Basaltic pillow lavas near the Kazhaba village in Balochistan are found in the tectonic slivers of the Bagh complex： the melange zone beneath the Muslim Bagh ophiolite complex. These volcanics are mainly represented ...Basaltic pillow lavas near the Kazhaba village in Balochistan are found in the tectonic slivers of the Bagh complex： the melange zone beneath the Muslim Bagh ophiolite complex. These volcanics are mainly represented by alkali basalts. The petrography and chemistry suggest that these volcanic rocks belong to mildly to strongly alkaline, intra-plate volcanic rock series. Their low Mg~# and low Cr, Ni and Co contents suggest that the parent magma of these volcanics was not directly derived from a partially melted mantle source, but resulted fractionation in an upper level magma chamber, en-route to eruption. Their LILE and HFSE, enriched primordial mantle-normalized patterns with marked positive Nb anomalies further confirm their within-plate geochemical signatures and are consistent with an enriched mantle source. Their highly enriched LREE patterns and high（La/Yb）_N and（Ce/Yb）_N ratios suggest a partially melted garnet-lherzolite parent magma source. The Zr versus Zr/Y studies suggest that these volcanics were derived from about 15% partially melted enriched mantle source. It is suggested that these Late Cretaceous intra-plate volcanics may represent the mantle plume activity of the Reunion hotspot, and were erupted during the passage of Ceno-Tethys Ocean floor prior to the passage of Indian Plate over it.展开更多
文摘Basaltic pillow lavas near the Kazhaba village in Balochistan are found in the tectonic slivers of the Bagh complex： the melange zone beneath the Muslim Bagh ophiolite complex. These volcanics are mainly represented by alkali basalts. The petrography and chemistry suggest that these volcanic rocks belong to mildly to strongly alkaline, intra-plate volcanic rock series. Their low Mg~# and low Cr, Ni and Co contents suggest that the parent magma of these volcanics was not directly derived from a partially melted mantle source, but resulted fractionation in an upper level magma chamber, en-route to eruption. Their LILE and HFSE, enriched primordial mantle-normalized patterns with marked positive Nb anomalies further confirm their within-plate geochemical signatures and are consistent with an enriched mantle source. Their highly enriched LREE patterns and high（La/Yb）_N and（Ce/Yb）_N ratios suggest a partially melted garnet-lherzolite parent magma source. The Zr versus Zr/Y studies suggest that these volcanics were derived from about 15% partially melted enriched mantle source. It is suggested that these Late Cretaceous intra-plate volcanics may represent the mantle plume activity of the Reunion hotspot, and were erupted during the passage of Ceno-Tethys Ocean floor prior to the passage of Indian Plate over it.
