Tresa Thomas | Pondicherry Central University, India (original) (raw)

Papers by Tresa Thomas

Journal of Earth System Science, 2021

Uranium mineralization occurs adjacent to the unconformity between Paleoproterozoic granite and M... more Uranium mineralization occurs adjacent to the unconformity between Paleoproterozoic granite and Meso- to Neoproterozoic cover sediments in Chitrial prospect of Cuddapah Basin in Indian shield. Hydrothermal activity in the granite is evident by the presence of hydrothermal veins and associated wallrock alteration in the unconformity zone (0–5 m below unconformity), shallow zone (5–100 m), and deep zone (100–120 m). Hydrothermal alteration of granite has produced chlorite in all depth, epidote in the deep zone, muscovite commonly in the shallow zone and illite predominantly in the unconformity zone. Pitchblende and coffinite are associated with sulphides and carbonaceous matter filling micro fractures and occurring along grain boundaries in the granite. Fluid inclusion study of quartz from hydrothermal veins reveals the presence of primary aqueous inclusions (biphase, monophase, polyphase) with a wide range of salinity from 0.2 to >23.2 wt.% (low–high). The fluid composition indica...

Journal of Asian Earth Sciences, 2014

ABSTRACT Unconformity related uranium mineralisation occurs in Banganapalle Formation of Palnad S... more ABSTRACT Unconformity related uranium mineralisation occurs in Banganapalle Formation of Palnad Sub-basin, Cuddapah Basin. Several evidences of hydrothermal activity exist in both basement granite and the cover sediments in Koppunuru and Rallavagu Tanda (R.V. Tanda) uranium prospects of Palnad Sub-basin. Profuse development of fracture filled veins consisting of epidote–quartz, chlorite–quartz and quartz is observed at various depths above and below unconformity. Fluid–rock interaction during the formation of these veins has resulted in the alteration of feldspars and mafic minerals of granite and arkosic quartzite into a mineral assemblage consisting of various proportion of illite, chlorite, muscovite and pyrite, with the intensity of alterations being highest near to the unconformity. Pyrite is often associated with illite dominant alteration zone. We infer that circulation of basinal brine through basement granite and cover sediments was responsible for mobilising uranium from granite and its precipitation at favourable locations in cover sediments. Increase in pH of ore fluid due to illitisation and chloritisation of wallrock together with availability of carbonaceous matter and pyrite as reductant have controlled the localisation of uranium mineralisation in Banganapalle Formation.

Journal of Applied Geochemistry, Vol. 16(4), pp. 361-380, Oct 1, 2014

Radioactive granitoids and cherty cataclasites are delineated in Thadisaoli–Khatgaon and Shahpur–... more Radioactive granitoids and cherty cataclasites are delineated in Thadisaoli–Khatgaon and Shahpur–Sujayatpur sectors in southeastern part of Nanded district, Maharashtra, which have recorded anomalous radioelemental contents (Granites: upto 1% U3O8 and 0.20% ThO2; Cherty cataclasites upto 0.11% U3O8 and <0.005% ThO2) and enrichment in trace element and rare metal and rare earth element concentration (Nb: upto 146ppm, Y: upto 226ppm, Zr: upto 559ppm and total REE: upto 2010ppm). The mineralised granitoids are affected by profuse pegmatitic/quartzo-feldspathic, quartz and epidote venations and mainly confined along the NE–SW and NNE–SSW faults/shear zones. Radioactive phases are represented by discrete uranium/thorium ore minerals (uraninite, -uranophane and thorite) and high content of resistates viz., apatite, zircon, allanite, sphene, cerianite, monazite and ilmenite.
Fluid inclusion studies of the mineralised and sheared granites, quartzo-feldspathic veins (QFVs) and quartz veins indicate the presence of 6 to 32µm size aqueous and carbonic inclusions of three principle types and represented by six phases viz., aqueous mono-, bi- and poly-phase, aqueous-carbonic, carbonic mono- and poly-phase. Aqueous biphase inclusions show wide range of salinity (0.71 to 19.99 wt.% eNaCl) and homogenisation temperatures (Th: 127.5–280.8ºC ) while aqueous-carbonic inclusions exhibit restricted salinity (5–8.4 wt.% eNaCl ) and Th (28.3–30.9ºC). The composition of these aqueous fluids varies from NaCl–KCl dominant in quartz veins and radioactive granite to MgCl2 dominant in sheared radioactive granite. Similarly, co-eval aqueous biphase and aqueous-carbonic inclusions have yielded 678–958 bar pressure and 201–233ºC temperature in quartz vein samples while higher values of 1120–1550 bar and 304–360ºC are indicated by sheared granite. The presence of more than one population without much change in fluid composition signifies their origin at different stages of deformation. Besides, mixing of a moderate temperature and low salinity fluid (meteoric/basinal brine) with a comparatively high temperature and hypersaline fluid (magmatic/evolved brine) might have also played important role in inclusion characteristics. Based on these fluid inclusion characteristics, it appears that multi-episodic hydrothermal activity under extensional tectonic regime in this fertile granitic province has led to precipitation of uranium along suitable structural aureoles from uraniferous hydrotherms.

