Academia.eduAcademia.edu

Figure 1 – uploaded by Prasanta Kumar Mishra

See full PDFdownloadDownload figure
Fig. 1. Outline map of India showing different Purana basins (modified after Ramakrishnan and Vaidyanadhan, 2010). AC: Aravalli Craton, BC: Bastar Craton, BKC Bundelkhand Craton, DC: Dharwar Craton and SC: Singhbhum Craton. Details of the rectangular framed area (Bastar craton) are shown in Fig. 2. The Indian shield consists of five Archean cratonic nuclei (Fig. 1; The Bastar Craton, one of the oldest craton in Indian Peninsula (Fig. 2), consists of diverse rock assemblages consisting of older gneisses, greenstone belts, and granitoids of Archean age covered by Proterozoic basins (Fermor, 1936; Crookshank, 1963; Sarkar et al., 1990; Ghosh, 2004). The oldest rocks of the craton include tonalite-trondhjemite- granodiorite (TTG) gneisses of 3561 + 11 Ma and K-rich granites, the

Figure 1 Outline map of India showing different Purana basins (modified after Ramakrishnan and Vaidyanadhan, 2010). AC: Aravalli Craton, BC: Bastar Craton, BKC Bundelkhand Craton, DC: Dharwar Craton and SC: Singhbhum Craton. Details of the rectangular framed area (Bastar craton) are shown in Fig. 2. The Indian shield consists of five Archean cratonic nuclei (Fig. 1; The Bastar Craton, one of the oldest craton in Indian Peninsula (Fig. 2), consists of diverse rock assemblages consisting of older gneisses, greenstone belts, and granitoids of Archean age covered by Proterozoic basins (Fermor, 1936; Crookshank, 1963; Sarkar et al., 1990; Ghosh, 2004). The oldest rocks of the craton include tonalite-trondhjemite- granodiorite (TTG) gneisses of 3561 + 11 Ma and K-rich granites, the

Related Figures (21)

Fig. 2. Generalised geological map of the Bastar Craton (after Ramachandra, 2004). Framed area with red border is shown as Fig. 3. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 2. Generalised geological map of the Bastar Craton (after Ramachandra, 2004). Framed area with red border is shown as Fig. 3. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 3. Generalised geological map of the Chilpi Group (modified after Ramachandra and Roy, 2001; Geological Survey of India, 2006). Details of the framed area a the center are shown in Fig. 4.
Fig. 3. Generalised geological map of the Chilpi Group (modified after Ramachandra and Roy, 2001; Geological Survey of India, 2006). Details of the framed area a the center are shown in Fig. 4.
Fig. 4. Detailed lithological map of the study area showing sample locations.
Fig. 4. Detailed lithological map of the study area showing sample locations.
Fig. 5. Lithostratigraphic column of the Chilpi Group. Dip corrected sectior showing maximum thickness of the units (present work), and sample location ir the dolomite unit.
Fig. 5. Lithostratigraphic column of the Chilpi Group. Dip corrected sectior showing maximum thickness of the units (present work), and sample location ir the dolomite unit.
Stratigraphy of the study area (modified after Thawait et al., 2014). Table 1
Stratigraphy of the study area (modified after Thawait et al., 2014). Table 1
Fig. 6. Photomicrographs of the Chilpi carbonate: (a) preservation of primary lamination in dolomite with fabric retention texture, (b) fine grained micritic dolomite (under plane polarized light), (c) very fine grained circular to elliptical oolite consisting of carbonate mineral (dolomite), surrounded by fine to medium grains of dolomite showing granular texture (under plane polarized light), (d) fine to medium grained crystalline polymodal dolomite crystals (under crossed nicols). (e) fine to medium grained secondary quartz vein in the dolomite host rock (under crossed nicols). (f) Back-scattered Electron (BSE) image showing two varieties of dolomite: (i) circular to elliptical oolites of uniform dolomitic composition, with borders sealed by quartz grains and (ii) compositionally mixed dolomite, ferroan dolomite and ankerite with associated quartz and chamosite. (Note: Dol - Dolomite, Qtz — Quartz, Chm - chamosite, Ank - Ankerite, Fer dol —- Ferroan Dolomite, Qtz vein — Quartz vein).
