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21.
22.
The nepheline-diopside join defines the ultra-alkaline portion of the basalt tetrahedron and the bulk composition of nephelinitic
rocks lie in this join. Schairer and others established that under atmospheric pressure, the join cuts through the primary
phase volumes of oliviness, carnegieitess and nepheliness. Melilite coexists with nepheliness, oliviness and diopsidess below 1160±10°C and olivine reacts out at low temperature.
Experimental studies on seven compositions show the presence of a pseudoeutectic at Ne70Di30 and 1420°C, where diopsidess, nepheliness and liquid are in equilibrium. Olivine and melilite do not appear in the system and the assemblage below 1225±20°C is diopsidess+nepheliness. 相似文献
23.
Alok Kumar Praveer Pankaj K. Koteswara Rao 《Journal of the Geological Society of India》2016,87(2):127-131
A singular outcrop of a lamproite dyke is located ~1.5 km south-west of Chintalapalle village at the NW margin of the Cuddapah basin, eastern Dharwar craton, southern India.. The dyke trends E-W and is emplaced within the granitic rocks belonging to the peninsular gneissic complex. The lamproite dyke has a porphyritic to weakly porphyritic texture comprising microphenocrysts of sanidine, and potassic richterite set in a groundmass rich in carbonate, and chlorite with rutile and titanate as accessory phases. This new occurrence of lamproite is located mid-way between the well-known Narayanpet kimberlite field towards the west and the Ramadugu and Vattikod lamproite fields in east. The Chintalapalle lamproite dyke, together with those from Vattikod, Ramadugu, Krishna and Cuddapah basin lamproite fields, constitute a wide spectrum of ultrapotassic magmatism emplaced in and around the Palaeo-Mesoproterozoic Cuddapah basin in southern India. 相似文献
24.
The high-resolution Bay of Bengal circulation modeling in the region [80E–95E; 5N–22N] is performed with a horizontal resolution of 10 km and the highest vertical resolution of 5 m near the surface. The intercomparison experiments, with ocean model forced with the near-surface (1) National Centers for Environmental Prediction (NCEP) reanalysis winds and (2) blended seawinds data (a combination of remotely sensed scatterometer and in situ observations) are carried out for a period of 17 years during 1998–2014. The seasonal variability of the realistically simulated surface hydrographic (temperature and salinity) and circulation (currents) variables from both the experiments is compared and contrasted with the observational data. The mixed layer depth seasonal variability of the region is also studied. The mesoscale features of currents at 50 and 100 m are also studied. The volume transport across different sections in the Bay of Bengal is computed and its relation with summer monsoon rainfall is investigated. The results suggest that there is no real advantage of using high-resolution blended seawinds over the much coarser NCEP reanalysis winds. 相似文献
25.
26.
Natural Hazards - A network of 25 lightning detection sensors (LDS) has been established by the National Remote Sensing Centre (NRSC), the Indian Space Research Organization (ISRO). At present,... 相似文献
27.
Natural Hazards - Glacial lakes are rapidly growing in response to climate change and glacier retreat which may lead to catastrophic socio-economic disasters. The failure of moraine-dammed lakes is... 相似文献
28.
Arti Goyal Gopal-Krishna G. C. Anupama D. K. Sahu R. Sagar S. Britzen M. Karouzos † M. F. Aller H. D. Aller 《Monthly notices of the Royal Astronomical Society》2009,399(3):1622-1632
We present the result of our extensive intranight optical monitoring of the well-known low-energy peaked BL Lac (LBL) object PKS 0735+178. This long-term follow-up consists of R -band monitoring for a minimum duration of ∼4 hours, on 17 nights spanning 11 years (1998–2008). Using the CCD as an N-star photometer, a detection limit of around 1 per cent was attained for the intranight optical variability (INOV). Remarkably, an INOV amplitude of ≥3 per cent on hour-like time-scale was not observed on any of the 17 nights, even though the likelihood of a typical LBL showing such INOV levels in a single session of ≳4 hours duration is known to be high (∼50 per cent) . Our observations have thus established a peculiar long-term INOV quiescence of this radio-selected BL Lac object. Moreover, the access to unpublished optical monitoring data of similarly high sensitivity, acquired in another programme, has allowed us to confirm the same anomalous INOV quiescence of this LBL all the way back to 1989, the epoch of its historically largest radio outburst. Here, we present observational evidence revealing the very unusual INOV behaviour of this classical BL Lac object and discuss this briefly in the context of its other known exceptional properties. 相似文献
29.
Jian Bai Alok Porwal Craig Hart Arianne Ford Le Yu 《Journal of Geochemical Exploration》2010,104(1-2):1-11
Most conventional statistical methods aiming at defining geochemical concentration thresholds for separating anomalies from background have limited effectiveness in areas with complex geological settings. This paper uses multifractal analysis to combine the characteristics of geochemical frequency distribution and spatial dispersion in order to map geochemical singularities instead of using conventional statistically derived concentration thresholds. The model, termed radius–areal Productivity (r–P) model, employs a stable measure and a scale-increasing method to estimate geochemical singularities spatially on geochemical landscape for delineating potential anomalies. The model is applied to geochemical data of regional stream sediments from the Funin Sheet, Yunnan, China. 相似文献
30.
The system diopside-nepheline-leucite, representing a join in the undersaturated part of the system nepheline (Ne)-kalsilite (Ks)-CaO-MgO-SiO2, has been investigated at atmospheric pressure. The system is pseudoternary and cuts the primary phase volumes of forsterite solid solution (Foss), diopside solid solution (Diss), nepheline solid solution (Ness), carnegieite solid solution (Cgss), and leucite solid solution (Lcss). Melilite (Mel) occurs as a subliquidus phase. The phase diagram has two four-phase points: 1. one at 1275±5° C and Di60Ne8Lc32 where liquid coexists with Foss, Diss and Lcss, corresponding to olivine (Ol) leucitite; 2. the other at 1194±5° C and Di27.5Ne29.5Lc43 where Ness, Foss and Lcss coexist with liquid, corresponding to Ol-Ne italite. With decreasing temperature, liquid moves from point (1) to a five-phase assemblage (3) where liquid is in equilibrium with Foss, Diss, Mel and Lcss (1258±5°C), which is representative of Ol-Mel-leucitite. From point (2) liquid moves to a second five-phase assemblage (4), where Foss, Mel, Ness, Lcss and liquid are in equilibrium (1175±5°C, corresponding to a Lc-Ne katungite. The assemblage Foss+Ness+Diss+Mel+Lcss+ liquid, is reached between 1168° and 1100° C and corresponds to Ol-Mel-Ne leucitite. Foss reacts with liquid and disappears. Near the point (1) it disappears at 1135±10° C, whereas near the point (2) it reacts out at 1060±10° C. Near the join Di-Ne it disappears at 950±10° C. The final assemblage in the system is representative of Mel-Ne leucitite.Presented at the symposium Recent Advances in the Studies of Rocks and Minerals at High Pressures and Temperatures held in Montreal, 1972. Jointly sponsored by the International Mineralogical Association and the Commission on Experimental Petrologie. 相似文献