Journal of Asian Earth Sciences, 2014

ABSTRACT Unconformity related uranium mineralisation occurs in Banganapalle Formation of Palnad S... more ABSTRACT Unconformity related uranium mineralisation occurs in Banganapalle Formation of Palnad Sub-basin, Cuddapah Basin. Several evidences of hydrothermal activity exist in both basement granite and the cover sediments in Koppunuru and Rallavagu Tanda (R.V. Tanda) uranium prospects of Palnad Sub-basin. Profuse development of fracture filled veins consisting of epidote–quartz, chlorite–quartz and quartz is observed at various depths above and below unconformity. Fluid–rock interaction during the formation of these veins has resulted in the alteration of feldspars and mafic minerals of granite and arkosic quartzite into a mineral assemblage consisting of various proportion of illite, chlorite, muscovite and pyrite, with the intensity of alterations being highest near to the unconformity. Pyrite is often associated with illite dominant alteration zone. We infer that circulation of basinal brine through basement granite and cover sediments was responsible for mobilising uranium from granite and its precipitation at favourable locations in cover sediments. Increase in pH of ore fluid due to illitisation and chloritisation of wallrock together with availability of carbonaceous matter and pyrite as reductant have controlled the localisation of uranium mineralisation in Banganapalle Formation.

Journal of Applied Geochemistry, 2014

Radioactive granitoids and cherty cataclasites are delineated in Thadisaoli–Khatgaon and Shahpur–... more Radioactive granitoids and cherty cataclasites are delineated in Thadisaoli–Khatgaon and Shahpur–Sujayatpur sectors in southeastern part of Nanded district, Maharashtra, which have recorded anomalous radioelemental contents (Granites: upto 1% U3O8 and 0.20% ThO2; Cherty cataclasites upto 0.11% U3O8 and <0.005% ThO2) and enrichment in trace element and rare metal and rare earth element concentration (Nb: upto 146ppm, Y: upto 226ppm, Zr: upto 559ppm and total REE: upto 2010ppm). The mineralised granitoids are affected by profuse pegmatitic/quartzo-feldspathic, quartz and epidote venations and mainly confined along the NE–SW and NNE–SSW faults/shear zones. Radioactive phases are represented by discrete uranium/thorium ore minerals (uraninite, -uranophane and thorite) and high content of resistates viz., apatite, zircon, allanite, sphene, cerianite, monazite and ilmenite. Fluid inclusion studies of the mineralised and sheared granites, quartzo-feldspathic veins (QFVs) and quartz veins indicate the presence of 6 to 32µm size aqueous and carbonic inclusions of three principle types and represented by six phases viz., aqueous mono-, bi- and poly-phase, aqueous-carbonic, carbonic mono- and poly-phase. Aqueous biphase inclusions show wide range of salinity (0.71 to 19.99 wt.% eNaCl) and homogenisation temperatures (Th: 127.5–280.8ºC ) while aqueous-carbonic inclusions exhibit restricted salinity (5–8.4 wt.% eNaCl ) and Th (28.3–30.9ºC). The composition of these aqueous fluids varies from NaCl–KCl dominant in quartz veins and radioactive granite to MgCl2 dominant in sheared radioactive granite. Similarly, co-eval aqueous biphase and aqueous-carbonic inclusions have yielded 678–958 bar pressure and 201–233ºC temperature in quartz vein samples while higher values of 1120–1550 bar and 304–360ºC are indicated by sheared granite. The presence of more than one population without much change in fluid composition signifies their origin at different stages of deformation. Besides, mixing of a moderate temperature and low salinity fluid (meteoric/basinal brine) with a comparatively high temperature and hypersaline fluid (magmatic/evolved brine) might have also played important role in inclusion characteristics. Based on these fluid inclusion characteristics, it appears that multi-episodic hydrothermal activity under extensional tectonic regime in this fertile granitic province has led to precipitation of uranium along suitable structural aureoles from uraniferous hydrotherms.