Fig. 6. Photomicrographs of the Chilpi carbonate: (a) preservation of primary lamination in dolomite with fabric retention texture, (b) fine grained micritic dolomite (under plane polarized light), (c) very fine grained circular to elliptical oolite consisting of carbonate mineral (dolomite), surrounded by fine to medium grains of dolomite showing granular texture (under plane polarized light), (d) fine to medium grained crystalline polymodal dolomite crystals (under crossed nicols). (e) fine to medium grained secondary quartz vein in the dolomite host rock (under crossed nicols). (f) Back-scattered Electron (BSE) image showing two varieties of dolomite: (i) circular to elliptical oolites of uniform dolomitic composition, with borders sealed by quartz grains and (ii) compositionally mixed dolomite, ferroan dolomite and ankerite with associated quartz and chamosite. (Note: Dol - Dolomite, Qtz — Quartz, Chm - chamosite, Ank - Ankerite, Fer dol —- Ferroan Dolomite, Qtz vein — Quartz vein).
differentiate the detrital input in pure chemical sediments (Viehmann et al., 2015). The Y/Ho vs. Nd plot for the Chilpi carbonates (Fig. 10) indicates low concentration of Nd and samples are more towards pure chemical precipitates without detrital contaminations. The positive Y (i. e. Y/Ho weight ratio > 26), Gd/Gd*, La/La* anomalies further indicate preservation of pristine marine water signatures. Thus, most of the samples are indeed free from significant detrital contamination. Constant Y/Ho ratio of ~ 26 is characteristic features to terrestrial materials and therefore a small addition of crustal material can mask the seawater like Y/Ho ratio and would lead to co-variation between Y/Ho - Ce/Ce* and Zr - Y/Ho (Bolhar et al., 2004). The plots of Al, Th, Sc, and Zr versus XREE, Y/Ho and Ce/Ce* (Fig. 9a-l) were examined critically to assess possibilities of detrital contamination. The detrital phases and XREE show poor negative correlations for Al-ZREE (Fig. 9a), weak correlation for Sc-XREE (Fig. 9g) and moderate correlation for Zr-XREE (Fig. 9j) and Th-ZREE (Fig. 9d). As Y/Ho values could get depressed due to addition of detrital phases, it is expected to develop negative corre- lation with detrital components (Al, Th, Sc and Zr), which get enriched due to addition of crustal material. The correlations between these phases are poor (Th-Y/Ho, Fig. 9e and Zr-Y/Ho, Fig. 9k) and moderately negative (Y/Ho-Al, Fig. 9b and Y/Ho-Sc, Fig. 9h). As Sc value in all the samples, and Th value in many samples are very low (<2 ppm and < 0.5 ppm, respectively), detrital contamination is negated for the sample, which is further substantiated by poor to moderate correlation between Ce/Ce* - Al, Ce/Ce* - Th, Ce/Ce* - Sc, and Ce/Ce* - Zr (Fig. 9 ¢, f, i, and j). The cross plots of Y/Ho vs. Nd concentration can be used to Marine or freshwater derived carbonate can be monitored for oxide and sulfide contamination by comparing Y/Ho ratio (as the seawater signal) against Cu or Ni that are preferably incorporated into oxides, and Sc or Pb that are preferably incorporated into sulfides (Bolhar and Van Kranendonk, 2007; Wang et al., 2018). The relatively low concentra- tions of Ni and Sc, and the poor correlation between Y/Ho ratio and Ni (figure not given) and negative correlation between Y/Ho ratio and Sc (Fig. 9h) contents in the carbonate suggest that contamination by oxides and sulfides was insignificant. Similarly contamination from phosphates was evaluated by correlating P and ZREE. The low P contents and very poor correlation between P and ZREE suggest limited influence of phosphates (Fig. 11a). Further, phosphate leaching causes enrichment of
differentiate the detrital input in pure chemical sediments (Viehmann et al., 2015). The Y/Ho vs. Nd plot for the Chilpi carbonates (Fig. 10) indicates low concentration of Nd and samples are more towards pure chemical precipitates without detrital contaminations. The positive Y (i. e. Y/Ho weight ratio > 26), Gd/Gd*, La/La* anomalies further indicate preservation of pristine marine water signatures. Thus, most of the samples are indeed free from significant detrital contamination. Constant Y/Ho ratio of ~ 26 is characteristic features to terrestrial materials and therefore a small addition of crustal material can mask the seawater like Y/Ho ratio and would lead to co-variation between Y/Ho - Ce/Ce* and Zr - Y/Ho (Bolhar et al., 2004). The plots of Al, Th, Sc, and Zr versus XREE, Y/Ho and Ce/Ce* (Fig. 9a-l) were examined critically to assess possibilities of detrital contamination. The detrital phases and XREE show poor negative correlations for Al-ZREE (Fig. 9a), weak correlation for Sc-XREE (Fig. 9g) and moderate correlation for Zr-XREE (Fig. 9j) and Th-ZREE (Fig. 9d). As Y/Ho values could get