Quantitative structural analyses and numerical modelling of ...

More documents

Recommendations

Info

5 - 10 LEXA ET AL.: COLLISION IN WEST CARPATHIANSFigure 6. Schematic block diagrams showing tectonic evolution of the studied area. (a) Development ofthe Gemer Cleavage Fan due to indentation of sub-Gemer basement. (b) Development of the Trans-Gemer Shear Zone and Eastern Gemer Thrust Zone resulting from interaction between the Veporpromontories with sub-Gemer basement.foliation of the EGT system are dipping to the SW, bear anintense stretching lineation plunging to the SW and show atop-to-the-NE sense of shearing.4. Tectonic Model of Cretaceous Collision[30] The structural pattern and succession of deformationstructures described above allow modeling of the tectonicevolution of SW Carpathians and development of polyphasecleavage patterns. Our interpretation is based on mutualstrength relationships between individual units at the onsetof Cretaceous convergence. Cretaceous tectonics of theWest Carpathians is characterized by north vergent collisionof a southern continent with the northerly lying WestCarpathian domain (European plate). Fragments of thesouthern continental domain, now located in northern Hungary(Bükk mountains), are considered to be Neo-Proterozoicin age [Pantó et al., 1967]. Here, the absence ofVariscan overprint is manifested by continuous sedimentationfrom the Early to Late Paleozoic. We suggest that thissouthern continent behaved as a rigid indenter controllingthe deformation of all northerly foreland crustal units, and inour coordinate system was actively moving toward thenorth. The mechanical contrast between the Vepor basementpromontories and the Gemer slates results from their contrastinglithologies and pre-Cretaceous evolution. Theinterval of thermal relaxation of the Vepor quartzofeldspathiccrust between the last (Late Carboniferous) importantthermal perturbation and Cretaceous collisioncorresponds to about 180 Ma. This indicates, that thegeotherm of the Vepor crust was equilibrated at the onsetof Cretaceous orogeny [Cloetingh and Burov, 1996; Morganand Ramberg, 1987]. Therefore we suggest that the VariscanVepor basement, composed of gneisses and granites, representeda mechanically strong promontory of irregular shape.In contrast, the Gemer Unit is represented mainly by lowgradeslates composed of fine-grained hydrous mineralswith rheology controlled by diffusion type of deformationmechanisms as pressure solution and diffusive mass transfer[Knipe, 1979, 1989]. For the same geotherm, as comparedwith laterally adjacent quartzofeldspathic rocks, the strengthof Gemer slates was incomparably lower. Taking intoaccount these rheological assumptions, the Gemer Unitduring the Cretaceous event is considered to be the weakestdomain accommodating most of the viscous deformation.[31] In agreement with Woodcock et al. [1988] andSintubin [1999], the cleavage patterns in deformable weakrocks reflect the geometry and direction of movement ofrigid blocks. In order to model the development of superposedcleavage pattern described above, it is important todefine boundary conditions.4.1. Definition of Kinematic Frame[32] The asymmetry of the GCF can be interpreted as aresult of movement of rigid indenting block to the north andback thrusting of metasediments over its northern margin.The rigid basement does not crop out, but it can be traced indeep seismic lines 2T and G1 [Tomek, 1993; Vozár andŠantavý, 1999; Vozár et al., 1996]. The seismic profilingshows that the Gemer Unit is about 5 km thick sheet-likebody resting on a basement of unknown age. This majorlithological boundary is represented by series of stronghorizontal reflectors. The most spectacular structure inseismic line G1 [Vozár and Šantavý, 1999; Vozár et al.,1996] is a highly reflective south dipping zone along whichthe horizontal base of the Gemer Unit is displaced to thenorth. This zone is interpreted as the major Sub-Gemerthrust fault responsible for northward thrusting of rigidbasement over weak sediments resulting in the developmentof GCF (Figure 6).[33] Important question in our model is the displacementof Vepor basement rocks with respect to the Gemer Unit. Itis well known that the whole central and southern Carpathiandomain was actively moving to the north (in recentcoordinates) as documented by Cretaceous progressiveclosure of Mesozoic Fatric basinal domain north of theVepor basement [Plašienka, 1997]. In this kinematic frameall units are shifted to the north but only differential move-94
LEXA ET AL.: COLLISION IN WEST CARPATHIANS 5 - 11Figure 7. (a) Initial geometry and boundary conditions of the numerical model. The arrow indicates thevelocity and trajectory of the indenter northern margin, with v = 0; zero Dirichlet boundary condition forvelocity; outflow, zero Neumann boundary condition for velocity. (b) Finite strain pattern developed inweak zone after 1 Myr of shortening. Distribution of strain intensity expressed in D value and orientationpattern of XY plane of finite strain ellipsoid. The foliations trajectories are shown by lines and theorientation of lineation is expressed by the color of foliation trace. White line corresponds to horizontallineation and black line to vertical one. (c) Finite strain pattern developed in weak zone after 3 Myr ofshortening. Distribution of strain intensity expressed in D value and orientation pattern of XY plane offinite strain ellipsoid. (d) Distribution of finite strain symmetry