Iodine as a tracer of organic material: 129I results from gas hydrate systems and fore arc fluids

Fehn, Udo; Snyder, G. T.; Muramatsu, Yasuyuki

doi:10.1016/j.gexplo.2007.05.005

Cited by 63 publications

(23 citation statements)

References 56 publications

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“…Accordingly, deep-sourced pore fluids are, in most cases, devoid of SO 4 2À but strongly enriched in reduced components such as NH 4 + , I À and CH 4 (e.g., Aloisi et al, 2004;Wallmann et al, 2006a;Fehn et al, 2007;Gieskes and Mahn, 2007). Many of the pore fluids investigated here have lower salinities than normal seawater.…”

Section: Diagenetic Characterization Of Pore Fluidsmentioning

confidence: 77%

Lithium isotope geochemistry of marine pore waters – Insights from cold seep fluids

Scholz

Hensen

Lange

et al. 2010

Geochimica et Cosmochimica Acta

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Section: Diagenetic Characterization Of Pore Fluidsmentioning

confidence: 77%

Lithium isotope geochemistry of marine pore waters – Insights from cold seep fluids

Scholz

Hensen

Lange

et al. 2010

Geochimica et Cosmochimica Acta

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“…Background Values contain an average of 2.3, 0.8 and 2.7 ppm of iodine, respectively (Kebata-Pendias and Pendias, 1992;Fuge and Johnson, 1986), whereas iodine concentrations in soil samples from the Jamnagar area are up to 68.4 ppm. Organic matter is believed to be a major concentrator of iodine in petroliferous sedimentary basins (Birkle, 2006;Collins and Egleson, 1969;Fabryka-Martin et al, 1985;Kartsev, 1959;Mani et al, 2011a;Moran et al, 1995;Moran, 1996;Fehn et al, 2007;Muramastu and Wedepohl, 1998;Sheppard et al, 1995;Vinogradov, 1959;Whitehead, 1978). Soil iodine geochemistry has been related to subsequent drilling results, and iodine anomalies have been observed to exhibit a strong correlation with hydrocarbon accumulations (Leaver and Thomasson, 2002).…”

Section: Cumulative Frequencymentioning

confidence: 99%

Evaluation of Hydrocarbon Prospects Using Surface Geochemical Data With Constraints From Geological and Geophysical Observations: Saurashtra Basin, India

Mani

Patil

Kalpana

et al. 2011

Journal of Petroleum Geology

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The Saurashtra Basin in western India is considered to have significant hydrocarbon potential. However conventional exploration methods, particularly for Mesozoic prospects, have been hampered by the thick basalt cover. In this study, near-surface geochemical methods are used to investigate the generation of thermogenic gaseous hydrocarbons in the basin. Shallow soil samples were collected from favourable locations identified by integrated geophysical and geochemical studies. The compositional and isotopic signatures of adsorbed gaseous hydrocarbons (methane through pentane) together with soil iodine concentrations were used as surface indicators of petroleum micro-seepages. High concentrations of adsorbed thermogenic methane (C 1 = 518 ppb) and ethane plus higher hydrocarbons (ΣC 2+ =977 ppb) along with iodine concentrations up to 68.5 ppm were observed. Total organic and inorganic carbon (TOC and TIC) measurements, fluorescence and X-ray diffraction (XRD) studies showed that the nearsurface hydrocarbon occurrences were seepage related. Elevated hydrocarbon and iodine concentrations were coincident with dykes and lineaments in the study area, which probably served as conduits for the micro-seepage of hydrocarbons.

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“…Iodine is a biophilic element and is strongly enriched in organic matters (Elderfield and Truesdale 1980). Sediments on continental margins are enriched with iodine because of higher organic content and higher depositional rates than in open oceans (Martin et al 1993;Fehn et al 2007b). Thus, subducted marine sediments in the open ocean may not provide iodine to the forearc regions.…”

Section: Introductionmentioning

confidence: 99%

Groundwater, possibly originated from subducted sediments, in Joban and Hamadori areas, southern Tohoku, Japan

et al. 2014

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We studied the origin of deep groundwater in the Joban and Hamadori areas in southern Tohoku, Japan, based on δD, δ 18 O, 129I/I, 36 Cl/Cl, and 3 H concentrations. Deep groundwater was collected from the basement rocks (Cretaceous granite) and from the margin of the Joban sedimentary basin (latest Cretaceous to Quaternary sedimentary rocks deposited on the basement rocks). We sampled groundwater pumped from depths ranging from 350 to 1,600 m in these areas. A hypothetical end-member of deep groundwater was estimated from the relationship between δ 18 O and Cl concentrations, and our data reveal a much higher iodine concentration and lower Br and Cl concentrations than found in seawater. The iodine ages inferred from 129 I/I are quite uniform and are about 40 Ma and 36 Cl/Cl almost reached the secular equilibrium. The relationship between iodine and Cl can be explained by mixing a hypothetical end-member with meteoric water or seawater. Moreover, the I/Cl ratio increases linearly with increasing water temperature. The water temperature was high in Joban, with a maximum of 78°C at a depth of 1,100 m. The geothermal gradient in the Joban basin is 18°C km, and the temperature even at a depth of 3 km in the basin was not high enough to supply thermal water to the sampling sites. Thus, sedimentary rocks in the Joban basin are unlikely to be the source of iodine in the deep groundwater. Several active faults such as the Futaba Fault are developed in and around the studied areas. The Iwaki earthquake occurred 1 month after the 2011 Tohoku-oki earthquake, and normal-fault type surface ruptures formed and discharged hot groundwater in Joban. The deep groundwater we studied probably came up through the basement rocks from greater depths. There are no sedimentary rocks younger than Tertiary age beneath the pre-Cretaceous basement rocks, and the subducted sediments in the Japan Trench are a possible source of iodine in the groundwater. The Joban and Hamadori areas may be an ideal window to look into the water circulation in the forearc of the Tohoku subduction zone.

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Iodine as a tracer of organic material: 129I results from gas hydrate systems and fore arc fluids

Cited by 63 publications

References 56 publications

Lithium isotope geochemistry of marine pore waters – Insights from cold seep fluids

Lithium isotope geochemistry of marine pore waters – Insights from cold seep fluids

Evaluation of Hydrocarbon Prospects Using Surface Geochemical Data With Constraints From Geological and Geophysical Observations: Saurashtra Basin, India

Groundwater, possibly originated from subducted sediments, in Joban and Hamadori areas, southern Tohoku, Japan

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