Browsing by Author "Tahir, Muhammad Mohsin"

The Vihanti-Lampinsaari group in the Raahe-Ladoga belt, central Finland, hosts massive sulphide deposits. Host rocks are highly deformed and metamorphosed (amphibolite to granulite facies) felsic to intermediate volcanic rocks with minor mafic metavolcanics. Due to intense metamorphism, it is difficult to figure out the nature of the original protolith of hosts rocks and there is no systematic examination of the trace elements behaviour found in the literature for the rocks in the Lampinsaari region. Two main topics were studied: (1) The trace elements behaviour of the rocks in the Vihanti (Lampinsaari) group, and (2) origin of the volcanic rocks and volcanic architecture of the Vihanti group. Better knowledge on the geochemistry of the immobile trace elements in these highly metamorphosed rocks led to the more accurate and precise determination of the origin of volcanic rocks and their volcanic architecture. Igneous (Felsic-intermediate-mafic) metavolcanic rocks of the Vihanti-Lampinsaari region have all calc-alkaline magmatic affinity according to (Ross and Bedard; 2009) Zr vs Y and major elements classification by Miyashiro (1974). The chondrite normalized patterns of the trace elements having enriched concentrations of LREE relative to low HREE indicates island arc settings. There is no significant hydrothermal material present in metasedimentary rocks of the Vihanti Lampinsaari area. Meta-sedimentary rocks of the Vihanti group are largely silica-rich with the presence of detrital components. Two calc-silicate bearing paragneisses have higher concentrations of Fe which are due to the pyrite while three distinct samples with higher P₂O₅ having higher concentrations of Mn represents phosphate minerals. Negative Eu anomaly due to Ca-replacement and enriched LREE with respect to HREE is an indication of evolved source areas. Sedimentary carbonates with one rock type of serpentinite-dolomite are mineralized ones have a higher concentration of Mn and are enriched in FeO which is due to the hydrothermal alteration in the sediments. Volcanic sedimentary rocks are highly evolved in composition but show depletion in Ba, Ti and Sr. Investigated sulfide ore deposits of the Vihanti-Lampinsaari region have diverse REE behaviour in chondrite normalized patterns due to high fluid/rock ratios. Due to high fluid/rock ratios, it is more likely to lose parent texture of the rocks with dissimilar trends in primitive and chondritic normalized patterns. Positive anomalies of Eu represent ore mineralization and considered for better chances of ore-bearing rocks. While negative Eu anomalies indicate late-stage mineralization in these mineralized rocks of the Vihanti-Lampinsaari region.