 A). In the Kaiyang region, the basal unconformity is developed directly on Cryogenian sedimentary ...
Origins of the Ediacaran Doushantuo High-Grade …
The phosphate ore layer is in the Sinian (Ediacaran) Doushantuo Formation. The Doushantuo Formation is distinctly similar to these formations, which were deposited between 635.2 ± 0.6 and 551.1 ± 0.7 Ma.
New Re–Os Geochronological Data from the Upper …
Three phosphorus-bearing layers are identified in the most shallow-water sediments, which occur in the bottom, middle, and top of the Doushantuo Formation. (35) The first phosphorus …
Mineralogical constraints on the paleoenvironments of the …
Isolated outcrops of the Doushantuo Formation are distributed across a large part of South China, recording sedimentation in the deep basin between the Cathaysian and Yangtze blocks in the southeast, and the broad shelves in the interior of the Yangtze craton in the north and west ().Details of the paleogeography and tectonic setting are still debated and are …
The Weng'an Biota (Doushantuo Formation): an
The base of the Dengying Formation can be dated to 551 Ma (Condon et al. 2005). In Weng'an, the Doushantuo Formation is composed of five units that have been described in detail by Xiao et al. (2014b) and Yin et al.. The Weng'an Biota occurs mainly in Unit 4, the Upper Phosphorite Member, but also in Unit 5.
A refined model for the mechanisms of Precambrian phosphorite formation
The depositional age of the Zhangcunping phosphorite beds is well constrained by: 1) a zircon U-Pb SHRIMP age of 614 ± 7.6 Ma was obtained from an ash layer on the top of lower phosphorite bed (Liu et al., 2008) and 2) a SIMS zircon U-Pb age of 609 ± 5 Ma (Zhou et al., 2017) and CA-ID-TIMS zircon U-Pb ages of 612.5 ± 0.9 Ma (Yang et al ...
Origins of the Ediacaran Doushantuo High-Grade …
early depositional stages of the Doushantuo Formation. Gray and black−gray, thin-bedded phosphorites (layer A) were deposited in relatively low topographic parts of the Weng'an, …
New Re–Os Geochronological Data from the Upper Doushantuo Formation …
A Pb–Pb age of 576 ± 14 Ma (MSWD = 0.4) from the upper phosphorite layers (Member III) of the Doushantuo Formation has been provided in the Weng'an section, located 750 km to the southwest of the Three Gorges region .
Dolostone-Barite-Phosphorite Sequence in the Basal Doushantuo Formation …
Dolostone-Barite-Phosphorite Sequence in the Basal Doushantuo Formation: Origin and Implications for Post-Marinoan Ocean Chemistry and Phosphogenesis ... B3 forms a centimeter-scale layer that laterally extends over the entire mining pit, whereas B2 is locally present as dense aggregates of unoriented tabular crystals between B1 and B3. δ34S ...
Study on the material source and enrichment …
Regionally, Guizhou Province is part of the Yangtze plate, which is mainly composed of phosphorite from the Ediacaran Doushantuo Formation and Cambrian Gezhongwu Formation. e large phosphorite ...
A new palaeo-weathering and leaching model for the formation …
The Kaiyang phosphate deposit is located in the margin of Shelf margin of the Yangtze Plate during the Ediacaran stage (Jiang, et al., 2011) (Fig. 1a).The phosphorite in this area is located mainly along the northern margin of the Qianzhong Craton and was formed during the Doushantuo stage of the Ediacaran (Fig. 1b).The phosphorus-bearing sequences are …
Study on the material source and enrichment mechanism of …
The lower ore layer is sandstone phosphorite, ... (1.83) > Doushantuo Formation phosphorite (1.18) > Niutitang Formation carbonaceous shale (1.08); this sequence reflects that the phosphorite from ...
Rare earth element and Sr–Nd isotope geochemistry of …
Phosphatic rocks are widely distributed in Neoproterozoic Ediacaran Doushantuo Formation in Yangtze Platform, South China. In this study, we examined samples from the Zhangcunping section in western Hubei Province with major element, rare earth element (REE) and Sr–Nd isotopic analyses on the phosphorites and the host dolostone rocks. We employed …
Dolostone-barite-phosphorite sequence in the basal …
Detailed petrographic observations of the basal Doushantuo Formation at Weng'an, South China reveal an evolutionary sequence from dolostone to barite and further to phosphorite. Three generations of barite are present at the transition between the cap dolostone and the …
Origin of the Ediacaran Weng'an and Kaiyang phosphorite …
Previous geochemical studies of the Doushantuo phosphorite deposits in South China have suggested that they formed under anoxic conditions. Nathan and Nielsen, 1980, Benmore, 1983 suggested that SO 4 2– isomorphically substituted PO 4 3– in carbonate–fluorapatite. Sulfur in marine sediments mainly originated from the reduction of …
Origins of the Ediacaran Doushantuo High-Grade Primary …
The Ediacaran Doushantuo phosphate deposit in Kaiyang, Guizhou Province, China, contains thick phosphate ores. Most of the ores are reconstituted phosphorite, and there have been few studies of the primary phosphorites, which has led to controversy regarding the origins and nature of mineralization of these phosphate-rich deposits. We identified high-grade …
The Weng'an Biota (Doushantuo Formation): an
In this Ediacaran fossil assemblage, organisms are phosphatized in cellular and even subcellular detail, providing a rare glimpse of soft-bodied and multicellular life at this time.
Origin of the Ediacaran Weng'an and Kaiyang phosphorite deposits …
However, several abiogenic phosphate granules have also been reported from the Doushantuo phosphorite deposits (Ye, 1989, Föllmi, 1996, Pufahl and Grimm, 2003, Chen et al., 2015).Observations made with transmitted light microscopy revealed that the phosphate granules of the lower layer were oval, with bright fibroid cements (Ye, 1989, Chen et al., 2015), and the …
Biostratigraphy of Doushantuo formation in Weng'an, …
from the phosphorite layers. They are the oldest evidence and unique to this area. Especially, the occurrence of small bilaterians ... We collected rock specimens from the 630 Ma Marinoan Glaciation through the black shale, dolomite and phosphorite of the Doushantuo Formation to the dolomite of the Dengying Formation in Weng'an, south China ...
Chemocline instability and isotope variations of the …
the Doushantuo Formation in this section consists of black shale, siltstone, very fine-grained sandstone and muddy/silty dolostone. Chert and phosphatic nodules and layers are present in this interval and they become more abundant towards the uppermost Doushantuo Formation. The Doushantuo-Dengying boundary in this