scholarly journals Sr, C, O Isotope Composition in Kimberlites of the North-russian Province (USSR)

2019 ◽  
Keyword(s):  
Isotope Composition ◽  
The North ◽  
O Isotope

Correlated Millennial-Scale Changes in Surface Hydrography and Terrigenous Sediment Yield Inferred from Last-Glacial Marine Deposits off Northeastern Brazil

1998 ◽  
Vol 50 (2) ◽  
pp. 157-166 ◽  
Author(s):  
Helge W. Arz ◽  
Jürgen Pätzold ◽  
Gerold Wefer
Keyword(s):  
North Atlantic ◽  
Isotope Composition ◽  
Sediment Cores ◽  
Ice Cores ◽  
Northeastern Brazil ◽  
Salt Flux ◽  
Terrigenous Sediment ◽  
The North ◽  
North Brazil ◽  
The North Atlantic

The stable isotope composition of planktonic foraminifera correlates with evidence for pulses of terrigenous sediment in a sediment core from the upper continental slope off northeastern Brazil. Stable oxygen isotope records of the planktonic foraminiferal species Globigerinoides sacculiferand Globigerinoides ruber(pink) reveal sub-Milankovitch changes in sea-surface hydrography during the last 85,000 yr. Warming of the surface water coincided with terrigenous sedimentation pulses that are inferred from high XRF intensities of Ti and Fe, and which suggest humid conditions in northeast Brazil. These tropical signals correlate with climatic oscillations recorded in Greenland ice cores (Dansgaard-Oeschger cycles) and in sediment cores from the North Atlantic (Heinrich events). Trade winds may have caused changes in the North Brazil Current that altered heat and salt flux into the North Atlantic, thus affecting the growth and decay of the large glacial ice sheets.

scholarly journals Iron and Carbon Isotope Constraints on the Formation Pathway of Iron-Rich Carbonates within the Dagushan Iron Formation, North China Craton

Minerals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 94
Author(s):  
Xiaoxue Tong ◽  
Kaarel Mänd ◽  
Yuhao Li ◽  
Lianchang Zhang ◽  
Zidong Peng ◽  
...  
Keyword(s):  
Iron Reduction ◽  
Isotope Composition ◽  
Iron Formation ◽  
Banded Iron Formations ◽  
Organic C ◽  
Formation Pathway ◽  
Wide Range ◽  
Dissimilatory Iron Reduction ◽  
O Isotope ◽  
Iron Formations

Banded iron formations (BIFs) are enigmatic chemical sedimentary rocks that chronicle the geochemical and microbial cycling of iron and carbon in the Precambrian. However, the formation pathways of Fe carbonate, namely siderite, remain disputed. Here, we provide photomicrographs, Fe, C and O isotope of siderite, and organic C isotope of the whole rock from the ~2.52 Ga Dagushan BIF in the Anshan area, China, to discuss the origin of siderite. There are small magnetite grains that occur as inclusions within siderite, suggesting a diagenetic origin of the siderite. Moreover, the siderites have a wide range of iron isotope compositions (δ56FeSd) from −0.180‰ to +0.463‰, and a relatively negative C isotope composition (δ13CSd = −6.20‰ to −1.57‰). These results are compatible with the reduction of an Fe(III)-oxyhydroxide precursor to dissolved Fe(II) through microbial dissimilatory iron reduction (DIR) during early diagenesis. Partial reduction of the precursor and possible mixing with seawater Fe(II) could explain the presence of siderite with negative δ56Fe, while sustained reaction of residual Fe(III)-oxyhydroxide could have produced siderite with positive δ56Fe values. Bicarbonate derived from both DIR and seawater may have provided a C source for siderite formation. Our results suggest that microbial respiration played an important role in the formation of siderite in the late Archean Dagushan BIF.

Zircon U-Pb dating and Hf-O isotope characteristics of Changchengian alkaline rocks from the Yanliao Rift in the North China Craton

2021 ◽  
Vol 37 (1) ◽  
pp. 231-252
Author(s):  
ZHANG Jian ◽  
◽  
LI HuaiKun ◽  
TIAN Hui ◽  
LIU Huan ◽  
...  
Keyword(s):  
North China Craton ◽  
North China ◽  
Alkaline Rocks ◽  
The North ◽  
O Isotope

scholarly journals Abnormal lithium isotope composition from the ancient lithospheric mantle beneath the North China Craton

2014 ◽  
Vol 4 (1) ◽  
Author(s):  
Yan-Jie Tang ◽  
Hong-Fu Zhang ◽  
Etienne Deloule ◽  
Ben-Xun Su ◽  
Ji-Feng Ying ◽  
...  
Keyword(s):  
North China Craton ◽  
Lithospheric Mantle ◽  
North China ◽  
Isotope Composition ◽  
Lithium Isotope ◽  
The North

Jilin Zircon – A New Natural Reference Material for Microbeam U-Pb Geochronology and Hf-O Isotopic Analysis