depressed due to addition of detrital phases, it is expected to develop negative corre- lation with detrital components (Al, Th, Sc and Zr), which get enriched due to addition of crustal material. The correlations between these phases are poor (Th-Y/Ho, Fig. 9e and Zr-Y/Ho, Fig. 9k) and moderately negative (Y/Ho-Al, Fig. 9b and Y/Ho-Sc, Fig. 9h). As Sc value in all the samples, and Th value in many samples are very low (<2 ppm and < 0.5 ppm, respectively), detrital contamination is negated for the sample, which is further substantiated by poor to moderate correlation between Ce/Ce* - Al, Ce/Ce* - Th, Ce/Ce* - Sc, and Ce/Ce* - Zr (Fig. 9 ¢, f, i, and j). The cross plots of Y/Ho vs. Nd concentration can be used to Marine or freshwater derived carbonate can be monitored for oxide and sulfide contamination by comparing Y/Ho ratio (as the seawater signal) against Cu or Ni that are preferably incorporated into oxides, and Sc or Pb that are preferably incorporated into sulfides (Bolhar and Van Kranendonk, 2007; Wang et al., 2018). The relatively low concentra- tions of Ni and Sc, and the poor correlation between Y/Ho ratio and Ni (figure not given) and negative correlation between Y/Ho ratio and Sc (Fig. 9h) contents in the carbonate suggest that contamination by oxides and sulfides was insignificant. Similarly contamination from phosphates was evaluated by correlating P and ZREE. The low P contents and very poor correlation between P and ZREE suggest limited influence of phosphates (Fig. 11a). Further, phosphate leaching causes enrichment of
Ratio of element composition of the carbonate of the Chilpi Group. Table 3
Ratio of element composition of the carbonate of the Chilpi Group. Table 3
Fig. 7. Multielement spider diagram of the carbonate rocks of the Chilpi Group. Note: PASS normalized concentrations are plotted on a logarithmic scale.
Fig. 7. Multielement spider diagram of the carbonate rocks of the Chilpi Group. Note: PASS normalized concentrations are plotted on a logarithmic scale.
Fig. 8. PAAS-normalised REE + Y patterns of studied carbonates of the Chilpi Group. Note: PAAS-normalised concentrations are plotted on a logarithmic scale. abundance (Frimmel, 2009). Increasing consensus and major studies suggest that REE + Y behave stable during diagenesis (Kamber et al., 2014; Gilleaudeau et al., 2018). Thus, diagenetic alteration is insignif- icant in evaluating different parameters in the samples of analysed carbonates. (figure not given); moderate correlation between Fe and Ce/Ce* (Fig. 12a); Fe and Y/Ho (Fig. 12b), and no correlation between Fe and Eu/Eu* (Fig. 12c). Mn content has patterns similar to that of Fe (Fig. 12d, e, f). All the samples of the Chilpi Group (except one) are characterized by Lapass/ Ybpass and Lapass/ Lupass values of < 1 (Table 3) indicating these to be HREE enriched and of marine origin. Thus, the loss of HREE due to metamorphism is insignificant. Further, the metamorphism has not affected to the carbonates as indicated by lack of variation in correlation diagrams, preservation of positive Y anomaly (Y/Ho > 26), Gd/Gd* and high molar Y/Ho value. All pa- rameters, thus, indicate that metamorphism has minimal effect or no effect on the carbonates. Further, a moderate positive correlation be- tween Fe and Ce/Ce* and poor correlation for Fe and Eu/Eu* suggest that metamorphic processes are also insignificant (Bau, 1991).
Fig. 8. PAAS-normalised REE + Y patterns of studied carbonates of the Chilpi Group. Note: PAAS-normalised concentrations are plotted on a logarithmic scale. abundance (Frimmel, 2009). Increasing consensus and major studies suggest that REE + Y behave stable during diagenesis (Kamber et al., 2014; Gilleaudeau et al., 2018). Thus, diagenetic alteration is insignif- icant in evaluating different parameters in the samples of analysed carbonates. (figure not given); moderate correlation between Fe and Ce/Ce* (Fig. 12a); Fe and Y/Ho (Fig. 12b), and no correlation between Fe and Eu/Eu* (Fig. 12c). Mn content has patterns similar to that of Fe (Fig. 12d, e, f). All the samples of the Chilpi Group (except one) are characterized by Lapass/ Ybpass and Lapass/ Lupass values of < 1 (Table 3) indicating these to be HREE enriched and of marine origin. Thus, the loss of HREE due to metamorphism is insignificant. Further, the metamorphism has not affected to the carbonates as indicated by lack of variation in correlation diagrams, preservation of positive Y anomaly (Y/Ho > 26), Gd/Gd* and high molar Y/Ho value. All pa- rameters, thus, indicate that metamorphism has minimal effect or no effect on the carbonates. Further, a moderate positive correlation be- tween Fe and Ce/Ce* and poor correlation for Fe and Eu/Eu* suggest that metamorphic processes are also insignificant (Bau, 1991).
