PETROLOGY, GEOCHEMISTRY AND STRUCTURE OF MAFIC-ULTRAMAFIC ROCKS, PAGEDONGAN AREA, BANJARNEGARA, JAWA TENGAH

• Main Author: JUNDULLOH - NIM : 22014306, IREV
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/28114
• Institution: Institut Teknologi Bandung

<p align="justify">The research area is located in Pagedongan, Banjarnegara, Central Java. This study is based on a field data collection and laboratory analyses. <br /> <br /> The distribution of mafic-ultramafic rocks of study area indicates a certain sequence, i.e, respectively (from south to north) consisting of basalt, diabase, massive gabbro, layered gabbro, lherzholite, harzburgite and peridotite which have been serpentinized. It has been hydrothermal altered and metamorphisms are characterized by actinolite, tremolite, prehnite, chlorite, epidote, zoisite and zeolite minerals belonging to the zeolites and greenschists facies produced by oceanic floor metamorphisms, The boundary rocks is contacted by tectonic structures. <br /> <br /> Based on whole rock geochemical data shows tholeiitic affinity as indicated by the increase concentration in FeO along with the decreasing MgO content on AFM diagram, The co-magmatic signatures shown by the alignment patterns on the Harker diagram. The volcanic rocks in the study area plotted using elements Zr, Y, and Nb from Meschede (1989). Rare earth elements normalized to primitive mantle from Sun and McDonough (1995) indicate a relative increase pattern of light rare earths elements are about ten times primitive mantle and gradually flat pattern of heavy rare earth element. Thus, it is suggest that the mafic-ultramafic rocks are The Ophiolite Complexes classified into dismembered and metamorphised ophiolites. <br /> <br /> Microstructure of mafic-ultramafic rocks is possible by using microscopic observation. The textural features of the rock which indicate particular rocks formation. Deformation mechanism developed in the study area were formed in cataclasis zone, consisting of microcrack, impingment microcrack, micro-fault-induced microcracks and microfault. In addition, there are deformation mechanisms in diffusive mass transfer zone (DMT) is microvein, then, deformation mechanisms in intracrystalline plasticity zone, consisting of undulatory extinction, twin boundary migration, kink band and recrystallization consisting of bulging, subgrain rotation and grain boundary migration.<p align="justify">