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31.
Dyutiman Choudhary Bishnu H. Pandit S. P. Kala N. P. Todaria S. Dasgupta Michael Kollmair 《社会与自然资源》2014,27(10):1057-1073
This article highlights the results of an action research to upgrade mountain farmers of bay leaf (Cinnamomum tamala Nees and Eberm) in Udayapur district of Nepal. Farmers received low prices, lacked market information, capacities, and institutional mechanisms, and were exploited by traders. To address these constraints, three independent but interlinked pro-poor value chain (VC) upgrading strategies comprising VC coordination upgrading and horizontal and vertical contractualization were implemented. Information was collected from focus-group discussions with collectors, traders, and facilitators, and a questionnaire was used to collect pre- and postintervention data (n = 120). VC upgrading strategies improved harvesting practices, increased farmers’ bargaining power, and led to a threefold increase in price, which increased household incomes. Results demonstrated improved terms of participation of farmers and a general increase in market price of bay leaf in Udayapur. The study approach can be up scaled to reduce poverty from high value products. 相似文献
32.
We have experimentally investigated melting phase relation of a nominally anhydrous, carbonated pelitic eclogite (HPLC1) at
2.5 and 3.0 GPa at 900–1,350°C in order to constrain the cycling of sedimentary carbon in subduction zones. The starting composition
HPLC1 (with 5 wt% bulk CO2) is a model composition, on a water-free basis, and is aimed to represent a mixture of 10 wt% pelagic carbonate unit and
90 wt% hemipelagic mud unit that enter the Central American trench. Sub-solidus assemblage comprises clinopyroxene + garnet + K-feldspar + quartz/coesite + rutile + calcio-ankerite/ankeritess. Solidus temperature is at 900–950°C at 2.5 GPa and at 900–1,000°C at 3.0 GPa, and the near-solidus melt is K-rich granitic.
Crystalline carbonates persist only 50–100°C above the solidus and at temperatures above carbonate breakdown, carbon exists
in the form of dissolved CO2 in silica-rich melts and as a vapor phase. The rhyodacitic to dacitic partial melt evolves from a K-rich composition at near-solidus
condition to K-poor, and Na- and Ca-rich composition with increasing temperature. The low breakdown temperatures of crystalline
carbonate in our study compared to those of recent studies on carbonated basaltic eclogite and peridotite owes to Fe-enrichment
of carbonates in pelitic lithologies. However, the conditions of carbonate release in our study still remain higher than the
modern depth-temperature trajectories of slab-mantle interface at sub-arc depths, suggesting that the release of sedimentary
carbonates is unlikely in modern subduction zones. One possible scenario of carbonate release in modern subduction zones is
the detachment and advection of sedimentary piles to hotter mantle wedge and consequent dissolution of carbonate in rhyodacitic
partial melt. In the Paleo-NeoProterozoic Earth, on the other hand, the hotter slab-surface temperatures at subduction zones
likely caused efficient liberation of carbon from subducting sedimentary carbonates. Deeply subducted carbonated sediments,
similar to HPLC1, upon encountering a hotter mantle geotherm in the oceanic province can release carbon-bearing melts with
high K2O, K2O/TiO2, and high silica, and can contribute to EM2-type ocean island basalts. Generation of EM2-type mantle end-member may also
occur through metasomatism of mantle wedge by carbonated metapelite plume-derived partial melts. 相似文献
33.
In this study, we investigate the possible record of a Late Mesoproterozoic paired metamorphic belt in the Aravalli-Delhi Mobile Belt(ADMB), NW India using a suite of supracrustal and metaigneous granulites from the Pilwa-Chinwali granulite terrain at the north-western margin of the ADMB. Using metamorphic reaction textures, mineral chemistry, metamorphic reaction history, geothermobarometric computations and electron microprobe dating of monazite in 5 samples of pelitic granulite, leptynite gneiss, enderbite and charnockite, we have deduced a medium-pressure granulite facies metamorphism(P between 4.9 and 6.8 kbar, T 760-815℃) along a heating-cooling, counterclockwise P-T path between 1.09 and 1.01 Ga. When collated with published metamorphic and chronological constraints and geological settings of the adjoining crustal domains of the ADMB, these findings provide new insights into the developments of two tectonic domains of contrasting thermal gradients at ca. 1.0 Ga, consistent with metamorphic transformations in tectonically thickened middle-lower crustal sections during continental collision to continental subduction and in the root zones of spatially adjacent island arc, as part of the Rodinia supercontinent assembly event. 相似文献
34.
