ON DYNAMIC SELF-ORGANIZATION: EXAMPLES FROM MAGMATIC AND OTHER GEOCHEMICAL SYSTEMS

Abstract

STANDARD LIESEGANG BANDING IS THE DISPLAY OF PARALLEL BANDS OF PRECIPITATE FORMED PERIODICALLY WHEN CO-PRECIPITATE IONS INTERDIFFUSE IN A GEL MEDIUM. THE MOST STRIKING RESEMBLANCE WITH LIESEGANG PATTERNS IN NATURE LIES IN THE DIVERSE SCENERY OF BANDED TEXTURAL FEATURES COMMONLY OBSERVED IN SOME GEOLOGICAL MATERIALS, SUCH AS GEODES, AGATES, MALACHITES, AS WELL AS STRATIGRAPHIC UNITS OF CERTAIN ROCK FORMATIONS. HERE, WE EXPLORE THE POSSIBLE RELATIONSHIP BETWEEN THE LIESEGANG BANDING SCENARIO AND MAGMATIC-TYPE PATTERN FORMATION, SUCH AS ZONATIONS IN KM-SCALE CIRCULAR ZONED PLUTONS AND ANOROGENIC RING COMPLEXES, CYCLIC LAYERING IN LARGE MAFIC–ULTRAMAFIC LAYERED INTRUSIONS AND ORBICULAR GRANITES, AS WELL AS IN MM-SCALE CRYSTAL ZONATIONS. WE ALSO INVESTIGATE MAGMATIC PROCESSES SUCH AS FRACTIONAL CRYSTALLIZATION, AND THE RANGES OF T AND P THAT ARE COMPATIBLE WITH OPERATING CONDITIONS FOR LIESEGANG BANDING. FOR GEOCHEMICAL SELF-ORGANIZATION TO OPERATE VIA A LIESEGANG-TYPE MECHANISM, A NECESSARY CONDITION IS THAT THE SYSTEM BE TRANSIENTLY OUT OF EQUILIBRIUM, AND BE DESCRIBED BY COMPLEX NONLINEAR KINETIC LAWS. WE EXAMINE THE VIABILITY OF THE DEVELOPMENT OF GEOCHEMICAL PATTERNS, IN RELATION WITH THE VARIOUS REQUIREMENTS FOR THE GROWTH OF LIESEGANG STRUCTURES.