Deep Drilling in Crystalline Bedrock: The Deep Gas Drilling in the Siljan Impact Structure, Sweden and Astroblemes: Exploration of the Deep Continental Crust

General Papers.- Siljan Drilling Experiment: Participation of the Gas Research Institute.- Preparatory Investigations — an Overview.- The Deep Earth Gas Theory with Respect to the Results from the Gravberg-1 Well.- Major Questions About Deep Continental Structures.- Conclusions — Exploratory Work.- Technical Papers.- Gravberg-1: Well Design and Drilling Preparations.- Scientific Programme of Well Investigations — an Overview.- Drilling of the Gravberg-1 — Review and Operational Problems.- Scientific Papers.- The Gravity Field of the Siljan Ring Structure.- Electrical Conductivity Structure Around the Gravberg Well.- Early Results of the Electric Wireline Logging in the Gravberg-1 Well.- Interpretation of the Seismic Reflectors in the Gravberg-1 Well.- Geochemical Studies, Gravberg-1 Well, Sweden; Integration of Well Site and External Laboratory Analyses.- Analysis of Gases in the Gravberg-1 Well.- Light Hydrocarbons in Drill Cuttings from the Gravberg-1 Borehole.- Trace Elements in Gravberg Drillhole Samples.- Calcite Crack Cements in Granite from the Siljan Ring, Sweden: Stable Isotopic Results.- Fluid Inclusions in Granite from the Siljan Ring Impact Structure and Surrounding Regions.- Low Temperature Alterations in Granitic Rocks from the Siljan Ring Structure, Central Sweden.- Mössbauer Spectroscopic Data of Granitic Rocks from Gravberg-1 Well, Siljan Ring Structure, Central Sweden.- Investigations of Rocks from the Gravberg-1 Well: Petrological and Geochemical Results.- Geochemical Logging in the Siljan Ring.- Capture of Deep Earth Gas in Water-Filled Fractures.- Astroblemes.- Physical Aspects on Cratering and Slumping.- Structural Deformation, Breccia Formation, and Shock Metamorphism in the Basement of Complex Terrestrial Impact Craters: Implications forthe Cratering Process.- Possible Impact Structures in Sweden.- The Formation of Large Impact Structures and Constraints on the Nature of Siljan.- Geological Setting of the Siljan Ring Structure.- Deep Crustal Structure in the Vicinity of the Siljan Ring.