Geochemical controls on a calcite precipitating spring

Jacobson, R.L.; Usdowski, E.

doi:10.1007/bf00403513

Cited by 97 publications

(50 citation statements)

References 5 publications

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“…Nevertheless, the fact that the majority of BIFs are not associated with volcanic rocks, gives more credit to the hypothesis of a sedimentary origin. Furthermore, the source of the chemical elements is still widely debated with two main hypotheses considered valid: (i) a continental origin from the alteration of a continental crust, (ii) a hydrothermal origin (mantle for iron) involving the deposition of Fe and Si following a mixing of hydrothermal fluids rich in iron and silica with surface water [27][28]. On the other hand, the huge precipitation of Fe 3+ requires significant amount of oxygen.…”

Section: Origin and Tectonic Frameworkmentioning

confidence: 99%

Origin and Tectonic Framework of the Ngovayang Iron Massifs, South Cameroon

François¹

2016

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Abstract:The Ngovayang massifs belong to the Paleoproterozoic Nyong unit complex located in the north western edge of the Congo Craton of southern Cameroon. It consists of granitoids and a banded series. The banded series presents the petrographic and geochemical characteristics of greenstone belts similar to those of Sao Francisco Craton in Brazil. Pervious works in this area involved geochemical (% Fe), mineralogical (hematite/magnetite) and geophysical characterization of the formation ores. The sedimentary and tectonic events related to the ore emplacement are poorly understood and has an effect on the exploitation of these ores in Cameroon. The objective of this work is to generate new petrographic and geochemical data of the Ngovayang massifs, and to determine the origin and emplacement process that favored the accumulation of these ironbearing ferruginous quartzites in the study area. Polished thin sections were produced and observed using a scanning electron microscope at the Centre for Microscopy and Microanalysis, University of Western Australia CMM-UWA. Geochemical analysis of major and trace elements were carried out using XRF and ICP/MS in OMAC laboratory of Ireland. The results showed that the iron formation of the Ngovayang area composed of ferruginous and banded ferruginous quartzites series. Quartz, hematite and aluminosilicates occur as the main minerals associated with the ferruginous quartzite series. Geochemically, these ferruginous facies are very rich in Fe and Si but poor in other elements. Platy and massive type of mineralization were common with the hematites and are indicative of either metasomatic (or hydrothermal) origin and lateritic through meteoric water circulation. Three phase mineralization were identified from microscopic study: early Syn-sedimentary phase linked to the sedimentation of BIFs, a secondary tectonics phase and a tertiary phase related to weathering. The Ngovayang iron formations are characteristic of the lake superior-type.

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Section: Origin and Tectonic Frameworkmentioning

confidence: 99%

Origin and Tectonic Framework of the Ngovayang Iron Massifs, South Cameroon

François¹

2016

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“…Elevated concentrations of dissolved CO 2 in groundwater entering surface-water drainage systems will result in accelerated rates of CO 2 degassing which can significantly affect stream water-chemistry (Jacobson and Usdowski, 1975). Degassing of CO 2 will take place at a rate determined by stream dimensions, turbulence and wind-speed, but will invariably be susceptible to modification through biogeochemical processes (Wilcock et al, 1999).…”

Section: Dissolved Co 2 In Chalk Streamsmentioning

confidence: 99%

Variability of dissolved CO<sub>2</sub> in the Pang and Lambourn Chalk rivers

Griffiths

Nutter

Binley³

et al. 2007

Hydrol. Earth Syst. Sci.

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This paper presents the results of a two-year field campaign to determine the spatial and temporal variability of groundwater interaction with surface waters in two Cretaceous Chalk catchments (the Pang and Lambourn) in the Upper Thames in Berkshire, UK, based on measurement of dissolved carbon dioxide (CO 2 ). Average stream water concentrations of dissolved CO 2 were up to 35 times the concentration at atmospheric equilibrium. Mean groundwater concentrations of 85 and 70 times the atmospheric equilibrium were determined from borehole water sampled in the Pang and Lambourn respectively. Diurnal and seasonal variation of in-stream concentration of dissolved CO 2 is not significant enough to mask the signal from groundwater inputs.

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“…The hydrological and hydro-chemical karst-linked conditions control both chemical and biological degassing processes whilst Pe02 variations account for calcium carbonate precipitation (Jacobson and Usdowski, 1975;Julii, 1983;Emeis et aI., 1987;Pentecost, 1992).…”

Section: Introductionmentioning

confidence: 99%

Ostracode-based aminostratigraphy and aminochronology of a tufa system in central Spain

Torres¹,

Ortíz²,

Morena³

et al. 2005

Quaternary International

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In the Priego area, central Spain, extensive tufa deposits are located in three small tributaries located at the head of the 1000 kmlong Tagus River. The deposits are originated after karst-origin running waters emerged from the confines of the canyons and expanded outward. Old tufa deposits of Priego are mainly present as terraced alluvial plain deposits where different autochthonous and allochthonous facies appear. Extraclastic deposits of quartzite and limestone clasts derived from Mesozoic rocks are interbedded with the tufa marking pulsatory high-flow periods. Using the geomorphologic analysis six terraced levels were differentiated and sampled for ostracode amino acid racemization analysis. D/L ratios of aspartic acid and glutamic acid were used for dating purposes. Cluster analysis defined six aminozones (AMI-AM7) which were dated as follows: AMI: 407 ± 12 ka oxygen isotope stages (OIS 11); AM2: 263 ± 14 ka (OIS 7e); AM3: 181 ± 17 ka (OIS 7a); AM4: 136± 13 ka (OIS 5-6); AM5: 108 ± 14 ka (OIS 5); AM7: 11 ± 4 ka (OIS 1), indicating that tufa deposition took place during warm periods. Models of riverine and riverinebarrage tufa accumulation indicate that their maximum build-up took place between the canyon mouth and the point of depletion of dissolved CO 2 , and this affected the elevation of the top of the deposits and their relative chronology.

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Geochemical controls on a calcite precipitating spring

Cited by 97 publications

References 5 publications

Origin and Tectonic Framework of the Ngovayang Iron Massifs, South Cameroon

Origin and Tectonic Framework of the Ngovayang Iron Massifs, South Cameroon

Variability of dissolved CO<sub>2</sub> in the Pang and Lambourn Chalk rivers

Ostracode-based aminostratigraphy and aminochronology of a tufa system in central Spain

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Geochemical controls on a calcite precipitating spring

Cited by 97 publications

References 5 publications

Origin and Tectonic Framework of the Ngovayang Iron Massifs, South Cameroon

Origin and Tectonic Framework of the Ngovayang Iron Massifs, South Cameroon

Variability of dissolved CO&lt;sub&gt;2&lt;/sub&gt; in the Pang and Lambourn Chalk rivers

Ostracode-based aminostratigraphy and aminochronology of a tufa system in central Spain

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Variability of dissolved CO<sub>2</sub> in the Pang and Lambourn Chalk rivers