Further evidence for 1.85 Ga metamorphism in the Central Zone of the North China Craton: SHRIMP U-Pb dating of zircon from metamorphic rocks in the Lushan area, Henan Province

摘要

This paper reports SHRIMP zircon U-Pb dating of Precambrian supracrustal and granitic rocks from the Lushan area, Henan Province, in the southern portion of the Central Zone (also referred to as the Trans-North China Orogen) of the North China Craton. A graphite-garnet-sillimanite gneiss (Sample TW0006/1) of the Shangtaihua 'Group' gives a range of inherited zircon ages from 2.73 to 2.26 Ga and a metamorphic zircon age of 1.84 +/- 0.07 Ga. A gamet-bearing gneissic granitoid (Sample TWJ358/1), which is considered to intrude the Shangtaihua 'Group', gives a magmatic zircon age of 2.14 +/- 0.02 Ga and a metamorphic zircon age of similar to 1.87 Ga. The metamorphic zircon ages of 1.87-1.84 Ga obtained in this study indicate that an important tectonothermal event occurred at the end of the Paleoproterozoic in the Lushan area. This supports the southern continuation of a Central Zone in the North China Craton that workers have recently considered to result from continent-continent collision. It is also evident that the Shangtaihua 'Group' was formed during the Paleoproterozoic (between 2.26 and 2.14 Ga), and not during the Archean, as previously considered. (c) 2005 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.