Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

N. K. Saini ¹, K. K. Purohit ¹, M. S. Rathi ¹, P. P. Khanna ¹, Pulok Kr. Mukherjee ¹, Hakim Rai ¹

Affiliations
1 Wadia Institute of Himalayan Geology, 33-General Mahadeo Singh Road, Dehra Dun-248001, IN

Abstract

An attempt has been made to produce an international metabasic rock standard from the Rudraprayag Fonnation of Himalayan orogenic belt. The bulk sample collected has been processed and subjected to homogeneity test (F test). The salient petrographic features. proximate analysls and the F-ratio of the different fractions are presented in this paper.

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R. Islam ¹, K. K. Purohit ¹, V. C. Thakur ¹

Affiliations
1 Wadia Institute of Himalayan Geology, Dehra Dun - 248 001, IN

Abstract

On the basis of geochemical study, two granitic plutons are identified in the Bhilangna valley of the Garhwal Himalaya, viz. the Chaili porphyritic granite gneiss (CPGG) and the Ingedinala granite gneiss (IGG). Both, CPGG and IGG rocks fall in the quartz rich zone (QRZ) of chemical-mineralogical typology of Dcbon and Le Fort, 1982. CPGG and IGG are strongly peraluminous, S-type granites and enriched in Si and K and depleted in Ca and Sr. The unusually high K₂O suggests introduction of LILE during metasomatic processes. Both, CPGG and IGG are crustally derived and produced due to the partial melting of psammo-pelitic sediments. Probably the source materials for CPGG and IGG are same, attested by the geochemical similarities. The Q-Ab-Or plots of CPGG and IGG revealed that the temperature higher than that of the 'minimum' melt was attained during anatexis. During the Himalayan orogeny, intracontinental subduction took place along MCT and provided channels for the metasomatic fluids which induced K and Rb metasomatism and subsequently modified the nature of CPGG and IGG.

Keywords

Anatexis, Granitic Pluton, Garhwal Himalaya, Subduction, Main Central Thrust, Metasomatism.

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M. S. Rathi ¹, P. P. Khanna ¹, P. K. Mukherjee ¹, K. K. Purohit ¹, N. K. Saini ¹

Affiliations
1 Wadia Institute of Himalayan Geology, 33-General Mahadeo Singh Road, Dehra Dun, IN

Abstract

Proposal for the preparation of a metabasic reference sample (MB-H) from the Himalayas has attracted the participation of twenty four laboratories of repute from thirteen countries beside India. Tables of compiled data (1818 total individual results in all) are presented in this paper. Working values/information values have been assigned for 37 major, minor and trace elements including REEs after rigorous statistical as well as subjective data evaluation.

Keywords

Trace Elements, Statistics, Geochemistry, Geostandard.

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R. Islam ¹, K. S. Bist ¹, B. K. Chaudhuri ¹, B. S. Rawat ¹, K. K. Purohit ¹

Affiliations
1 Wadia Institute of Himalayan Geology, Dehra Dun-248001, IN

Abstract

A maiden attempt has been made to study the far-flung Hanuman Tibba Granites of Kullu valley, Himachal Pradesh. The granite has intruded the low grade Haimanta (-Lahaul) Formation which tectonically overlies the Rohtang Gneissic Complex. Integrated field, petrographic and geochemical studies have revealed that it is peraluminous S- type granite derived from sedimentary protolith. Compositional difference in terms of depletion of Fe, Mg, Ti, Ca, Sr, Zr and enhancement of Sit K and Rb from margin to core of the granite body is consistent with fractional crystallization process.

The emplacement of Hanuman Tibba Granite on the same tectonic level as Jispa and Ratilaman granite (500±ma) in adjacent Lahaul-Spiti region suggests a Cambro-Ordovician age for the Hanuman Tibba Granite.

Keywords

Petrology. Geochemistry, Hanuman Tibba Granite (HTG), Haimanta Formation, Kullu Valley, Himalaya.

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P. K. Mukherjee ¹, K. K. Purohit ¹, M. S. Rathi ¹, P. P. Khanna ¹

Affiliations
1 Wadia Institute of Himalayan Geology, 33, Gen Mahadeo Singh Road, Dehra Dun, 248001, IN

Abstract

A two mica granite body occurs in and around Dalhousie (Himachal Himalaya) as an intrusion into the core of an antiform at the southern flank of the Dhauladhar range. The rocks near the contact are enriched in biotite (bio>mus), whereas those of the core are more enriched in muscovite (mus>bio). Otherwise the major mineralogical make-up and their whole rock chemistry are monotonous. The rocks are weakly to moderately peraluminous in nature. The trace elemental characteristics are very similar to the average upper crust and follow more closely with the mean felsic S-type trend.