Journal of Asian Earth Sciences, Vol. 90, pp. 280-288, Sep 2014

Unconformity related uranium mineralisation occurs in Banganapalle Formation of Palnad Sub-basin,... more Unconformity related uranium mineralisation occurs in Banganapalle Formation of Palnad Sub-basin, Cuddapah Basin. Several evidences of hydrothermal activity exist in both basement granite and the cover sediments in Koppunuru and Rallavagu Tanda (R.V. Tanda) uranium prospects of Palnad Sub-basin. Profuse development of fracture filled veins consisting of epidote–quartz, chlorite–quartz and quartz is observed at various depths above and below unconformity. Fluid–rock interaction during the formation of these veins has resulted in the alteration of feldspars and mafic minerals of granite and arkosic quartzite into a mineral assemblage consisting of various proportion of illite, chlorite, muscovite and pyrite, with the intensity of alterations being highest near to the unconformity. Pyrite is often associated with illite dominant alteration zone. We infer that circulation of basinal brine through basement granite and cover sediments was responsible for mobilising uranium from granite and its precipitation at favourable locations in cover sediments. Increase in pH of ore fluid due to illitisation and chloritisation of wallrock together with availability of carbonaceous matter and pyrite as reductant have controlled the localisation of uranium mineralisation in Banganapalle Formation.

Journal of Earth System Science, 2021

Uranium mineralization occurs adjacent to the unconformity between Paleoproterozoic granite and M... more Uranium mineralization occurs adjacent to the unconformity between Paleoproterozoic granite and Meso- to Neoproterozoic cover sediments in Chitrial prospect of Cuddapah Basin in Indian shield. Hydrothermal activity in the granite is evident by the presence of hydrothermal veins and associated wallrock alteration in the unconformity zone (0–5 m below unconformity), shallow zone (5–100 m), and deep zone (100–120 m). Hydrothermal alteration of granite has produced chlorite in all depth, epidote in the deep zone, muscovite commonly in the shallow zone and illite predominantly in the unconformity zone. Pitchblende and coffinite are associated with sulphides and carbonaceous matter filling micro fractures and occurring along grain boundaries in the granite. Fluid inclusion study of quartz from hydrothermal veins reveals the presence of primary aqueous inclusions (biphase, monophase, polyphase) with a wide range of salinity from 0.2 to >23.2 wt.% (low–high). The fluid composition indica...

Journal of Asian Earth Sciences, 2014

ABSTRACT Unconformity related uranium mineralisation occurs in Banganapalle Formation of Palnad S... more ABSTRACT Unconformity related uranium mineralisation occurs in Banganapalle Formation of Palnad Sub-basin, Cuddapah Basin. Several evidences of hydrothermal activity exist in both basement granite and the cover sediments in Koppunuru and Rallavagu Tanda (R.V. Tanda) uranium prospects of Palnad Sub-basin. Profuse development of fracture filled veins consisting of epidote–quartz, chlorite–quartz and quartz is observed at various depths above and below unconformity. Fluid–rock interaction during the formation of these veins has resulted in the alteration of feldspars and mafic minerals of granite and arkosic quartzite into a mineral assemblage consisting of various proportion of illite, chlorite, muscovite and pyrite, with the intensity of alterations being highest near to the unconformity. Pyrite is often associated with illite dominant alteration zone. We infer that circulation of basinal brine through basement granite and cover sediments was responsible for mobilising uranium from granite and its precipitation at favourable locations in cover sediments. Increase in pH of ore fluid due to illitisation and chloritisation of wallrock together with availability of carbonaceous matter and pyrite as reductant have controlled the localisation of uranium mineralisation in Banganapalle Formation.

