LATE- TO POST-TECTONIC SETTING OF SOME MAJOR PROTEROZOIC ANORTHOSITE – MANGERITE – CHARNOCKITE – GRANITE (AMCG) SUITES

摘要: Recent zircon-based geochronological investigations in the Adirondack Mountains, state of New York, demonstrate that 1155 ± 6 Ma massif anorthosite was emplaced during post-contractional phase (1160–1140 Ma) ca. 1200–1140 Shawinigan orogeny. Emplacement many other – mangerite charnockite granite (AMCG) suites also correlates with waning stage orogeny and includes Morin Lac-Saint-Jean complexes, 1650 Mealy Mountain complex, 1450 complexes eastern Labrador. The correlation applies to 930 Rogaland complex Norway 1060–1020 late- post-Ottawan anorthosites central Quebec Appalachians Virginia southeastern Pennsylvania. These correlations suggest models involving delamination overthickened orogenic lithosphere by foundering or convective removal, followed asthenospheric ascent, ponding gabbroic melt at crust–mantle interface. Orogen rebound following results stable, dynamically balanced settings which magma evolves slowly high pressure produce high-aluminum pyroxene coarse, intermediate plagioclase characteristic anorthosite. Related melting lower crust produces mangeritic charnockitic magma. Ultimately, both anorthositic granitic magmas ascend, lower-pressure fractionation yields classic AMCG suites. Transtensional reactivation lithospheric-scale shear zones old sutures important magmatism provides conduits for ponds interface deep Flat-slab subduction, back-arc extension, slab breakoff, hotspots represent alternative can account underplating resulting suites, if consistent constraints.