Hydrothermal Fluids and Cold Meteoric Waters along Tectonic-Controlled Open Spaces in Upper Cretaceous Carbonate Rocks, NE-Iraq: Scanning Data from In Situ U-Pb Geochronology and Microthermometry

The Upper Cretaceous carbonates along the Zagros thrust-fold belt “Harir-Safin anticlines” experienced extensive hot brine fluids that produced several phases of hydrothermal cements, including saddle dolomites. Detailed fluid inclusion microthermometry data show that saddle dolomites precipitated from hydrothermal (83–160 °C) and saline fluids (up to 25 eq. wt.% NaCl; i.e., seven times higher than the seawater salinity). The fluids interacted with brine/rocks during their circulation before invading the Upper Cretaceous carbonates. Two entrapment episodes (early and late) of FIs from the hydrothermal “HT” cements are recognized. The early episode is linked to fault-related fractures and was contemporaneous with the precipitation of the HT cements. The fluid inclusions leaked and were refilled during a later diagenetic phase. The late episode is consistent with low saline fluids (0.18 and 2.57 eq. wt.% NaCl) which had a meteoric origin. Utilizing the laser ablation U-Pb age dating method, two numerical absolute ages of ~70 Ma and 3.8 Ma are identified from calcrete levels in the Upper Cretaceous carbonates. These two ages obtained in the same level of calcrete indicate that this unit was twice exposed to subaerial conditions. The earlier exposure was associated with alveolar and other diagenetic features, such as dissolution, micritization, cementation, while the second calcrete level is associated with laminae, pisolitic, and microstromatolite features which formed during the regional uplifting of the area in Pliocene times. In conclusion, the hydrothermal-saddle dolomites were precipitated from high temperature saline fluids, while calcrete levels entrapped large monophase with very low salinity fluid inclusions, indicative for a low temperature precipitation from water with a meteoric origin.

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A Case Study Using 10Be-26Al Exposure Dating at the Xi’an AMS Center

Radiocarbon ◽

10.1017/rdc.2015.20 ◽

2016 ◽

Vol 58 (1) ◽

pp. 193-203 ◽

Cited By ~ 6

Author(s):

Li Zhang ◽

Zhenkun Wu ◽

Hong Chang ◽

Ming Li ◽

Guocheng Dong ◽

...

Keyword(s):

Sample Preparation ◽

Luminescence Dating ◽

Age Dating ◽

Published Data ◽

Exposure Dating ◽

Fluvial Terraces ◽

Exposure Age ◽

Close Relationship ◽

Dating Method

ABSTRACTExposure age dating using in situ10Be and 26Al is a very useful technique for dating fluvial terraces. This is especially true in semiarid regions where other methods suffer from a paucity of suitable dating materials. This article describes sample preparation procedures and analytical benchmarks established at the Xi’an Accelerator Mass Spectrometry (AMS) Center for the study of in situ10Be and 26Al. Four intercomparison samples were analyzed in the study, using an improved sample preparation method. The exposure age results are shown to be in good agreement with published data, and demonstrate the reliability of the dating method. This article also presents new 10Be and 26Al results from quartz samples collected from a series of fluvial terraces from Guanshan River, along the Qilian Shan, northeastern Tibetan Plateau. The ages of three fluvial terraces from the Jinfosi site are shown to be (56.4±5.3) ka for T3, (10.7±1.0) ka for T2, and (7.2±1.0) ka for T1. The dating results are consistent with published data from the same region (10Be, 14C, and optically stimulated luminescence dating methods). A comparison of high-resolution climate records with age constraints for the terrace formation shows a close relationship between terrace formation and climate change.

