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During drilling at Borg, ca. 5 km southwest of central Norrköping, an unidentified fine-grained grey rock was encountered in contact with dark red granitic gneiss at 35m depth. The fine-grained grey rock occurs above the red granitic gneiss. Our understanding prior to testing is that the rock may have been formed by fluid alteration of a mafic rock, as neither metamorphic nor sedimentary textures were observed. Understanding this rock and the formation processes related to it, is of interest for the general understanding of the region and of geotechnical importance since fracture fillings may affect the stability of the rock during and after construction projects. This study uses the methods petrography, XRD and XRF to define the fine-grained mafic rock, black vein in the fine-grained mafic rock, the contact zone and the granitic gneiss. Results show that the fine-grained grey rock has a composition of muscovite (36.1%), quartz (24.6%), albite (20.8%), sericite (10.8) and montmorillonite (0.5%). The contact is mainly made of quartz veins and calcite veins. The protolith of the fine-grained mafic rock is suggested to be iron-rich. Further testing on additional unaltered mafic rock samples from the area would provide a more accurate picture of the protolith evolution.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22051号 / 工博第4632号 / 新制||工||1722(附属図書館) / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 岸田 潔, 教授 木村 亮, 教授 小池 克明 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM