Neoproterozoic subduction along the Ailaoshan zone, South China : geochronological and geochemical evidence from amphibolite

This study was supported by China Natural Science Foundation (41190073 and 41372198), National Basic Research Program of China (2014CB440901) and Natural Environment Research Council (grant NE/J021822/1).Lenses of amphibolites occur along the Ailaoshan suture zone at the southwestern margin of the Yangtze Block, South China. Petrological, geochemical and zircon U-Pb geochronological data indicate that they are divisible into two coeval groups. Group 1, represented by the Jinping amphibolite, has mg-number of 71-76 and (La/Yb)cn ratios of 7.2-7.7, and displays a geochemical affinity to island arc volcanic rocks. Group 2 amphibolites occur at Yuanyang and are characterized by high Nb contents (14.3-18.4 ppm), resembling Nb-enriched basalts. The epsilon(Nd)(t) values for Group 1 range from -3.45 to -2.04 and for Group 2 from +4.08 to +4.39. A representative sample for Group 1 yields a U-Pb zircon age of 803 7 Ma, whereas two samples for Group 2 give U-Pb zircon ages of 813 +/- 11 Ma and 814 +/- 12 Ma. Petrogenetic analysis suggests that Group 1 originated from an orthopyroxene-rich source and Group 2 from a mantle wedge modified by slab-derived melt. In combination with other geological observations, these amphibolites are inferred to constitute part of an early Neoproterozoic (similar to 815-800 Ma) arc-back-arc basin system. The Neoproterozoic amphibolites and related rocks along the Ailaoshan zone may be the southward extension of the Neoproterozoic supra-subduction zone that developed along the western margin of the Yangtze Block. (C) 2014 Elsevier B.V. All rights reserved.PostprintPeer reviewe

Complete mitochondrial genome sequence of Glyptothorax annandalei in the Yarlung Zangbo River, Tibet

Glyptothorax annandalei belongs to the family of Sisoridae, Glyptothorax. It is distributed in the Yarlung Zangbo River of southwestern China. In this study, we first published the complete mitochondrial genome sequence of Glyptothorax annandalei, which was 16,541 bp in length. This genome consists of two rRNA genes, 22 tRNA genes, 13 protein-coding genes (PCGs), and a putative control region. The overall base composition was for A(31.25%,) for T(25.67%), for C(27.66%), for G(15.42%). The PCGs start with a traditional ATG except for COX1 start with GTG, respectively, and end with stop codon TAA, TAG, or a single T base. All tRNA have the typical clover-leaf structure. The phylogenetic tree of the whole mitogenome sequence is constructed by maximum likelihood (ML) method and the phylogenetic relationship among the family Sisoridae is further analyzed. We expect to provide the theoretical basis for the further study of the phylogenetic relationship, taxonomic status, conservation and management of genetic resources of Sisoridae catfishes

The first complete mitochondrial genome of macroparasite Crassicauda magna (Nematoda: Spirurida) from Neophocoena sunameri in ningbo, China

Members of the genus Crassicauda (Nematoda: Spirurida) are macroparasites infect the body tissues of whales and dolphins. However, limited information is available on morphological descriptions and phylogenetic studies of the worms. In present study, we report the first complete mitochondrial genome of Crassicauda magna from Neophocoena sunameri in Ningbo, Zhejiang Provence, China. The mitogenome has 13,605 base pairs (74.97% A + T content) and is made up of a total of 36 genes (12 protein-coding, 22 transfer RNAs, and 2 ribosomal RNAs). This study will provide useful molecular information for addressing taxonomic and evolutionary issues in Crassicauda sp.

Complete mitochondrial genome sequence of Pareuchiloglanis kamengensis in the Yarlung Zangbo River, Tibet

Pareuchiloglanis kamengensis belongs to the family of Sisoridae, Pareuchiloglanis. It is distributed in the Yarlung Zangbo River, the Irrawaddy River, the Nujiang River, and the Lancang River in southwestern China. In this study, we first published the complete mitochondrial genome sequence of Pareuchiloglanis kamengensis, which was 16,589 bp in length. This genome consists of 13 protein-coding genes (PCGs), 22 tRNA genes, two rRNA genes, and a non-coding A + T-rich region. The PCGs start with a traditional ATG except for COX1 and NAD3, which start with GTG and ATA instead, respectively, and end with stop codon TAA, TAG, TA, or a single T base. All tRNA have the typical clover-leaf structure. The phylogenetic tree of the whole mitogenome sequence is constructed by using neighbor-joining (NJ) method and the phylogenetic relationship among the family Sisoridae is further analyzed. We except to provide the theoretical basis for the further study of the phylogenetic relationship, taxonomic status, and conservation and management of genetic resources of Sisoridae catfishes