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Optimization of the in-situ U–Pb age dating method via LA-Quadrupole-ICP-MS with applications to the timing of U–Zr–Mo mineralization in the Poços de Caldas Alkaline Complex, SE Brazil

Journal of South American Earth Sciences ◽

10.1016/j.jsames.2015.04.007 ◽

2015 ◽

Vol 62 ◽

pp. 70-79 ◽

Cited By ~ 17

Author(s):

Lynthener Bianca Takenaka ◽

Cristiano Lana ◽

Ricardo Scholz ◽

Herminio Arias Nalini ◽

Adriana Tropia de Abreu

Keyword(s):

Age Dating ◽

Alkaline Complex ◽

Icp Ms ◽

Se Brazil ◽

Poços De Caldas ◽

Dating Method

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Sulfur bacteria promote dissolution of authigenic carbonates at marine methane seeps

The ISME Journal ◽

10.1038/s41396-021-00903-3 ◽

2021 ◽

Author(s):

Dalton J. Leprich ◽

Beverly E. Flood ◽

Peter R. Schroedl ◽

Elizabeth Ricci ◽

Jeffery J. Marlow ◽

...

Keyword(s):

Carbonate Rocks ◽

Sulfur Oxidation ◽

Methane Seeps ◽

Etch Pits ◽

Active Dissolution ◽

Authigenic Carbonates ◽

Sulfur Bacteria ◽

Sulfur Oxidizing ◽

Sulfur Oxidizing Bacteria

AbstractCarbonate rocks at marine methane seeps are commonly colonized by sulfur-oxidizing bacteria that co-occur with etch pits that suggest active dissolution. We show that sulfur-oxidizing bacteria are abundant on the surface of an exemplar seep carbonate collected from Del Mar East Methane Seep Field, USA. We then used bioreactors containing aragonite mineral coupons that simulate certain seep conditions to investigate plausible in situ rates of carbonate dissolution associated with sulfur-oxidizing bacteria. Bioreactors inoculated with a sulfur-oxidizing bacterial strain, Celeribacter baekdonensis LH4, growing on aragonite coupons induced dissolution rates in sulfidic, heterotrophic, and abiotic conditions of 1773.97 (±324.35), 152.81 (±123.27), and 272.99 (±249.96) μmol CaCO3 • cm−2 • yr−1, respectively. Steep gradients in pH were also measured within carbonate-attached biofilms using pH-sensitive fluorophores. Together, these results show that the production of acidic microenvironments in biofilms of sulfur-oxidizing bacteria are capable of dissolving carbonate rocks, even under well-buffered marine conditions. Our results support the hypothesis that authigenic carbonate rock dissolution driven by lithotrophic sulfur-oxidation constitutes a previously unknown carbon flux from the rock reservoir to the ocean and atmosphere.

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An example of in situ granite formation in the northern boundary of the Proterozoic Sergipano fold belt, NE Brazil: the Xingó Complex

Journal of South American Earth Sciences ◽

10.1016/0895-9811(95)00018-b ◽

1995 ◽

Vol 8 (3-4) ◽

pp. 341-354 ◽

Cited By ~ 7

Author(s):

I.P. Guimarães ◽

A.F. Da Silva Filho

Keyword(s):

Fold Belt ◽

Northern Boundary ◽

Granite Formation

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Late Mesozoic—Cenozoic clay mineral successions of southern Iran and their palaeoclimatic implications

Clay Minerals ◽

10.1180/0009855054020165 ◽

2005 ◽

Vol 40 (2) ◽

pp. 191-203 ◽

Cited By ~ 15

Author(s):

F. Khormali ◽

A. Abtahi ◽

H. R. Owliaie

Keyword(s):

Electron Microscopy ◽

Upper Cretaceous ◽

Sedimentary Rocks ◽

X Ray Diffraction ◽

Humid Climate ◽

X Ray ◽

Late Mesozoic ◽

Southern Iran ◽

Transmission Electron

AbstractClay minerals of calcareous sedimentary rocks of southern Iran, part of the old Tethys area, were investigated in order to determine their origin and distribution, and to reconstruct the palaeoclimate of the area. Chemical analysis, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and thin-section studies were performed on the 16 major sedimentary rocks of the Fars and Kuhgiluyeh Boyerahmad Provinces.Kaolinite, smectite, chlorite, illite, palygorskite and illite-smectite interstratified minerals were detected in the rocks studied. The results revealed that detrital input is possibly the main source of kaolinite, smectite, chlorite and illite, whilein situneoformation during the Tertiary shallow saline and alkaline environment could be the dominant cause of palygorskite occurrences in the sedimentary rocks.The presence of a large amount of kaolinite in the Lower Cretaceous sediments and the absence or rare occurrence of chlorite, smectite, palygorskite and illite are in accordance with the warm and humid climate of that period. Smaller amounts of kaolinite and the occurrence of smectite in Upper Cretaceous sediments indicate the gradual shift from warm and humid to more seasonal climate. The occurrence of palygorskite and smectite and the disappearance of kaolinite in the late Palaeocene sediments indicate the increase in aridity which has probably continued to the present time.