Fig. 9. Cross-plots of geochemical data of the carbonates for validation of detrital contribution. (a) Al vs. REE, (b) Al vs. Y/Ho, (c) Al vs. Ce/Ce*, (d) Th vs. ZREE, (e) Th vs. Y/Ho, (f) Th vs. Ce/Ce*, (g) Sc vs. ZREE, (h) Sc vs. Y/Ho, (i) Sc vs. Ce/Ce*, (j) Zr vs. ZREE, (k) Zr vs. Y/Ho, (1) Zr vs. Ce/Ce*.
Fig. 9. Cross-plots of geochemical data of the carbonates for validation of detrital contribution. (a) Al vs. REE, (b) Al vs. Y/Ho, (c) Al vs. Ce/Ce*, (d) Th vs. ZREE, (e) Th vs. Y/Ho, (f) Th vs. Ce/Ce*, (g) Sc vs. ZREE, (h) Sc vs. Y/Ho, (i) Sc vs. Ce/Ce*, (j) Zr vs. ZREE, (k) Zr vs. Y/Ho, (1) Zr vs. Ce/Ce*.
Fig. 10. Y/Ho vs. Nd concentration for the Chilpi carbonates. Low concentration of Nd indicates samples are pure chemical precipitates without detrital contam. inations (detritus and chondrite trends are adopted from Viehmann et al., 2015).
Fig. 10. Y/Ho vs. Nd concentration for the Chilpi carbonates. Low concentration of Nd indicates samples are pure chemical precipitates without detrital contam. inations (detritus and chondrite trends are adopted from Viehmann et al., 2015).
Fig. 11. Cross-plots of geochemical data of the carbonates for validation of phosphate leaching, diagenesis and Ba interference. (a) P vs. REE, (b) P vs. MREE/ MREE*, and (c) Ba/Nd vs. Eu/Eu*.
Fig. 11. Cross-plots of geochemical data of the carbonates for validation of phosphate leaching, diagenesis and Ba interference. (a) P vs. REE, (b) P vs. MREE/ MREE*, and (c) Ba/Nd vs. Eu/Eu*.
Fig. 12. Cross-plots of geochemical data of carbonates for assessing diagenesis, alteration and metamorphism. (a) Fe vs. Ce/Ce*, (b) Fe vs. Y/Ho, (c) Fe vs. Eu/Eu*, (d) Mn vs. Ce/Ce*, (e) Mn vs. Y/Ho, (f) Mn vs. Eu/Eu*.
Fig. 12. Cross-plots of geochemical data of carbonates for assessing diagenesis, alteration and metamorphism. (a) Fe vs. Ce/Ce*, (b) Fe vs. Y/Ho, (c) Fe vs. Eu/Eu*, (d) Mn vs. Ce/Ce*, (e) Mn vs. Y/Ho, (f) Mn vs. Eu/Eu*.
Table 5 Fig. 13. Cross-plots of geochemical data of carbonates for assessing paleo-redox conditions. (a) Cr/V vs. Ni/Co , (b) V/(V + Ni) vs. Ni/Co, (c) U/Th vs. Ni/Co. Field: of oxic, suboxic and anoxic conditions are shown by yellow, dark gray and light gray shade, respectively. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Table 5 Fig. 13. Cross-plots of geochemical data of carbonates for assessing paleo-redox conditions. (a) Cr/V vs. Ni/Co , (b) V/(V + Ni) vs. Ni/Co, (c) U/Th vs. Ni/Co. Field: of oxic, suboxic and anoxic conditions are shown by yellow, dark gray and light gray shade, respectively. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 14. Characterisation of Ce-anomaly in the carbonates. The field boundaries and calculations of Ce* and Pr* are adopted from Bau and Dulski (1996). I = Real negative Ce anomaly; II = Positive La anomaly, produces apparent negative Ce anomaly; III = Neither Ce nor La anomaly; IV = Positive La anomaly, disguises a positive Ce anomaly; V = Real positive Ce anomaly; and VI = Negative La anomaly, no Ce anomaly.
Fig. 14. Characterisation of Ce-anomaly in the carbonates. The field boundaries and calculations of Ce* and Pr* are adopted from Bau and Dulski (1996). I = Real negative Ce anomaly; II = Positive La anomaly, produces apparent negative Ce anomaly; III = Neither Ce nor La anomaly; IV = Positive La anomaly, disguises a positive Ce anomaly; V = Real positive Ce anomaly; and VI = Negative La anomaly, no Ce anomaly.
Related topics:
Earth SciencesGeologyGeochemistryPrecambrian GeologyBanded Iron FormationCrustal evolutionGreat Oxidation Event
580 California St., Suite 400
San Francisco, CA, 94104
© 2025 Academia. All rights reserved