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Polyphase deformation of the Weihai-Rongcheng UHP Unit Rocks,NE Sulu:Insights into the Tectonic Evolution of the Dabie-Sulu UHP and HP Belts,China

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Acta Geologica Sinica(English Edition) 2007年第1期81卷 42-54页

作者： SUO Shutian ZHONG Zengqiu ZHOU Hanwen YOU Zhendong Faculty of Earth Sciences China University ofGeosciences Wuhan Hubei 430074 State Key Laboratory of Geo-Processes and Mineral Resources China University of Geosciences Wuhan Hubei 430074 School of Earth Science and Mineral Resources China University of Geosciences Beijing 100083

Different scales of structural data reveal a complex deformation history of ultrahigh- pressure （UHP） rocks exposed in the Weihai-Rongcbeng area, NE Sulu （northern Jiangsu-eastern Shandong）, eastern China. Excluding pre-UHP deformations, at least five major sequential deformational stages （D1-Ds） are recognized. The first deformation （DO 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 I）2 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-Rongcbeng UHP domain. The last stage of deformation （Ds） gave rise to the final exhumation of the UHP rocks. Ds is characterized by development of brittle-dominated high-angle faulting associated with emplacement of large volmnes 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 IIP belts is proposed, involving continental subduction/collision be

关键词： Weihai-Rongcheng area ultrahigh-pressure (UHP) metamorphism tectonic evolution,polyphase deformation deformation partitioning

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On the material invariant of 110°-conjugate angle of shear bands——Reply to Gomez-Rivas and Griera(2015)

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Science China Earth Sciences 2015年第12期58卷 2363-2368,1-3页

作者： ZHENG YaDong ZHANG JinJiang WANG Tao The Key Laboratory of Orogenic Belts and Crustal Evolution Ministry of Education School of Earth and Space SciencesPeking University Institute of Geology Chinese Academy of Geological Sciences

After their experimental data were re-explained in terms of the maximum-effective-moment （MEM） criterion, Gomez-Rivas and Griera （2015） challenge the validity of the MEM-Criterion in terms of shear fractures, which have mixed up with shear fractures and shear bands. The two features are similar in appearance but different in deformation mechanism （s）. The MEM-criterion proves that ±55° to σ1era are the maximum effective moment directions and the shear bands that formed by mate- rial-line （beddings or fabrics） rotation mechanism have a constant conjugate angle of 110°. Theoretically, the 55° or 110° is a material-invariant, and practically, a statistic-invariant or preferred direction with average deviation of -10°. By this angle, shear bands can be easily recognized from shear fractures with conjugate angle never over 90°. The High-strain deformation in the lozenges usually predates the surrounding shear bands. Two stress states can not coexisted simultaneously in the same place and the resolving cr1＇ normal to the related shear zone represents 0-100% deformation partitioning, depending on the original kinematic vorticity of the shear zones.

关键词： kink-bands/shear bands deformation localization MEM-criterion deformation partitioning

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Using the Maximum Effective Moment Criterion to Interpret Quartz -Fabric Patterns

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Acta Geologica Sinica(English Edition) 2019年第4期93卷 799-809页

作者： ZHENG Yadong ZHANG Jinjiang ZHANG Bo The Key Laboratory of Orogenic Belts and Crustal Evolution School of Earth and Space SciencesPeking UniversityBeijing 100871China

The Maximum Effective Moment(MEM)criterion predicts that the initial orientation of ductile shear zones and shear bands is^55°relative to the maximum principal stress axis(σ1)and that the kinematic vorticity number(Wk)is^*** preferred orientations should be reflected in the pattern of quartz-fabrics in shear zones and shear *** quartz-fabrics in plane strain can be divided into low-temperature(L)and high-temperature(H)fabrics,with each group showing three patterns.A steady flow with a constant value of Wk≈0.94 gives rise to L-1 and H-1 patterns,which are commonly characterized by a singleaxis girdle normal to the shear zone and a single-point maximum parallel to the shear *** the conjugate set develops,L-1 and H-1 have opening angles of^70°and^110°,respectively.L-2 and H-2 are asymmetric patterns associated with variable deformation partitioning and vorticity values of0deformation partitioning and Wk=*** opening angle in quartz-fabrics is implicitly linked to the temperature during *** opening angle is^70°at low temperature and^110°at high ***,a linear correction between the opening angle and the temperature cannot be *** deformation partitioning,synthetic shear bands form earlier than antithetic bands and are more easily *** may result in opening angles of110°for high-temperature *** following criteria can be used to recognize reworked shear zones that have experienced multiple orogenic phases and changes in the stress state:1)the initial Wk is larger or smaller than^0.94;2)the change in Wk is abrupt,rather than progressive;3)inconsistent shear senses are inferred for the different phases of deformation;and4)a negative value of Wk is found in reworked shear zones.

关键词： deformation localization deformation partitioning shear bands vorticity Wk quartz CPO patterns

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