1974/01/01 by Keith A. W. Crook, Keith A.W. Crook
Earth and Planetary Sciences · #Geological and Geochemical Analysis #Geological and Geophysical Studies #Geological Studies and Exploration
paper · doi:10.1086/627934
West Pacific-type geosynclines are represented by the modern island arc, microcontinent, and marginal sea terranee of the West and Southwest Pacific, the Caribbean and Central America, and the Scotia Sea. Ancient examples include the Tasman Geosyncline, the Paleozoic geosyncline in eastern Kazakhstan and the northern Tien-Shan, and parts of the Archean kratonic nucleii. West Pacific-type geosynclines are particularly productive "machines" that convert oceanic into continental crust by a process termed "kratonization." They produce perhaps an order of magnitude greater lateral growth of continents than do Atlantic-type geosynclines during a comparable time interval. To assist in analyzing the kratonization process, a succession of kratonization stages is recognized on the basis of studies in part of the Tasman Geosyncline. These stages depend for their recognition upon the diverse modes of occurrence of quartz in the geosynclinal rock pile. The stages, each marked by appreciable quantities of quartz in a previously unrepresented mode of occurrence, are: (1) quartz in chert; (2) quartz in veins; (3) detrital quartz in arenites; (4) quartz in granitic rocks; (5) quartz in volcanic and volcaniclastic rocks; (6) detrital quartz in intramontane sediments; (7) quartz in platform sediments; (8) pedogenic quartz in silcrete. The pattern of kratonization thus revealed in the Tasman Geosyncline is depicted by maps and a schematic time-distance diagram. The pattern resembles one derived in a different way for the Paleozoic geosyncline in central Asia. Both show kratonization proceeding outward from the adjoining kraton with time, in contrast to the typical kratonward-directed pattern of Atlantic-type geosynclines.