Ž . Chemical Geology 157 1999 119–146 Crust–mantle interaction induced by deep subduction of the continental crust: geochemical and Sr–Nd isotopic evidence from post-collisional mafic–ultramafic intrusions of the northern Dabie complex, central China Bor-ming Jahn a, ) , Fuyuan Wu a,b , Ching-Hua Lo c , Chin-Ho Tsai d a Geosciences Rennes, UniÕersite de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France ´ ´ b Department of Geology, Changchun UniÕersity of Earth Sciences, Changchun 130061, China c Department of Geology, National Taiwan UniÕersity, 245 Choushan Rd., Taipei 10770, Taiwan d Department of Geological and EnÕironmental Sciences, Stanford UniÕersity, Stanford, CA 94305, USA Received 20 May 1998; revised 2 December 1998; accepted 2 December 1998 Abstract Interaction of deeply subducted continental blocks with the upper mantle peridotite is a likely process, but it has never been demonstrated. New geochemical and isotope tracer analyses of post-collisional mafic–ultramafic rocks from the Dabie terrane in central China show that they could have been generated by melting of such metasomatized mantle as a result of Ž . crust–mantle interaction. Isotopic dating using different techniques Rb–Sr, Sm–Nd and Ar–Ar has established that these Ž . mafic–ultramafic rocks were emplaced post-tectonically in early Cretaceous f120–130 Ma , nearly contemporaneous with the massive intrusions of granitic plutons. They did not form as part of the early Paleozoic arc complex, nor did they Ž . undergo UHP metamorphism at about 220 Ma. The strong enrichment of light rare earth elements REE and the highly Ž . Ž . negative ´ T values about y15 to y20 for all mafic and ultramafic rocks indicate their derivation from an enriched Nd mantle source. Significant negative Nb anomalies observed in the spidergrams and other ‘crustal’ signatures of these rocks suggest an important role of continental material in their petrogenesis. We interpret that the singular geochemical and Ž . isotopic characteristics witness a post-collisional interaction between the subducted ancient crust Yangtze craton and the Ž . mantle peridotite asthenosphere . Partial melting of such metasomatized mantle produced the basic magmas, in response to the same thermal pulse that was responsible for the massive Cretaceous granitic intrusions and resetting of some isotopic clocks in UHP metamorphic rocks. Taking into consideration all geochemical and isotopic constraints, a tectonic model is presented with emphasis on the post-collisional crust–mantle interaction and possible heat sources required for massive Cretaceous granitic intrusions. We also advocate that the digestion of deeply subducted continental blocks in the upper mantle may represent an efficient way of crustal recycling when dealing with the problem of continental growth and destruction. q 1999 Elsevier Science B.V. All rights reserved. Keywords: Dabie terrane; UHP terrane; Continental subduction; Mafic–ultramafic intrusion; Crust–mantle interaction; Age dating; Sr–Nd isotopes ) Corresponding author. Tel.: q33-99-28-60-83; fax: q33-299-28-67-72; e-mail: jahn@univ-rennes1.fr 0009-2541r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. Ž . PII: S0009-2541 98 00197-1