Implications of the geochemistry of the Pelitic Granulites of the Delhi Supergroup, Aravalli Mountain Belt, Northwestern India

Abstract

An isolated granulite terrain occurs within the linear zone of schists and amphibolites of the Proterozoic Delhi Supergroup, in the Aravalli mountain belt of NW India. The geochemistry of the pelitic granulites of such terrains suggests the arkosic to shaley nature of the protolith. These rocks are characterized by a high maturity index, low to intermediate Fe 2O 3 + MgO values (5.78%), high La Sc (8.3), Th Sc (4.0) and Ni Co (1.4) ratios and, low Ti Zr (16), Sc Cr (0.16) and Sc Ni (0.16) ratios which imply a passive continental margin nature of the basin. The high K 2O value (3.0%), high K 2O Na 2 O ratio (1.96), LREE enrichment, flat HREE pattern, consistent negative Eu anomaly, high La cn Yb cn (10.6) and Th Sc (4.0) ratios and low La Th (2.4) ratio, low Ni (30 ppm) and Cr (47 ppm) contents, and uniform Zr Hf ratio largely reflect continental provenance and probable Proterozoic age. These rocks also differ from Archaean granulites of the fold belt with regards to K 2O and Th U values and deformational history.