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The petrography, mineralization, and geochemistry and isotope studies of sulfide ores were used to determine the genesis of the Naweoba and Bagh Volcanogenic Massive Sulfide (VMS) deposits. These deposits consist of minor stockwork, massive sulfide, and gossan zones. They are hosted by basaltic rocks in the Naweoba Block and Bagh Complex of Zhob Valley Ophiolites, respectively. The host rocks are strongly altered to chlorite and sericite. By using whole rock and pyrite in situ analyses, it is found that the Cu concentration is higher compared to Zn and Pb. Similarly, the primary mantle normalized data of Pb, Cu, Ag, Au, and Zn as well as the high Co/Ni ratios (> 1) in pyrite for both deposits indicate that these deposits have a mafic origin dominated by hydrothermal processes. The trace element signature in pyrite and chalcopyrite in these deposits suggests that mineralization formed at high to moderate temperatures. The δ34S values of pyrite (2.4–4.6‰) and chalcopyrite (2.7–5.7‰) indicate that hydrothermal fluids have derived sulfur largely from basaltic igneous rocks. The above signatures are all consistent with a Cyprus-type VMS ore deposits associated with ophiolites. Moreover, it was found that several trace elements (Ni, Co, Se, Zn, Pb, Sb, and As) show systematic variations in pyrite from Naweoba that are correlated to the stratigraphic depth and can be used as a proxy to separate deeper from shallower sulfide ores. [ABSTRACT FROM AUTHOR]

The Zhob ophiolite comprises the Naweoba, Omzha and Ali Khanzai blocks, which are surrounded by the sediments of the Alozai Group and Loralai Formation. The Ali Khanzai Block contains metamorphic, ultramafic, gabbroic, volcanic and volcaniclastic rocks with associated chert. The Zhob manganese deposits found in the Ali Khanzai Block, occur in banded, lenticular and massive forms within red to brown coloured metachert. Braunite and pyrolusite are the main constituent manganese-bearing minerals with minor hausmannite, hematite and barite while quartz is the major gangue mineral with some carbonate minerals. Geochemical evidence from the major oxides indicates that the manganese mineralization and associated metachert at Zhob were formed by hydrothermal activity with little contribution from contemporaneous volcanic materials and this is confirmed by high Fe/Mn and low Co/Zn ratios and trace element patterns. These deposits formed along with seafloor spreading centres and were later obducted as part of Ali Khanzai Block of Zhob ophiolite. [ABSTRACT FROM AUTHOR]

The Sillai Patti Carbonatite Complex constitutes the second largest carbonatite complex in Pakistan. However, our current understanding of its origin and geodynamic settings remains unclear. An integrated investigation, involving mineral composition, titanite U Pb dating, whole-rock geochemistry and C O isotopes as well as in situ Sr Nd isotope study of the mineral calcite and titanite from this carbonatite complex was conducted. The carbonatite, mainly consisting of calcite, apatite, amphibole and biotite, occurs as a sheet-like intrusion along an NNE-SSW-striking and southward dipping thrust plane. Titanite U Pb dating results reveal that the Sillai Patti carbonatites were formed at about 83 ± 7 Ma. Chemically, the Sillai Patti carbonatites are characterized by variably high SiO 2 (4.56–24.02 wt%), P 2 O 5 (3.32–6.09 wt%) and total REEs contents (1989–3309 ppm) and are enriched in alkalis (Na 2 O > K 2 O), Nb (29–397 ppm), Zr, Ba, Sr and LREEs. The elevated contents of REEs and Nb and the ubiquitous REE-Nb mineral hosts (e.g., fluorapatite (up to 1.8 wt% LREE 2 O 3), titanite (up to 7360 ppm REE and 10,050 ppm Nb), calcite (350–760 ppm REE), allanite, pyrochlore, zircon and monazite) in the Sillai Patti carbonatites suggest that they have considerable potential of REEs and Nb mineralization. δ13C PDB and δ18O SMOW values for the Sillai Patti carbonatites vary from −6.7 ‰ to −6.9 ‰ and 8.3 ‰ to 10.4 ‰, respectively, which are in good agreement with primary mantle-derived carbonatite values. The Sillai Patti carbonatites show slightly enriched Sr and Nd isotopic compositions ((87Sr/86Sr) i = 0.70472–0.70496; εNd(t) = −2.6 to −0.1), indicating derivation from an enriched sub-continental lithospheric mantle source. We propose that the Sillai Patti carbonatites were formed in an intra-continental rift setting. Along with other analogous Late Cretaceous carbonatites and alkaline silicate rocks in the northwestern margin of the Indian plate, they likely recorded an early period of alkaline magmatism related to the Réunion hotspot mantle plume. • Titanite U-Pb dating yielded ca. 83 Ma for the Sillai Patti carbonatites. • The carbonatites are products of partial melts of an enriched SCLM source. • The Sillai Patti carbonatites occurred during intra-continental rift setting. • Chronicle Réunion hotspot is invoked to contribute to the source of magmatism. [ABSTRACT FROM AUTHOR]