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Sunnyvale, CA, United States

Koerner G.R.,GSI Inc
ASTM Special Technical Publication | Year: 2013

A practical method is described to determine the carbonate content of the bentonites used in geosynthetic clay liners (GCLs). The determination of the carbonate content of bentonite uses a reactor wherein hydrochloric acid (HCl) is mixed with the bentonite specimen in a closed vessel. After activation, the reaction creates carbon dioxide (CO2) pressure proportional to the calcium carbonate (CaCO3) content of the sample. It has been suggested that the calcium carbonate content might be related to long-term performance insofar as cation exchange is concerned. In addition to determining the CaCO3 content of the various bentonites, long-term permeability tests were conducted on the same GCL specimens to illustrate this possibility. Copyright © 2013 by ASTM International.

Gupta S.,Geological Survey of India | Fareeduddin,GSI Inc
Journal of the Geological Society of India | Year: 2013

Paragonite (NaAl2Si3AlO10(OH) 2), a dioctahedral sodium mica, occurs as a minor phase in the wall rock alteration assemblage of the Guddadarangavanahalli (G. R. Halli) gold deposit of Western Dharwar Craton, Karnataka. It occurs as colourless to pale yellowish grains and scaly aggregates in chlorite, ankerite and quartz rich matrix of the altered metabasalt. Its presence is noticed in the distal to near proximal wall rock alteration zone, mainly in the southern part of the G. R. Halli gold deposit. Presence of paragonite is identified by X-Ray Diffraction (XRD) and Electron Probe Micro-Analyzer (EPMA) studies. The Na2O content of the paragonite varies between 5.96 wt% and 7.8 wt% whereas K 2O ranges from 0.44-2.68 wt%. Al2O3 is measured between 37.73 wt% and 39.72 wt% whereas SiO2 varies from 45.06-47.19 wt%. The relative proportion of Na and K in paragonite varies between Na 96K4 and Na77K23. The occurrence of paragonite in the wall rock alteration halo of the G. R. Halli gold deposit is proposed as a result of hydrolysis of metamorphosed plagioclase feldspars during the interaction of the hydrothermal fluids and the wall rock. © 2013 Geological Society of India.

Gupta S.,Geological Survey of India | Jayananda M.,University of Delhi | Fareeduddin,GSI Inc
Geoscience Frontiers | Year: 2014

Tourmaline occurs as a minor but important mineral in the alteration zone of the Archean orogenic gold deposit of Guddadarangavanahalli (G.R.Halli) in the Chitradurga greenstone belt of the western Dharwar craton, southern India. It occurs in the distal alteration halo of the G.R.Halli gold deposit as (a) clusters of very fine grained aggregates which form a minor constituent in the matrix of the altered metabasalt (AMB tourmaline) and (b) in quartz-carbonate veins (vein tourmaline). The vein tourmaline, based upon the association of specifi c carbonate minerals, is further grouped as (i) albite-tourmaline-ankerite-quartz veins (vein-1 tourmaline) and (ii) albite-tourmaline-calcite-quartz veins (vein-2 tourmaline). Both the AMB tourmaline and the vein tourmalines (vein-1 and vein 2) belong to the alkali group and are classified under schorl-dravite series. Tourmalines occurring in the veins are zoned while the AMB tourmalines are unzoned. Mineral chemistry and discrimination diagrams reveal that cores and rims of the vein tourmalines are distinctly different. Core composition of the vein tourmalines is similar to the composition of the AMB tourmaline. The formation of the AMB tourmaline and cores of the vein tourmalines are proposed to be related to the regional D1 deformational event associated with the emplacement of the adjoining ca. 2.61 Ga Chitradurga granite whilst rims of the vein tourmalines vis-àvis gold mineralization is spatially linked to the juvenile magmatic accretion (2.56 e2.50 Ga) east of the studied area in the western part of the eastern Dharwar craton. © 2014 China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. All rights reserved.

Davidson A.N.,University of Texas at Austin | Davidson A.N.,GSI Inc | Chee-Sanford J.,University of Illinois at Urbana - Champaign | Lai H.Y.M.,University of Texas at Austin | And 3 more authors.
Water Research | Year: 2011

The objective of the current study was to isolate and characterize several bromate-reducing bacteria and to examine their potential for bioaugmentation to a drinking water treatment process. Fifteen bromate-reducing bacteria were isolated from three sources. According to 16S rRNA gene sequencing, the bromate-reducing bacteria are phylogenetically diverse, representing the Actinobacteria, Bacteroidetes, Firmicutes, and α-, β-, and γ- Proteobacteria. The broad diversity of bromate-reducing bacteria suggests the widespread capability for microbial bromate reduction. While the cometabolism of bromate via nitrate reductase and (per)chlorate reductase has been postulated, five of our bromate-reducing isolates were unable to reduce nitrate or perchlorate. This suggests that a bromate-specific reduction pathway might exist in some microorganisms. Bioaugmentation of activated carbon filters with eight of the bromate-reducing isolates did not significantly decrease start-up time or increase bromate removal as compared to control filters. To optimize bromate reduction in a biological drinking water treatment process, the predominant mechanism of bromate reduction (i.e., cometabolic or respiratory) needs to be assessed so that appropriate measures can be taken to improve bromate removal. © 2011 Elsevier Ltd.


GSI Inc | Date: 2016-03-02

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