Unusual N-alkane distributions in extracts from marine carbonate rocks at high levels of maturity and overmaturity

2002 ◽  
Vol 21 (4) ◽  
pp. 322-333 ◽  
Author(s):  
Li Jinggui ◽  
R. Paul Philp ◽  
Cui Mingzhong
Keyword(s):  
Carbonate Rocks ◽  
Marine Carbonate ◽  
Marine Carbonate Rocks

scholarly journals The Remagnetization of Marine Carbonate Rocks of the Late Ordovician in Pingliang Section, Southwest Ordos (China)

2019 ◽  
Vol 93 (S3) ◽  
pp. 132-134
Author(s):  
Junhua LUO ◽  
Shuang DAI ◽  
Mark DEKKERS ◽  
Weiguo WANG ◽  
Xiaoke QIANG ◽  
...  
Keyword(s):  
Carbonate Rocks ◽  
Late Ordovician ◽  
Marine Carbonate ◽  
Marine Carbonate Rocks

The Shibantan Lagerstätte: insights into the Proterozoic–Phanerozoic transition

2020 ◽  
Vol 178 (1) ◽  
pp. jgs2020-135
Author(s):  
Shuhai Xiao ◽  
Zhe Chen ◽  
Ke Pang ◽  
Chuanming Zhou ◽  
Xunlai Yuan
Keyword(s):  
South China ◽  
Carbonate Rocks ◽  
Microbial Mats ◽  
Ecological Interactions ◽  
Benthic Organisms ◽  
Important Data ◽  
Ediacara Biota ◽  
Marine Carbonate ◽  
Fossil Assemblages ◽  
Marine Carbonate Rocks

The Shibantan Lagerstätte (551–543 Ma) in the Yangtse Gorges area in South China is one of the best-known examples of terminal Ediacaran fossil assemblages preserved in marine carbonate rocks. Taxonomically dominated by benthic organisms, the Shibantan Lagerstätte preserves various photoautotrophs, biomineralizing tubular fossils, Ediacara-type macrofossils (including rangeomorphs, arboreomorphs, erniettomorphs, palaeopascichnids, a possible dickinsoniomorph, the mobile bilaterian Yilingia and soft-bodied tubular fossils), abundant ichnofossils and a number of problematic and dubious fossils. Shibantan fossils provide intriguing insights into ecological interactions among mobile bilaterians, sessile benthic Ediacara-type organisms and microbial mats, thus offering important data to test various hypotheses accounting for the decline of the Ediacara biota and the concurrent expansion of bilaterian bioturbation and mobility across the Proterozoic–Phanerozoic transition.

scholarly journals Stable Isotope (S, Mg, B) Constraints on the Origin of the Early Precambrian Zhaoanzhuang Serpentine-Magnetite Deposit, Southern North China Craton

Minerals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 377 ◽  
Author(s):  
Jie Meng ◽  
Houmin Li ◽  
Yanhe Li ◽  
Zhaochong Zhang ◽  
Lixing Li ◽  
...  
Keyword(s):  
North China Craton ◽  
Carbonate Rocks ◽  
North China ◽  
Mean Value ◽  
Coarse Grained ◽  
Sulfur Source ◽  
Marine Carbonate ◽  
Isotopic Analyses ◽  
Wide Range ◽  
Marine Carbonate Rocks

The origin of the Zhaoanzhuang serpentine-magnetite deposit in the southern North China Craton (NCC) is highly disputed, with some investigators having proposed an ultramafic origin, whereas others favor a chemical sedimentary origin. These discrepancies are largely due to the difficulty in determining the protolithic characteristics of the highly metamorphosed rocks. Sulfur, magnesium, and boron isotope geochemistry combined with detailed petrography was carried out in this study to constrain the original composition of the Zhaoanzhuang iron orebodies. Anhydrite is present as coarse crystals intergrown with magnetite, indicating that the anhydrite formed simultaneously with the magnetite during metamorphism rather than as a product of later hydrothermal alteration. The anhydrite has a narrow range of positive δ34S values from +19.8 to +22.5‰ with a mean value of +21.1‰. These values are significantly higher than that of typical magmatic sulfur (δ34S = 0 ± 5‰) and deviate away from primary igneous anhydrite towards mantle-sulfur isotopic values, but they are similar to those of marine evaporitic anhydrite and gypsum (~+21‰). The sulfur isotopic compositions of several samples show obvious signs of mass-independent sulfur fractionation (Δ33S = −0.47‰ to +0.90‰), suggesting that they were influenced by an external sulfur source through a photochemical reaction at low oxygen concentrations, which is consistent with the Neoarchean-Paleoproterozoic atmosphere. Coarse-grained tourmaline from the tourmaline-rich interlayers of the orebodies occurs closely with Mg-rich minerals such as phlogopite, talc, and diopside, indicating that it has a metamorphic origin. The δ11B values of the tourmaline range from −0.2‰ to +3.6‰ with a mean value of +2.0‰, which is much positive relative to that of magmatic tourmaline but is consistent with that of carbonate-derived tourmaline. The magnesium isotopic analyses of the serpentine–magnetite ores and the magnesium-rich wall rocks revealed a wide range of very negative δ26Mg values from −1.20‰ to −0.34‰ with an average value of −0.80‰. The value is higher than that of ultramafic rocks (δ26Mg = −0.25‰) and exhibits minor Mg isotopic fractionation. However, these values are consistent with those of marine carbonate rocks, which have lower δ26Mg values and larger Mg isotopic variations (δ26Mg = −0.45‰ to −4.5‰). Collectively, the S–Mg–B isotopic characteristics of the Zhaoanzhuang iron orebodies clearly indicate a chemical sedimentary origin. The protoliths of these orebodies most likely reflect a series of Fe–Si–Mg-rich marine carbonate rocks with a considerable evaporite component, indicating a carbonate-rich superior-type banded iron formation precipitated in an evaporitic shallow marine sedimentary environment.

scholarly journals Type division and controlling factor analysis of 3rd-order sequences in marine carbonate rocks

2014 ◽  
Vol 5 (2) ◽  
pp. 289-298
Author(s):  
Yunbo Zhang ◽  
Zongju Zhao ◽  
Genhou Wang ◽  
Zaixing Jiang ◽  
Mingjian Wang ◽  
...  
Keyword(s):  
Factor Analysis ◽  
Carbonate Rocks ◽  
Controlling Factor ◽  
Marine Carbonate ◽  
Marine Carbonate Rocks
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