Discovery and basic characteristics of high-quality source rocks found in the Yuertusi Formation of the Cambrian in Tarim Basin, China

The Upper Paleozoic strata of the Tarim Basin have abundant resources of marine oil and gas. In the Tahe area, Halahatang area, and Tazhong area of the basin, many large-scale oilfields have been found. These oilfields have a confirmed oil and gas reserves worth more than 2.5 billion tons and have completed the annual output of more than 14 million tons of marine oil and gas equivalent. The belief that the only main hydrocarbon source rocks are of the Cambrian or Ordovician is still controversial. Chemists have made significant progress and have effectively lead the oil and gas exploration in Tarim Basin. Due to the complexity of the basin and the limitation of samples, the research work, and fine contrast is restricted. In this article, we investigated the Cambrian strata outcrop of Tarim Basin in detail. By analyzing a lot of outcrops, high-quality hydrocarbon source rocks of Yuertusi Formation have been found in more than 10 outcrop points in Aksu region. The source rocks' lithology is black shale with total organic carbon (TOC) content that ranges between 2% and 16%. Total organic carbon (TOC) of the black shale layer could be as much as 4%–16%, especially in the outcrops of the Yutixi and Shiairike. This by far is the best marine hydrocarbon source rock that was found in China. The source rocks were distributed consistently in the Aksu region, the thickness of which is about 10–15 m. It was formed in a sedimentary environment of a middle gentle slope to a low gentle slope. Organic matter enrichment is controlled by the upwelling currents. The thick strata of dolostone that developed in the Xiaoerblak Formation are considered to be good reservoirs of the beach and microbial reef in the upper strata of Yuertusi Formation. No hydrocarbon source rocks have been found in the outcrop of Xiaoerblak Formation. The thick strata of gyprock and mudstone development are a set of satisfactory cap layer in the Lower Cambrian. This hydrocarbon accumulation combination has great exploration potential

Isotopic differences and paleoenvironmental significance of nitrogen contained in bulk sedimentary rocks, decarbonated aliquots and kerogen extracts

The stable nitrogen isotopic composition (δ15N) of sedimentary rocks is an important tool for reconstructing the paleo-oceanic nitrogen cycle and has been widely used in palaeoenvironmental studies of the Precambrian and Phanerozoic. Currently, the commonly used parameters are the isotopic compositions of decarbonated samples (δ15NDCN) and kerogen extracts (δ15Nkerogen). However, some studies have shown that there are differences between these two proxies. In addition, differences were found between δ15NDCN and the nitrogen isotopic compositions of untreated samples (δ15Nbulk). In order to explain these phenomena, we selected sedimentary rock samples from different time periods in the Phanerozoic and analyzed nitrogen isotopes after all three treatments (bulk rock, decarbonated rock, and kerogen extracts). We find that (1) δ15Nbulk is greater than δ15NDCN in most samples by 0.6‰ on average, indicating that acid-soluble organic N with higher δ15N values was lost preferentially during decarbonization; (2) δ15NDCN is greater than δ15Nkerogen mainly in anoxic environments, which may be linked to ammonium accumulation in pore fluids or in the water column during deposition and/or diagenesis. For example, the anaerobic ammonia oxidation process and partial assimilation preferentially consume 14NH4+ and enrich 15NH4+ in seawater. Therefore, NH4+ fixed by clay minerals may have a higher δ15N than organic nitrogen; (3) δ15Nkerogen greater than δ15NDCN was observed in a subset of samples and may reflect either preferential release of 14NH4+ from organic matter or biological production of isotopically light NH4+, followed by adsorption to clay minerals. In this case, the δ15N of residual organic nitrogen would be relatively high compared to the released NH4+. However, this scenario is only retained in samples that have not undergone significant post-depositional alteration, which tends to lower δ15Nkerogen and increase δ15NDCN. Differences between the three nitrogen parameters are in many cases small and would not alter overall paleoenvironmental interpretations; however, in some cases, they can be significant and carry additional information about diagenetic conditions that may be unlocked with additional studies on wider range of deposition environments