Tectonic evolution of a greenstone sequence in northern Zimbabwe: sequential early stacking and pluton diapirism

Structural-metamorphic relationships in the 2.71-2.64 Ga Harare-Shamva gree nstone belt in northern Zimbabwe demonstrate that the Archean stratigraphy of the Zimbabwe craton can not be regarded as a coherent and nonrepetitive, autochthonous succession of (ultra)mafic and felsic greenstones. The green stone belt shows an early set of amphibolite-grade D-1/M-1 structures and a ssociated synkinematic metamorphic assemblages that were formed during an e pisode of layer-parallel shearing at about 2.64 Ga. This resulted in sequen tial west directed imbricate stacking and recumbent folding of distinct tec tonostratigraphic greenstone sequences and includes the development of a sy ntectonic sedimentary succession. D-2/M-2 fabrics, strain patterns, and con tact aureoles overprint D-1 geometries and are related to the diapiric empl acement of the Chinamora batholith. The structural data indicate that grani te-gneiss terrains can be subdivided into two types: (1) structurally empla ced terrains (the Madziwa gneiss terrain) and (2) diapiric domes (the China mora batholith). The history of the Harare-Shamva greenstone belt indicates that the late Archean (2.7-2.6 Ga) evolution of the Zimbabwe craton must a llow for accretion of diverse crustal fragments including oceanic and back are mafic crust, volcanic are felsic crust, continental crust, and related sedimentary sequences. The process of accretion was probably diachronous ac ross the craton and may have involved concomitant diapirism, strike-slip fa ulting, magma intrusion, and sedimentation.