Ophiolites and other mafic-ultramafic complexes in Alaska
Mafic and ultramafic complexes are widespread throughout Alaska, ranging in size from huge allochthonous masses several hundred square kilometers in area to tiny isolated blocks (Fig. 1). Some of these, such as the complexes in northern and western Alaska, clearly can be labeled ophiolites; others, such as the concentrically zoned bodies of southeastern Alaska, are not ophiolites; and still others, such as those in the Livengood belt of central Alaska, have uncertain affinities. All of the complexes discussed here, however, belong to well-defined belts that for the most part are confined to specific lithotectonic terranes or lie along terrane boundaries. Few of these complexes have been studied in detail, and the mode and time of emplacement of most are uncertain or controversial. In this chapter, we review available information on the structural setting and petrography of the complexes, and we describe the tectonic models that have been suggested to explain the mode of emplacement.
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You get a comprehensive overview of the geology, tectonic evolution, and mineral resources of Alaska and adjacent areas of the continental margin. Plates include state-wide maps showing geology, physiography, lithotectonic terranes, metamorphic rocks, igneous rocks, sedimentary basins, isotopic age data, neotectonics, isostatic gravity, magnetics, and metallic mineral deposits. Summaries of bedrock geology and geologic history are given for eleven large regions of Alaska and adjacent offshore areas. Twenty topical chapters synthesize data on metamorphic and igneous rocks; major onshore and offshore sedimentary basins; the paleomagnetics evidence for latitudinal displacements and rotations, glacial history and periglacial phenomena; and the occurrence, evolution, and potential of Alaska's vast resources of petroleum, coal, and metallic minerals. A summary chapter provides an overview and presents a possible model for Alaska's Phanerozoic evolution. The Geology of Alaska is the largest publication produced in the Decade of North American Geology program, a fitting tribute to this magnificent area.