weight: bold" lang=EN-US>Characteristics of Tectogenetic Banded Ironstones in Greenstone Belts, Zimbabwe, Henan Province
摘要
Widespread banded ironstones in Zimbabwe constitute a common lithologic unit in the stratigraphic sequence of greenstone belts of the Archaean Zimbabwe craton. Lithologically, the banded ironstones are similar to “sulphide-facies” banded iron formations, but they actually belong to silicified and sulphide-mineralized shear zones. Formerly, these tectogenetic banded ironstones were regarded as original sedimentary rock formations, but on outcrops in the field they can be distinctly recognized by anastomosing schistosity bands, fold deformation bands, ptymatic structures and mylonitized bands distributed along the ironstone beds. On a regional scale the ironstone beds intersect schistosity and bedding of rock formations with an anastomosing distribution, and the same lithologic unit may repeatedly appear. Before deformation of rock formations resulted from diapiric rise of granites, a series of thrust faults caused the primary volcano-sedimentary lithologic units to be horizontally extended, imbricated, thrusted?? and repeatedly appeared. Consequently, these “iron-filling cakelike type” rock formations of tectogenetic banded ironstones contained in the stratigraphic sequence of greenstone belts have become an increasingly important research focus for geologists.