This GeoGuide provides an overview of the geology of Alnö, combined with an up-to-date field itinerary. Covering all major geological aspects, it offers an essential summary of Alnö and its intriguing magmatic rocks in a compact form suitable for field excursions and home study alike. As one of the type localities for carbonatite, the late Proterozoic Alnö ring complex has been a crucial site for carbonatite-related research (next to the Fen complex in Norway), and provided one of the earliest test beds for this unique group of igneous rocks. Five geological excursions introduce the visitor to the most rewarding outcrops, including detailed descriptions and a wealth of high-quality colour photographs. The excursions are complemented by a detailed review of the history of scientific investigation on Alnö and, in particular, a catalogue of exotic and common minerals associated with the complex’s carbonatitic and alkaline silicate rocks. Finally, a summary of its trace element and isotope geochemistry as well as a brief outlook on Alnö’s potential as a future source of Rare Earth Elements (REEs) completes the book.

Fifty years ago, Tuzo Wilson published his paper asking `Did the Atlantic close and then re-open?’. This led to the `Wilson Cycle’ concept in which the repeated opening and closing of ocean basins along old orogenic belts is a key process in the assembly and breakup of supercontinents. The Wilson Cycle underlies much of what we know about the geological evolution of the Earth and its lithosphere, and will no doubt continue to be developed as we gain more understanding of the physical processes that control mantle convection, plate tectonics, and as more data become available from currently less accessible regions. This volume includes both thematic and review papers covering various aspects of the Wilson Cycle concept. Thematic sections include: (1) the Classic Wilson v. Supercontinent Cycles, (2) Mantle Dynamics in the Wilson Cycle, (3) Tectonic Inheritance in the Lithosphere, (4) Revisiting Tuzo’s question on the Atlantic, (5) Opening and Closing of Oceans, and (6) Cratonic Basins and their place in the Wilson Cycle.

To this day, there is a great amount of controversy about where, when and how the so-called supercontinents--Pangea, Godwana, Rodinia, and Columbia--were made and broken. Continents and Supercontinents frames that controversy by giving all the necessary background on how continental crust is formed, modified, and destroyed, and what forces move plates. It also discusses how these processes affect the composition of seawater, climate, and the evolution of life. Rogers and Santosh begin with a survey of plate tectonics, and go on to describe the composition, production, and destruction of continental and oceanic crust, and show that cratons or assemblies of cratons became the first true continents, approximately one billion years after the earliest continental crust evolved. The middle part of the book concentrates on supercontinents, beginning with a discussion of types of orogenic belts, distinguishing those that formed by closure of an ocean basin within the belt and those that formed by intracontinental deformation caused by stresses generated elsewhere. This information permits discrimination between models of supercontinent formation by accretion of numerous small terranes and by reorganization of large old continental blocks. This background leads to a description of the assembly and fragmentation of supercontinents throughout earth history. The record is most difficult to interpret for the oldest supercontinent, Columbia, and also controversial for Rodinia, the next youngest supercontinent. The configurations and pattern of breakup of Gondwana and Pangea are well known, but some aspects of their assembly are unclear. The book also briefly describes the histories of continents after the breakup of Pangea, and discusses how changes in the composition of seawater, climate, and life may have been affected by the sizes and locations of continents and supercontinents.

The Nemegosenda Lake alkalic rock complex is located about 30 km northeast of Chapleau. The complex consists of arcuate rings and partial rings of gabbro, ijolite, fenite, nepheline syenite, carbonatite, malignite, syenite, and mafic syenite. The intrusion has been cut by numerous alkalic dike rocks. The complex was prospected by Gulf Minerals Canada Limited (formerly Dominion Gulf Company) between 1954 and 1959 and a large tonnage of niobium mineralization was discovered. The complex was revisited to collect samples for thin section examination and chemical analysis. The complex had been previously mapped.

The present volume is the result of activities within the scientific programme "Response of the Earth System to Impact Processes" (IMP ACT) of the European Science Foundation (ESF). The ESF is an association of 67 national member organisations devoted to scientific research in 24 European countries. The IMPACT programme is aimed at understanding meteorite impact processes and their effects on the Earth System. Launched in 1998 for a duration of 5 years, the programme is now supported by 15 ESF membership countries. The programme of meteorite impact research and operates through deals with all aspects workshops, exchange programs, and short courses. The 4th IMPACT programme workshop "Meteorite Impacts in Precambrian Shields" took place on May 24-28, 2000, in Lappajarvi, western Finland. A total of 84 scientists from 19 countries from Europe, North America, and Africa participated in the workshop. During the workshop, 43 oral, 31 poster, and several video presentations were made. An exhibition of impactite rocks from Finnish craters and two excursions were organised. The excursion to impact melt rock outcrops of the Lappajarvi structure took place during the workshop. The Karikkoselka and Saaksjarvi impact structures in south-central Finland were visited during the post-meeting excursion.

Volume 26 of Reviews in Mineralogy provides a multidisciplinary review of our current knowledge of contact metamorphism. As in any field of endeavor, we are provided with new questions, thereby dictating future directions of study. Hopefully, this volume will provide inspiration and direction for future research on contact metamorphism. The Mineralogical Society of America sponsored the short course on Contact Metamorphism, October 17-19, 1991, at the Pala Mesa Resort, Fallbrook, California, prior to its annual meeting with the Geological Society of America.

Petrology and Genesis of Igneous Rocks comprises of two parts - the first part (Chapters 1 to 8) deals with constituent minerals, texture, thermodynamic principles, phase relations in natural rock systems and causes of diversity in a single petrographic province. Petrology of the crust, mantle and core, the convective cycle patterns in the mantle and their relation to magma genesis and physicochemical properties of magma are also discussed in this part. Use of Isotope geology in determination of age and degree of magma mixing is included towards the end of the first part. The second part (Chapters 9-13) describes individual rock types, from various countries including their geochemistry, petrology and genesis.