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Hari Shankar Pandalai Gajanan Narayanrao Jadhav Biju Mathew V. Panchapakesan K. Krishnam Raju M. L. Patil 《Mineralium Deposita》2002,38(5):597-624
The pressure, temperature and composition of ore fluids that resulted in gold deposition in the Archean, greenstone-hosted Hutti deposit have been studied using fluid inclusions and the compositions of arsenopyrite and chlorite. Five types of fluids have been identified in fluid inclusions in quartz veins associated with mineralization. They are (1) monophase CO 2-rich fluid; (2) low-salinity (0 to 14 wt% NaCl equivalent) and high-salinity (16 to 23 wt% NaCl equiv.) aqueous fluids; (3) high-salinity (28 to 40 wt% NaCl equiv.), polyphase aqueous fluids; (4) CO 2–H 2O–NaCl fluids of low salinity (0–8 wt% NaCl equiv.); and (5) a few carbonic inclusions with halite±nahcolite. The diversity of entrapped fluid composition is explained in terms of changes in fluid pressure and temperature which affect a more or less uniform supply of primary low-salinity CO 2–H 2O–NaCl fluid to the shear zone. Geothermobarometric studies indicate that during mineralization temperature ranged between 360 and 240 °C, and fluid pressure between 3,600 and 1,600 bar. The data are interpreted in terms of the cyclic fault-valve mechanism for active shear zones. Deposition of gold and sulfides has been studied on the basis of constraints from the composition of wall-rock chlorite, ore-mineral assemblages, and textural features. Tubular channels, 20 to 100 µm wide and up to 500 µm long that arise from fractures and C-planes in sheared quartz veins are reported for the first time. The channels have pyrrhotite, arsenopyrite, pyrite and gold at their distal ends, with calcite filling up the remaining part. These channels form in response to increases in T and P, by dissolution of quartz grains, guided by dislocations in them. At the P– T conditions of interest, gold and sulfide deposition takes place in the shears and fractures of quartz veins from CO 2–H 2O–NaCl ore fluid of low salinity and pH due to changes in phase compositions that occur during the process of shear failure of the enclosing rocks. In the wall rock where pH is buffered, gold deposition takes place from the predominant Au(HS) 2 - species with progressive sulfide deposition and decrease in SS, from 0.01 to 0.001 mol/kg as T falls from 360 to 240 °C. 相似文献
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An integrated process involving participatory and modelling approaches for prioritizing and evaluating climate change adaptation options for the Kangsabati reservoir catchment is presented here. We assess the potential effects of climate change on water resources and evaluate the ability of stakeholder prioritized adaptation options to address adaptation requirements using the Water Evaluation And Planning (WEAP) model. Two adaptation options, check dams and increasing forest cover, are prioritized using pair-wise comparison and scenario analysis. Future streamflow projections are generated for the mid-21st century period (2021–2050) using four high resolution (~25 km) Regional Climate Models and their ensemble mean for SRES A1B scenario. WEAP simulations indicate that, compared to a base scenario without adaptation, both adaptation options reduce streamflow. In comparison to check dams, increasing forest cover shows greater ability to address adaptation requirements as demonstrated by the temporal pattern and magnitude of streamflow reduction. Additionally, over the 30 year period, effectiveness of check dams in reducing streamflow decreases by up to 40 %, while that of forest cover increases by up to 47 %. Our study highlights the merits of a comparative assessment of adaptation options and we conclude that a combined approach involving stakeholders, scenario analysis, modelling techniques and multi-model projections may support climate change adaptation decision-making in the face of uncertainty. 相似文献
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Gajanan Kapure Chandrakala KariS. Mohan Rao N.D. Rao 《International Journal of Mineral Processing》2007
The Floatex density separator (FDS) is an industrial separator and works on the principle of hindered settling where the settling rate of a particle in suspension is affected by nearby particles. This phenomenon of hindered settling has been described by various authors using the concept of particle slip velocity. The feasibility of one such slip velocity model proposed by Galvin et al. to predict the separation of chromite in a plant scale FDS was examined. Previously this model was validated only at lab scale with synthetic mixture of various density particles. In order to use this model, the feed chromite ore was characterized and quantified into different density mineral classes and their percentages were estimated by using mineralogical grain count method. The performance of FDS was then predicted using slip velocity model in terms of weight recoveries and composition of different minerals in the FDS underflow product. 相似文献
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