TY - JOUR

T1 - Metasomatism of ferroan granites in the northern Aravalli orogen, NW India

T2 - Geochemical and isotopic constraints, and its metallogenic significance

AU - Kaur, Parampreet

AU - Chaudhri, Naveen

AU - Hofmann, Albrecht W.

AU - Raczek, Ingrid

AU - Okrusch, Martin

AU - Skora, Susanne

AU - Koepke, Jürgen

N1 - Funding Information: Acknowledgments We are grateful to Dmitry V. Kuzmin (Mainz), Uli Schuessler (Würzburg), nora Groschopf (Mainz) and Doris neu-häuser (Mainz) for their assistance in microprobe work, XRF analyses and clean laboratory, and Rosemarie Baur (Würzburg) for performing some of the XRF analyses. We thank two anonymous reviewers and the Editor Ingo Braun for their comments that led to improvement of the manuscript. Fruitful discussions with, and valuable suggestions by, Hartwig Frimmel (Würzburg) are warmly acknowledged. This work was supported by grants from the Department of Science and Technology, new Delhi (DST, SR/S4/ES-388/2008), and the German academic Exchange Service, Bonn (DaaD, a/03/02882).

PY - 2014/6

Y1 - 2014/6

N2 - The late Palaeoproterozoic (1.72-1.70 Ga) ferroan granites of the Khetri complex, northern Aravalli orogen, NW India, were extensively metasomatised ~900 Ma after their emplacement, at around 850-830 Ma by low-temperature (ca. 400 °C) meteoric fluids that attained metamorphic character after exchanging oxygen with the surrounding metamorphic rocks. Albitisation is the dominant metasomatic process that was accompanied by Mg and Ca metasomatism. A two-stage metasomatic model is applicable to all the altered ferroan intrusives. The stage I is represented by a metasomatic reaction interface that developed as a result of transformation of the original microcline-oligoclase (An12-14) granite to microcline-albite (An1-3) granite, and this stage is rarely preserved. In contrast, the stage II metasomatic reaction front, where the microcline-bearing albite granite has been transformed to microcline-free albite granite, is readily recognisable in the field and present in most of the intrusives. Some of them lack an obvious reaction interface due to the presence of stage II albite granites only. When studied in isolation, these intrusives were incorrectly classified and their tectonic setting was misinterpreted. Furthermore, our results show that the mafic mineralogy of metasomatised granites has a significant impact on the characterisation of such rocks in the magmatic classification and discrimination diagrams. Nevertheless, the stage I metasomatised granites can be appropriately characterised in these diagrams, whereas the characterisation of the stage II granites will lead to erroneous interpretations. The close spatial association of these high heat producing ferroan granites with iron oxide-copper-gold (IOCG), U and REE mineralisation in the region indicates a genetic link between the metasomatism and the mineralisation. World-class IOCG, U and REE deposits are associated with metasomatised ferroan granites, suggesting that such a relationship may act as a critical first-order exploration target for undiscovered mineral deposits.

AB - The late Palaeoproterozoic (1.72-1.70 Ga) ferroan granites of the Khetri complex, northern Aravalli orogen, NW India, were extensively metasomatised ~900 Ma after their emplacement, at around 850-830 Ma by low-temperature (ca. 400 °C) meteoric fluids that attained metamorphic character after exchanging oxygen with the surrounding metamorphic rocks. Albitisation is the dominant metasomatic process that was accompanied by Mg and Ca metasomatism. A two-stage metasomatic model is applicable to all the altered ferroan intrusives. The stage I is represented by a metasomatic reaction interface that developed as a result of transformation of the original microcline-oligoclase (An12-14) granite to microcline-albite (An1-3) granite, and this stage is rarely preserved. In contrast, the stage II metasomatic reaction front, where the microcline-bearing albite granite has been transformed to microcline-free albite granite, is readily recognisable in the field and present in most of the intrusives. Some of them lack an obvious reaction interface due to the presence of stage II albite granites only. When studied in isolation, these intrusives were incorrectly classified and their tectonic setting was misinterpreted. Furthermore, our results show that the mafic mineralogy of metasomatised granites has a significant impact on the characterisation of such rocks in the magmatic classification and discrimination diagrams. Nevertheless, the stage I metasomatised granites can be appropriately characterised in these diagrams, whereas the characterisation of the stage II granites will lead to erroneous interpretations. The close spatial association of these high heat producing ferroan granites with iron oxide-copper-gold (IOCG), U and REE mineralisation in the region indicates a genetic link between the metasomatism and the mineralisation. World-class IOCG, U and REE deposits are associated with metasomatised ferroan granites, suggesting that such a relationship may act as a critical first-order exploration target for undiscovered mineral deposits.

KW - Albitisation

KW - Aravalli orogen

KW - Ferroan granites

KW - IOCG metallogeny

KW - Khetri complex

KW - Metasomatism

KW - NW India

UR - http://www.scopus.com/inward/record.url?scp=84900014756&partnerID=8YFLogxK

U2 - 10.1007/s00531-014-1005-x

DO - 10.1007/s00531-014-1005-x

M3 - Article

AN - SCOPUS:84900014756

VL - 103

SP - 1083

EP - 1112

JO - International Journal of Earth Sciences

JF - International Journal of Earth Sciences

SN - 1437-3254

IS - 4

ER -