Journal of Applied Geochemistry, Vol. 16(4), pp. 361-380, Oct 1, 2014

Radioactive granitoids and cherty cataclasites are delineated in Thadisaoli–Khatgaon and Shahpur–... more Radioactive granitoids and cherty cataclasites are delineated in Thadisaoli–Khatgaon and Shahpur–Sujayatpur sectors in southeastern part of Nanded district, Maharashtra, which have recorded anomalous radioelemental contents (Granites: upto 1% U3O8 and 0.20% ThO2; Cherty cataclasites upto 0.11% U3O8 and <0.005% ThO2) and enrichment in trace element and rare metal and rare earth element concentration (Nb: upto 146ppm, Y: upto 226ppm, Zr: upto 559ppm and total REE: upto 2010ppm). The mineralised granitoids are affected by profuse pegmatitic/quartzo-feldspathic, quartz and epidote venations and mainly confined along the NE–SW and NNE–SSW faults/shear zones. Radioactive phases are represented by discrete uranium/thorium ore minerals (uraninite, -uranophane and thorite) and high content of resistates viz., apatite, zircon, allanite, sphene, cerianite, monazite and ilmenite.
Fluid inclusion studies of the mineralised and sheared granites, quartzo-feldspathic veins (QFVs) and quartz veins indicate the presence of 6 to 32µm size aqueous and carbonic inclusions of three principle types and represented by six phases viz., aqueous mono-, bi- and poly-phase, aqueous-carbonic, carbonic mono- and poly-phase. Aqueous biphase inclusions show wide range of salinity (0.71 to 19.99 wt.% eNaCl) and homogenisation temperatures (Th: 127.5–280.8ºC ) while aqueous-carbonic inclusions exhibit restricted salinity (5–8.4 wt.% eNaCl ) and Th (28.3–30.9ºC). The composition of these aqueous fluids varies from NaCl–KCl dominant in quartz veins and radioactive granite to MgCl2 dominant in sheared radioactive granite. Similarly, co-eval aqueous biphase and aqueous-carbonic inclusions have yielded 678–958 bar pressure and 201–233ºC temperature in quartz vein samples while higher values of 1120–1550 bar and 304–360ºC are indicated by sheared granite. The presence of more than one population without much change in fluid composition signifies their origin at different stages of deformation. Besides, mixing of a moderate temperature and low salinity fluid (meteoric/basinal brine) with a comparatively high temperature and hypersaline fluid (magmatic/evolved brine) might have also played important role in inclusion characteristics. Based on these fluid inclusion characteristics, it appears that multi-episodic hydrothermal activity under extensional tectonic regime in this fertile granitic province has led to precipitation of uranium along suitable structural aureoles from uraniferous hydrotherms.

Journal of Asian Earth Sciences, 2014

ABSTRACT Unconformity related uranium mineralisation occurs in Banganapalle Formation of Palnad S... more ABSTRACT Unconformity related uranium mineralisation occurs in Banganapalle Formation of Palnad Sub-basin, Cuddapah Basin. Several evidences of hydrothermal activity exist in both basement granite and the cover sediments in Koppunuru and Rallavagu Tanda (R.V. Tanda) uranium prospects of Palnad Sub-basin. Profuse development of fracture filled veins consisting of epidote–quartz, chlorite–quartz and quartz is observed at various depths above and below unconformity. Fluid–rock interaction during the formation of these veins has resulted in the alteration of feldspars and mafic minerals of granite and arkosic quartzite into a mineral assemblage consisting of various proportion of illite, chlorite, muscovite and pyrite, with the intensity of alterations being highest near to the unconformity. Pyrite is often associated with illite dominant alteration zone. We infer that circulation of basinal brine through basement granite and cover sediments was responsible for mobilising uranium from granite and its precipitation at favourable locations in cover sediments. Increase in pH of ore fluid due to illitisation and chloritisation of wallrock together with availability of carbonaceous matter and pyrite as reductant have controlled the localisation of uranium mineralisation in Banganapalle Formation.