Santanu Banerjee Shovan Lal Chattoraj P. K. Saraswati Somnath Dasgupta Urbashi Sarkar Adam Bumby 《Geological Journal》2012,47(4):357-371
An integrated study of the sedimentology, micropalaeontology, mineralogy and geochemistry of glauconites in the Oligocene Maniyara Fort Formation (western Kutch, India), has been undertaken. Authigenic glauconites, mostly of evolved type, formed within a back‐barrier lagoonal environment. Foraminifera help constrain the biostratigraphy and along with sedimentological evidence, provide information on the depositional conditions. Glauconite in the Maniyara Fort Formation occurs either as infillings within intra‐particle pores of larger foraminifers, or as an altered form of faecal pellets. X‐ray diffraction studies reveal the less mature nature of glauconite infillings compared to the glauconite pellets. Electron microprobe investigation confirms a relative enrichment of K2O and total Fe2O3 in the latter. Both varieties of glauconite formed by initial authigenic precipitation of K‐poor glauconite and subsequently matured by addition of potassium in the interlayer sites and fixation of total iron in the octahedral sites; calcium, magnesium and aluminum were released from the glauconite structure concomitantly. Alkaline conditions during the entire process of glauconite formation did not allow dissolution of foraminiferal tests. Mineralogical and chemical characteristics of the Maniyara Fort Formation glauconites are more similar to deep marine glauconites than those reported from other shallow or marginal marine settings. A low negative cerium anomaly, as well as abundant pyrite, suggests formation of glauconite in sub‐oxic micro‐environments, created by decay of organic matter associated with foraminiferal chambers and faecal pellets. Sub‐oxic condition apparently prevailed relatively longer within the Maniyara Fort Formation lagoons. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
35.
36.
Rajat Acharya Bijoy Roy M.R. Sivaraman Ashish Dasgupta 《Journal of Atmospheric and Solar》2010,72(9-10):774-780
The variability of Total Electron Content (TEC) at Trivandrum, located within equatorial anomaly region at the dip equator, with respect to a reference level derived from the TEC measurements at Shimla, located outside the region has been studied during low solar activity period. Chapman function is assumed to hold good for regions outside the anomaly extent. It shows that the difference of total measured TEC at the equator from the derived reference is highly correlated with equatorial electrojet. The observations conform to the previous investigations and are interpreted in light of established relations. A stochastic relationship with electrojet is derived and validated. 相似文献
37.
The seismotectonic characteristics of 1983–1984, 1993 and 2005 swarms in Andaman Sea are analysed. These swarms are characterised
by their typical pulsating nature, oval shaped geometry and higher b values. The migration path of the swarms from north to south along the Andaman Spreading Ridge is documented. While the first
two swarms are located along existing mapped rift segments, the 2005 swarm appears to have generated a new rift basin along
8°N. The analysis and supporting evidences suggest that these swarms were generated by intruding magmatic dyke along the weak
zones in the crust, followed by rifting, spreading and collapse of rift walls. CMT solutions for 2005 swarm activity indicate
that intrusion of magmatic dyke in the crustal weak zone is documented by earthquakes showing strike slip solution. Subsequent
events with normal fault mechanism corroborate the rift formation, collapse and its spreading. 相似文献
38.
39.
Exsolution textures in orthopyroxene in aluminous granulites as indicators of UHT metamorphism: New evidence from the Eastern Ghats Belt, India 总被引:1,自引:0,他引:1
Highly aluminous orthopyroxene, coexisting with sapphirine, cordierite, sillimanite, quartz and garnet in various combinations, constitute granoblastic mosaic peak metamorphic assemblages in aluminous granulites from three localities in the Eastern Ghats Belt, India. Orthopyroxene contains four types of intergrowths: (a) involving sapphirine with or without cordierite, (b) involving spinel, but without sapphirine, (c) involving cordierite, but without sapphirine and spinel, and (d) involving garnet, without sapphirine, spinel or cordierite. On the basis of textural and compositional data, origin of the intergrowths is ascribed to breakdown of Mg-Tschermak component, locally also involving Fe- and Ti-Tschermak. An attempt is made to compute the “pre-breakdown” compositions of orthopyroxene by image analysis, which shows maximum Al2O3 content of 13.4 wt.% in the pristine orthopyroxene. Geothermometry, phase equilibria consideration and application of existing experimental data on alumina solubility in orthopyroxene coexisting with sapphirine and quartz, collectively indicate extreme thermal conditions of metamorphism (> 1000 °C) for the studied assemblages. This re-affirms the notion that Al2O3 solubility in orthopyroxene is the most powerful indicator of UHT metamorphism (Harley, S.L., 2004. Extending our understanding of ultrahigh temperature crustal metamorphism. J. Mineral. Petrol. Sci. 99, 140–158). The intergrowths are considered to have formed due to cooling from the thermal peak spanning a temperature range of approximately 150 °C. Appearance of diverse types of intergrowths is probably related to subtle differences in bulk composition, particularly Fe:Mg ratios. 相似文献
40.
A refined garnet - biotite Fe−Mg exchange geothermometer and its application in amphibolites and granulites 总被引:4,自引:0,他引:4
Somnath Dasgupta Pulak Sengupta Dipayan Guha M. Fukuoka 《Contributions to Mineralogy and Petrology》1991,109(1):130-137
A new formulation of garnet-biotite Fe–Mg exchange thermometer has been developed through statistical regression of the reversed experimental data of Ferry and Spear. Input parameters include available thermo-chemical data for quaternary Fe–Mg–Ca–Mn garnet solid solution and for excess free energy terms, associated with mixing of Al and Ti, in octahedral sites, in biotite solid solution. The regression indicates that Fe–Mg mixing in biotite approximates a symmetrical regular solution model showing positive deviation from ideality withW
FeMg
bi
=1073±490 cal/mol. H
r
and S
r
for the garnet-biotite exchange equilibrium were derived to be 4301 cal and 1.85 cal respectively. The resultant thermometer gives consistent results for rocks with a much wider compositional range than can be accommodated by earlier formulations. 相似文献