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P. Raase ¹, M. Raith ², D. Ackermand ¹, M. N. Viswanatha ³, R. K. Lal ⁴

Affiliations
1 Meneralogisch-Petrographisches Institut, der Universitat Olshausenstr, 40-60, D 2300 Kiel, DE
2 Mineralogisch-Petrologisches Institut, der Universitat Bonn, Poppelsdorfer Schloss, D 5300 Bonn, DE
3 Geological Survey of India, Southern Region, Hyderabad 500001, IN
4 Department of Geology, Banaras Hindu University, Varanasi 221005, IN

Abstract

The mineralogy of chromiferous quartzites from Archaean greenstone belts of southern Peninsular India has been studied. The majority of the quartzites are metamorphosed clastic sediments derived from a sialic source with enclaves of ultramafic chromite-bearing rocks. For the quartzites from the Ghatti Hosahalli belt, however, a volcanic-exhalative origin is most likely. The chromium in the sediments was fixed in the detrital chromite and/or the clay minerals.

The typical mineral assemblages developed in a wide range of metamorphic conditions from greenschist to amphibolite facies comprise fuchsite, quartz, kyanite and accessory rutile, tourmaline and Cr-spinel. Microprobe analyses show high chromium contents for fuchsite (2-4wt. % Cr₂O₃), kyanite (up to 6wt. % Cr₂O₃), rutile (1.0-2-6wt. % Cr₂O₃) and tourmaline (2.5-7.6 wt. % Cr₂O₃). Cr-spinels are essentially solid solutions between hercynite and chromite (Mg/(Mg+Fe²⁺)=0.060.15; Cr/(Cr+Al)=0.42-0.75). Comparison with igneous chromites indicates that compositional reequilibration during metamorphism was characterised by replacement of Mg by Fe²⁺ and, to a lesser extent, of Cr³⁺ by Al. The micas of chromiferous quartzites from the Chitradurga area have high Cr and Ba contents (1.4-3.9wt. % Cr₂O₃; 0.5-8.5 wt. % BaO) and represent solid solutions extending from muscovite to Cr-oellacherite, A baryte-bearing quartzite from the Ghatti Hosahalli belt contains the rare assemblage quartz, baryte, celsian (Cs₈₅Or₁₁Ab₄), fuchsite (15 wt. % Cr₂O₃; 8.5 wt. % BaO), uvarovite (Uv₇₁Gro₂₈) and tremolite.

The regular distribution of chromium between mica and associated Cr-spinel, rutile and tourmaline indicates equilibration during metamorphism.

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S. B. Dwivedi ¹, A. Mohan ¹, R. K. Lal ¹

Affiliations
1 Department of Geology, Banaras Hindu University, Varanasi-221 005, IN

Abstract

Reactions involving garnet, cordierite, aluminosilicate and quartz in FMASH system are calibrated as geothermobarometers, namely 1/2 Fe-crd + 1/3 Pyrope = 1/2 Mg-crd + 1/3 Almandine (1); 2 Almandine + 4 sillimanite/andalusite + 5 quartz = 3 Fe-crd (2 and 4); and 2 Pyrope + 4 sillimanite/andalusite + 5 quartz = 3 Mg-crd (3 and 5).

T = [6170+O.031(P-1)-400(X_Fe-X_Mg)^Crd-A]/(RlnK_D+2.812+B) (1)

A= 166 X²_Mg-506 X²_Fe+680 X_FeX_Mg+336 (X_Ca+X_Ma) (X_Mg-X_Fe)-

X_Ca - 358 X_Mn and B = 1.5 X_Ca

For Fe and Mg end-member reactions involving sillimanite, the following geobarometric formulation is obtained:

P_Fe=1+[{(24.02-6RlnK_Fe)T-17369}/4.003]                                  (2)

P_Mg=1+[{(7.238-6RlnK_Mg)T+19640}/3.82]                                  (3)

Similarly for reactions involving and alusite, P_Fe and P_Mg expressions are : P_Fe=1+[{(26.04-6RlnK_Fe)T-19471}/3.86]                                    (4)

P_Mg = 1+[{(9.25-6RlnK_Mg)T+17536}/3.68)                                  (5)

Keywords

Geothermobarometry, Metapelites, Metamorphism.

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Sonali Kumari ¹, Shweta Srivastava ², Ashok Mittal ³, R. K. Lal ⁴

Affiliations
1 Department of ECE, Birla Institute of Technology, Mesra, Ranchi – 835215, Jharkhand, IN
2 Jaypee Institute of Information Technology, Noida – 201309, Uttar Pradesh, IN
3 G. B. Pant Engineering College, Okhla Phase III – 110020, New Delhi,, IN
4 Department of ECE, Birla Institute of Technology, Mesra, Ranchi – 835215, Jharkhand

Abstract

Objective: The prime objective of the proposed work is to design a single antenna on low cost FR4 substrate that will work for multiband frequencies with improved gain. It provides acceptable return loss at 2GHz, 2.76GHz, 3.47GHz, 4.57GHz and 5.35GHz.Method/Analysis-A power-divider is used to form an array of two elements. In this paper, a T-junction power divider is used. For making a power-divider the three-port network is used for power division. In this design one input line is later divided into two parallel lines. Antenna is attached at the output of both the ends. For simulation HFSS(High Frequency Structure Simulator)version 13 is used. HFSS is very accurate and easy software for antenna designing. Findings-In this design, initially a simple sierpinski structure is modified. In place of a triangular patch, annular ring is designed and etched out from the structure. This process is continued upto 2nd iteration. Two such antennas are attached through equal-split power divider. The simple triangular patch with modifications (annular shape) is firstly simulated and later with use of power divider (T-shaped power divider). With use of power divider same antenna works for multiband frequencies and providing good gain. Microstrip feed has been used for feeding the antennas. Novelty-This unique antenna will work for RFID, W-Lan, Wi-Fi applications. Single antenna work for multiband frequency.

Keywords

Annular ring, Array, Fractal, HFSS, Power-Divider, Sierpinski

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