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Magnetic susceptibility and palaeomagnetic collection of rocks from central and western North Greenland

Rapport Grønlands Geologiske Undersøgelse ◽

10.34194/rapggu.v133.7983 ◽

1987 ◽

Vol 133 ◽

pp. 133-139

Author(s):

N Abrahamsen ◽

R Van der Voo

Keyword(s):

Magnetic Susceptibility ◽

Upper Cretaceous ◽

Crystalline Basement ◽

Mean Values ◽

Si Units ◽

Geometrical Mean ◽

Subsurface Mapping ◽

North Greenland

Some 1900 orientated palaeomagnetic samples were collected from 372 sites in central and western North Greenland in 1985 covering the complete rock sequence from the Precambrian crystalline basement to the Upper Cretaceous dolerite dykes. More than 1100 susceptibility measurements from 91 sites were measured in situ on as many rock units as possibie with susceptibilities above 10-4 SI units. The susceptibilities in the region span 4 orders of magnitude, but the geometrical mean values of major rock groups are well clustered and well defined suggesting that indirect subsurface mapping by aeromagnetic surveying may be a feasible tool for future investigations.

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Partitioning Effects during Terminal Carbon and Electron Flow in Sediments of a Low-Salinity Meltwater Pond near Bratina Island, McMurdo Ice Shelf, Antarctica

Applied and Environmental Microbiology ◽

10.1128/aem.65.12.5493-5499.1999 ◽

1999 ◽

Vol 65 (12) ◽

pp. 5493-5499 ◽

Cited By ~ 15

Author(s):

Douglas O. Mountfort ◽

Heinrich F. Kaspar ◽

Malcolm Downes ◽

Rodney A. Asher

Keyword(s):

Sulfate Reduction ◽

Methane Production ◽

Electron Flow ◽

Fold Increase ◽

Cyanobacterial Mats ◽

Ice Shelf ◽

Physiological Conditions ◽

Low Salinity ◽

Methane Production Rate

ABSTRACT A study of anaerobic sediments below cyanobacterial mats of a low-salinity meltwater pond called Orange Pond on the McMurdo Ice Shelf at temperatures simulating those in the summer season (<5°C) revealed that both sulfate reduction and methane production were important terminal anaerobic processes. Addition of [2-14C]acetate to sediment samples resulted in the passage of label mainly to CO2. Acetate addition (0 to 27 mM) had little effect on methanogenesis (a 1.1-fold increase), and while the rate of acetate dissimilation was greater than the rate of methane production (6.4 nmol cm−3 h−1compared to 2.5 to 6 nmol cm−3 h−1), the portion of methane production attributed to acetate cleavage was <2%. Substantial increases in the methane production rate were observed with H2 (2.4-fold), and H2 uptake was totally accounted for by methane production under physiological conditions. Formate also stimulated methane production (twofold), presumably through H2 release mediated through hydrogen lyase. Addition of sulfate up to 50-fold the natural levels in the sediment (interstitial concentration, ∼0.3 mM) did not substantially inhibit methanogenesis, but the process was inhibited by 50-fold chloride (36 mM). No net rate of methane oxidation was observed when sediments were incubated anaerobically, and denitrification rates were substantially lower than rates for sulfate reduction and methanogenesis. The results indicate that carbon flow from acetate is coupled mainly to sulfate reduction and that methane is largely generated from H2 and CO2 where chloride, but not sulfate, has a modulating role. Rates of methanogenesis at in situ temperatures were four- to fivefold less than maximal rates found at 20°C.

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