Journal of Applied Geochemistry, 2014

Radioactive granitoids and cherty cataclasites are delineated in Thadisaoli–Khatgaon and Shahpur–... more Radioactive granitoids and cherty cataclasites are delineated in Thadisaoli–Khatgaon and Shahpur–Sujayatpur sectors in southeastern part of Nanded district, Maharashtra, which have recorded anomalous radioelemental contents (Granites: upto 1% U3O8 and 0.20% ThO2; Cherty cataclasites upto 0.11% U3O8 and <0.005% ThO2) and enrichment in trace element and rare metal and rare earth element concentration (Nb: upto 146ppm, Y: upto 226ppm, Zr: upto 559ppm and total REE: upto 2010ppm). The mineralised granitoids are affected by profuse pegmatitic/quartzo-feldspathic, quartz and epidote venations and mainly confined along the NE–SW and NNE–SSW faults/shear zones. Radioactive phases are represented by discrete uranium/thorium ore minerals (uraninite, -uranophane and thorite) and high content of resistates viz., apatite, zircon, allanite, sphene, cerianite, monazite and ilmenite. Fluid inclusion studies of the mineralised and sheared granites, quartzo-feldspathic veins (QFVs) and quartz veins indicate the presence of 6 to 32µm size aqueous and carbonic inclusions of three principle types and represented by six phases viz., aqueous mono-, bi- and poly-phase, aqueous-carbonic, carbonic mono- and poly-phase. Aqueous biphase inclusions show wide range of salinity (0.71 to 19.99 wt.% eNaCl) and homogenisation temperatures (Th: 127.5–280.8ºC ) while aqueous-carbonic inclusions exhibit restricted salinity (5–8.4 wt.% eNaCl ) and Th (28.3–30.9ºC). The composition of these aqueous fluids varies from NaCl–KCl dominant in quartz veins and radioactive granite to MgCl2 dominant in sheared radioactive granite. Similarly, co-eval aqueous biphase and aqueous-carbonic inclusions have yielded 678–958 bar pressure and 201–233ºC temperature in quartz vein samples while higher values of 1120–1550 bar and 304–360ºC are indicated by sheared granite. The presence of more than one population without much change in fluid composition signifies their origin at different stages of deformation. Besides, mixing of a moderate temperature and low salinity fluid (meteoric/basinal brine) with a comparatively high temperature and hypersaline fluid (magmatic/evolved brine) might have also played important role in inclusion characteristics. Based on these fluid inclusion characteristics, it appears that multi-episodic hydrothermal activity under extensional tectonic regime in this fertile granitic province has led to precipitation of uranium along suitable structural aureoles from uraniferous hydrotherms.

Journal of Asian Earth Sciences, Vol. 90, pp. 280-288, Sep 2014

Unconformity related uranium mineralisation occurs in Banganapalle Formation of Palnad Sub-basin,... more Unconformity related uranium mineralisation occurs in Banganapalle Formation of Palnad Sub-basin, Cuddapah Basin. Several evidences of hydrothermal activity exist in both basement granite and the cover sediments in Koppunuru and Rallavagu Tanda (R.V. Tanda) uranium prospects of Palnad Sub-basin. Profuse development of fracture filled veins consisting of epidote–quartz, chlorite–quartz and quartz is observed at various depths above and below unconformity. Fluid–rock interaction during the formation of these veins has resulted in the alteration of feldspars and mafic minerals of granite and arkosic quartzite into a mineral assemblage consisting of various proportion of illite, chlorite, muscovite and pyrite, with the intensity of alterations being highest near to the unconformity. Pyrite is often associated with illite dominant alteration zone. We infer that circulation of basinal brine through basement granite and cover sediments was responsible for mobilising uranium from granite and its precipitation at favourable locations in cover sediments. Increase in pH of ore fluid due to illitisation and chloritisation of wallrock together with availability of carbonaceous matter and pyrite as reductant have controlled the localisation of uranium mineralisation in Banganapalle Formation.