The low normative as well as calculated modal quartz and high Na_zO content suggest their origin from a less mature sedimentary source. The ubiquitous Eu anomaly, depleted Sr with enriched Rb and non-involvement of plagioclase or alkali feldspar in the fractionation model further implies that there was abundant feldspar in the source and more calcic plagioclase were left out in the residue that selectively retained Eu and SI- and released Rb in its early fraction of melts. It was noted that only -10% fractionation of solids mainly consisting of biotite and muscovite with minor amounts of feldspar are required to account for the major elemental mass balance requirement between the compositional differences. Whereas the depletion of REEs as well as other trace element abundances in the more . fractionated samples from the central part of the intrusion were modeled and attributed due to fractionation of minor quantity of REE enriched phases (∼1.5%) like monazite, apatite and zircon. However, the Zr requirement in this model is insufficient. Nevertheless, the observed nearly three times depletion in REEs, Zr, Th and P may be required to be explained in a similar way involving such REE sink accessory phases. The haplogranitic phase relations suggest that the emplacement of the granitic magma took place under water-sufficient condition at a shallower depth (-2-3kb.) whereas magma generated at relatively deeper level but restricted to a depth where plagioclase is stable rather than garnet. The water requirement was homogeneously made available internally by the breakdown of hydrous minerals like micas and a_H2O was sufficiently high. This also led to high oxidizing condition of the magma causing higher population of Eu³⁺ as compared to Eu²⁺ that might have behaved much similar to other adjacent MREEs (Sm and Gd) which occurs in 3+ state.

Keywords

Geochemistry, Petrogenesis, Granite, REE, Himachal Himalaya.

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N. K. Saini ¹, P. K. Mukherjee ¹, P. P. Khanna ¹, K. K. Purohit ¹

Affiliations
1 Wadia Institute of Himalayan Geology, Dehra Dun - 248 001, IN

Abstract

An amphibolite sample named as AM-H is the third candidate reference rock in the series of reference samples from Himalaya. First two geostandards already characterized in the series being MB-H (metabasic) and DG-H (granite), are now in use for routine analysis at several laboratories. The sample is being distributed to several participating laboratories and analysts for contribution of analytical data. The sample was tested for its suitability as a reference standard in terms of its bulk homogeneity using F-test carried out for 16 fractions of the sample analyzed in duplicate. The results of homogeneity test along with relevant information like, location, geological set-up, mineralogical makeup, petrography and expected chemical composition are given for the benefit of potential analyst/contributors. The proposed reference sample may prove useful for analysis of metabasics and intermediate igneous rocks with high Cr and lower abundances of elements like Ba, Na, K, P, Nb and Zr.

Keywords

Geochemistry, AM-H, Geostandard, Amphibolite, F-test, Himalaya.

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K. K. Purohit ¹, P. K. Mukherjee ¹, N. K. Saini ¹, M. S. Rathi ¹, P. P. Khanna ¹

Affiliations
1 Wadia Institute of Himalayan Geology, 33, Gen. Mahadeo Singh Road, Dehra Dun, 248 001, IN

Abstract

Geochemical characteristics of active stream and river sediment from part of the main Alaknanda catchment including main tributaries (Nandakini, Pindar and Mandakini) in Garhwal Himalaya were investigated. Economically important and environmentally sensitive selected trace element (Cr, Ni, Pb, Zn, Cu, Th and U) abundance in the sediments were studied to evaluate their spatial distribution in relation to lithotectonic control, mineral prospects and environmental geochemistry. The background concentrations, as median values, are found perceptibly enriched for these elements with respect to upper crustal average. Distribution patterns of U, Th and Pb are distinctive and show intrinsic relationship with the medium-grade deformed rocks (granitoids) of central crystallines and are generally enriched, whereas Cu is depleted in the same area. Background concentration of Cr is many fold enriched as compared to crustal abundance. 5 However, Ni in relation to Cr is not so high. There is a good correlation between Cr and Ni in the areas of mafic volcanic occurrences within low-grade metasedimentry rocks. But the same is not true in case of Nandakini valley within Baijnath central crystallines where Cr enrichment is anomalously high with Ni showing antagonistic relationship. High U and Th content in sediments are observed within or near the central crystalline thrust sheets, whereas the Cu and Zn anomaly zones are restricted within the Garhwal group of rocks. Some of these anomalies are significant and seems to have a definite structural (thrust/Fault) and lithological control, such as crystallines for U and Th and carbonates for Cu and Zn. The present study, thus also provides some useful clues for mineral exploration. Whereas the high anomaly areas are highly potential for economic mineral deposits of Cu, Zn, U and Th, but at the same time are equally prone to toxic exposure of U and Th as well as risk of arsenic and cadmium contamination that are normally associated with Cu and Zn sulphides.

Keywords

Trace element geochemistry, Heavy Metals, Stream Sediments, Background value, Mineralization, Environmental impact, Himalaya.

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N. K. Saini ¹, P. K. Mukherjee ¹, M. S. Rathi ¹, P. P. Khanna ¹, K. K. Purohit ¹

Affiliations
1 Wadia Institute of Himalayan Geology, Dehradun - 248 001, IN

Abstract

A new geochemical reference sample of Granite named as DG-H from Dalhousie, Himachal Pradesh is proposed for collaborative study. The sample has been tested for its suitability as a reference standard in terms of its bulk homogeneity using F-test carried out for 16 fractions of the sample analysed in duplicate. The relevant information like, location, geological set-up, mineralogical make-up, petrography, expected chemical composition and F-ratios derived for major oxides are given for the benefit of potential contributors and users. The proposed standard may prove useful for analysis of granitic rocks with high Cr and lower abundances of elements like Ba, Ca, Cu, Nb, Ni, Sr, Th, Y and Zr.

Keywords

Geochemistry, Granite, DG-H, Geostandard, F-Test, Himalaya.

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