2021 ◽  
Author(s):  
Tao Luo ◽  
Qiuli Li ◽  
Xiaoxiao Ling ◽  
Yang Li ◽  
Chuan Yang ◽  
...  
Keyword(s):  
Reference Material ◽  
Isotope Composition ◽  
Isotopic Analysis ◽  
The Matrix ◽  
O Isotope

Zircon U-Pb geochronology and Hf-O isotope composition can provide important information on geological events. The matrix-matched reference material is routinely used to yield accurate and precise zircon U-Pb ages and...

scholarly journals A 45-year sub-annual reconstruction of seawater temperature in the Bay of Brest, France, using the shell oxygen isotope composition of the bivalve Glycymeris glycymeris

The Holocene ◽  
2019 ◽  
Vol 30 (1) ◽  
pp. 3-12 ◽  
Author(s):  
Amy M Featherstone ◽  
Paul G Butler ◽  
Bernd R Schöne ◽  
Melita Peharda ◽  
Julien Thébault
Keyword(s):  
North Atlantic ◽  
Isotope Composition ◽  
Seawater Temperature ◽  
Significant Negative Correlation ◽  
East Atlantic ◽  
The North ◽  
North Atlantic Subpolar Gyre ◽  
Climate Systems ◽  
Bay Of Brest ◽  
Insight Into

A reconstruction of sea surface temperature (SST) spanning 45 years (1966–2011) was developed from δ18O obtained from the aragonitic shells of Glycymeris glycymeris, collected from the Bay of Brest, France. Bivalve sampling was undertaken monthly between 2014 and 2015 using a dredge. In total, 401 live specimens and 243 articulated paired valves from dead specimens were collected, of which 24 individuals were used to reconstruct SST. Temperatures determined using the palaeotemperature equation of Royer et al. compared well with observed SST during the growing season between 1998 and 2010 (Pearson’s correlation: p = 0.002, r = 0.760). Furthermore, a significant negative correlation was found between the reconstructed SST and the North Atlantic Subpolar Gyre (SPG) index ( p = 0.001, r = −0.50), and a significant positive correlation was found with the East Atlantic Pattern (EAP) index when the reconstructed SST was lagged by 1 year ( p = 0.002, r = 0.46). This led to the conclusion that EAP and SPG are major influences on SSTs in the Bay of Brest. As the SPG controls air temperature in Northern Europe and the EAP controls water temperature in Southern Europe, this suggests that the Bay of Brest is an interaction area between these two climate systems. As such, this locality is interesting as the δ18O of the shells can be used as a proxy for both the SPG and EAP, and temperature reconstructions can provide a unique insight into how these climate systems interacted prior to the instrumental era.

scholarly journals Reservoirs and Radiocarbon: 14C Dating Problems in Mývatnssveit, Northern Iceland

Radiocarbon ◽  
2007 ◽  
Vol 49 (2) ◽  
pp. 947-961 ◽  
Author(s):  
Philippa L Ascough ◽  
Gordon T Cook ◽  
Mike J Church ◽  
Andrew J Dugmore ◽  
Thomas H McGovern ◽  
...  
Keyword(s):  
Isotope Composition ◽  
Bone Collagen ◽  
Archaeological Sites ◽  
North Coast ◽  
Spatial Gradient ◽  
Reservoir Effect ◽  
Terrestrial Mammal ◽  
Terrestrial Mammals ◽  
The North ◽  
Geothermal Activity

This paper examines 2 potential sources of the radiocarbon offset between human and terrestrial mammal (horse) bones recovered from Norse (∼AD 870–1000) pagan graves in Mývatnssveit, north Iceland. These are the marine and freshwater 14C reservoir effects that may be incorporated into human bones from dietary sources. The size of the marine 14C reservoir effect (MRE) during the Norse period was investigated by measurement of multiple paired samples (terrestrial mammal and marine mollusk shell) at 2 archaeological sites in Mývatnssveit and 1 site on the north Icelandic coast. These produced 3 new δR values for the north coast of Iceland, indicating a δR of 106 ± 10 14C yr at AD 868–985, and of 144 ± 28 14C yr at AD 1280–1400. These values are statistically comparable and give an overall weighted mean δR of 111 ± 10 14C yr.The freshwater reservoir effect was similarly quantified using freshwater fish bones from a site in Mývatnssveit. These show an offset of between 1285 and 1830 14C yr, where the fish are depleted in 14C relative to the terrestrial mammals. This is attributed to the input of geothermally derived CO2 into the groundwater and subsequently into Lake Mývatn. We conclude the following: i) some of the Norse inhabitants of Mývatnssveit incorporated non-terrestrial resources into their diet that may be identified from the stable isotope composition of their bone collagen; ii) the MRE off the north Icelandic coast during the Norse period fits a spatial gradient of wider North Atlantic MRE values with increasing values to the northwest; and iii) it is important to consider the effect that geothermal activity could have on the 14C activity of samples influenced by groundwater at Icelandic archaeological sites.

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