The sub-vertical meso-and micro-structures and fabrics developed in coesite-bearing foliated eclogites in the Taohang (桃行) area,southeastern Shandong (山东),China. The diagnostic structures and fabrics,including penetrative foliation or mylonitic foliation containing mineral and stretching lineations,as well as sheath-like folds,appear to be the development of anastomosing UHP eclogite-facies shear belt arrays hosting massive eclogites. Textural relationships and mineral assem-blages indicate that the deformation of foliated eclogites developed closely after the formation of the massive eclogite,prior to the development of the granulite/amphibolite-facies symplectites and coronas,occurring over a very wide pressure range of (31-8)×102 MPa. It presents the structural records of the tectonometamorphic processes as being responsible for the earliest stages of exhumation of the UHP metamorphic rocks. Extensive regional field observations show that the meso-and micro-structures and fabrics recognized in the foliated eclogites at Taohang are remarkably similar or consistent in the whole Dabie (大别)-Sulu (苏鲁) UHP metamorphic belt. This article,thus,supports the idea that the earliest stages of exhumation of the UHP metamorphic rocks,from mantle depths to the Moho or the mantle-crust boundary layering,may be attributed mainly to a sub-vertical extrusion and ductile flow along the subduction channel,belonging to a syn-collision exhumation at about 235 to 220 Ma.
Different scales of structural data reveal a complex deformation history of ultrahigh- pressure (UHP) rocks exposed in the Weihai-Rongcheng area, NE Sulu (northern Jiangsu-eastern Shandong), eastern China. Excluding pre-UHP deformations, at least five major sequential deformational stages (D1–D5) are recognized. The first deformation (D1) produced a weak foliation and lineation in massive eclogites. The foliated eclogite with a dominant foliation containing a stretching and mineral lineation was developed during the D2 deformation. Both the D1 and D2 deformations occurred under UHP metamorphic conditions, and are well preserved in the eclogite bodies. D3 structures which developed shortly after the formation of granulite/amphibolite facies symplectites are characterized by imbricated associations marked by a regional, steeply dipping foliation, compositional layering, eclogite boudinage, isoclinal folds and reverse ductile shear zones. The D3 deformation was accompanied by decompressional partial melting. A regional, gently dipping amphibolite facies foliation and stretching lineation, low-angle detachments, and dome- and arc-shaped structures formed during the D4 deformation stage dominate to some degree the map pattern of the Weihai-Rongcheng UHP domain. The last stage of deformation (D5) gave rise to the final exhumation of the UHP rocks. D5 is characterized by development of brittle-dominated high-angle faulting associated with emplacement of large volumes of undeformed granite plutons and dykes dated at 134–100 Ma. The deformational and metamorphic sequence followed by the UHP rocks in the Weihai-Rongcheng area is similar to that studied in the entire Dabie-Sulu UHP and HP metamorphic belts from microscopic to mapping scale. Based on structural data, combined with available petrographic, metamorphic and geochronological data, a speculative tectonic evolutionary model for the Dabie-Sulu UHP and HP belts is proposed, involving continental subduction/collision between the Sino-Korean and Yangtze cratons and
