Micro‐sampling Lu–Hf geochronology reveals episodic garnet growth and multiple high‐P metamorphic events

• DOI: 10.1111/jmg.12185
• Publication Date: 2016-02-05T20:39:54Z
• Authors: H. Cheng; X. C. Liu; J. D. Vervoort; D. Wilford; D. D. Cao
• Keywords: Geochronology

Abstract We present Lu–Hf dates from multiple growth zones within two large garnet porphyroblasts by a micro‐sampling method. A single eclogite sample, taken the Huwan shear zone in Hong'an orogen, was investigated with geochronology and traditional bulk separation methods. The sample contains few up to several centimetres diameter second major population of smaller (0.1–2.0 mm) porphyroblasts, comprised dark cores pale rims. Elemental compositions mineral inclusions appear consistent generations. ( c . 400–264 Ma) were determined twelve micro‐sawed sections porphyroblasts. These overlap age peaks defined 115 SIMS zircon U–Pb analyses same sample. Bulk separates define minimum date 306 Ma maximum 252 for rims respectively. interpreted bracket period broad interval 400 264 is best explained protracted episodic growth, which may require that these rocks experienced subduction cycles initiated during Devonian terminated Triassic.