expressed in K value.ments within the Vepor-Gemer system are responsible for itsinternal deformation. Important observation is that thedeformation intensity in central part of the Gemer Unitvanishes to the north. In this area, the Vepor basement ispresent (covered by Tertiary sediments) but no increase inCretaceous deformation intensity has been observed. Thismeans that this Vepor segment does not creating importantdeformation resulting from possible movement to the south.Therefore we suggest that the Vepor promontories did notmove actively to the south, and extreme deformation alongwestern and eastern Vepor promontories was imposed bygenerally northward flow of weak material. In conclusion,the only differentially moving rigid block is the northwardthrusted part of sub-Gemer basement. All other basementunits can be further considered kinematically fixed.[34] Our field studies showed that apart from GCF, anintense deformation was concentrated along southeasternedge of the western Vepor promontory producing TGSZ andalso along southwestern edge of the eastern Vepor promontoryresponsible for the origin of EGT (Figure 6b). Thedevelopment of TGSZ probably results from a major changein mutual translation direction of southern sub-Gemer blockand western Vepor promontory due to their oblique collisionat deeper crustal levels. Localized transpressional deformationin upper crustal levels is a typical expression of obliqueconvergence in many active regions, e.g., San Andreas faultzone [Teyssier and Tikoff, 1997], Sumatra [Tikoff andTeyssier, 1994], or Alpine fault in New Zealand [Teyssieret al., 1995].4.2. Numerical Modeling of ProgressiveDeformation of the Gemer Unit[35] The presented numerical approach enables to modelthe deformation in a weak zone surrounded by rigid blocksor free boundaries. The approach is based on the thinviscous sheet approximation being similar to that one usedby England et al. [1985] for modeling the deformation ofthe whole lithosphere. We assume a horizontal weak tabulardomain to have been subjected to flow with no tractions attop and bottom surface. We consider vertical gradients ofthe horizontal velocity to be negligible, which allows us tointegrate the equations of motion over the vertical dimensionand to work with vertical averages of stress and strainrates. When linear constitutive relation between stress andstrain rates is considered, the procedure leads to a system ofelliptic partial differential equations for two horizontalvelocity components (see Appendix A). The system issolved by the finite element method, with the Dirichletand Neumann boundary conditions applied to segments ofthe domain boundaries corresponding to the describedgeological settings (rigid indenter, free inflow or outflow95
Page 3:
“It strikes me that all our knowl
Page 8 and 9:
Contentsviii4.7 Schulmann, Konopás
Page 11:
Dedicated to my wife Markéta, daug
Page 14 and 15:
Foreword 2First topic “Quantitati
Page 16 and 17:
Foreword 4source and freely availab
Page 18 and 19:
1. Quantitative analysis of deforma
Page 20 and 21:
Page 22 and 23:
Page 24 and 25:
Page 26 and 27:
Page 28 and 29:
Page 31 and 32:
Chapter 2Mechanisms of lower crusta
Page 33 and 34:
2. Mechanisms of lower crustal flow
Page 35 and 36:
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Chapter 3Quantitative analyses ofme
Page 43 and 44:
3. Quantitative analyses of metamor
Page 45 and 46:
Page 47 and 48:
Page 49 and 50:
Page 51:
Page 54 and 55:
Bibliography 42Culshaw, N., Beaumon
Page 56 and 57: Bibliography 44sources and trigger
Page 58 and 59: Bibliography 46Skrzypek, E., Štíp
Page 61 and 62: Journal of Structural Geology 23 20
Page 63 and 64: J. KonopaÂsek et al. / Journal of
Page 81 and 82: JOURNAL OF GEOPHYSICAL RESEARCH, VO
Page 83 and 84: SCHULMANN ET AL.: STRAIN DISTRIBUTI
Page 95: SCHULMANN ET AL.: STRAIN DISTRIBUTI
Page 98 and 99: 5 - 2 LEXA ET AL.: COLLISION IN WES
Page 108 and 109: 5 - 12 LEXA ET AL.: COLLISION IN WE
Page 114 and 115: 156O. Lexa et al. / Journal of Stru
Page 121 and 122: DTD 5ARTICLE IN PRESSJournal of Str
Page 123 and 124: DTD 5ARTICLE IN PRESSL. Baratoux et
Page 135 and 136: Table 1Statistical values of the qu
Page 141 and 142: Table 2Summary of parameters derive
Page 145 and 146: J. metamorphic Geol., 2008, 26, 273
Page 147 and 148: EXHUMATION IN LARGE HOT OROGEN 275m
Page 149 and 150: Probabi l irequencyProbabi l ireque
Page 151 and 152: EXHUMATION IN LARGE HOT OROGEN 279y
Page 153 and 154: EXHUMATION IN LARGE HOT OROGEN 281N
Page 155 and 156: EXHUMATION IN LARGE HOT OROGEN 283w
Page 157 and 158:
EXHUMATION IN LARGE HOT OROGEN 285a
Page 159 and 160:
EXHUMATION IN LARGE HOT OROGEN 287w
Page 161 and 162:
EXHUMATION IN LARGE HOT OROGEN 289T
Page 163 and 164:
EXHUMATION IN LARGE HOT OROGEN 291O
Page 165 and 166:
EXHUMATION IN LARGE HOT OROGEN 293r
Page 167 and 168:
EXHUMATION IN LARGE HOT OROGEN 295B
Page 169:
EXHUMATION IN LARGE HOT OROGEN 297R
Page 172 and 173:
Author's personal copyK. Schulmann
Page 174 and 175:
Page 176 and 177:
Page 178 and 179:
Page 180 and 181:
Page 182 and 183:
Page 184 and 185:
Page 186 and 187:
Page 188 and 189:
Page 190 and 191:
Page 193 and 194:
J. metamorphic Geol., 2011, 29, 79-
Page 195 and 196:
HEAT SOURCES AND EXHUMATION MECHANI
Page 197 and 198:
Page 199 and 200:
Page 201 and 202:
Page 203 and 204:
Page 205 and 206:
Page 207 and 208:
Page 209 and 210:
Page 211 and 212:
Page 213 and 214:
Page 215 and 216:
Page 217 and 218:
Page 219 and 220:
EXTRUSIONOFLOWERCRUSTINVARISCANOROG
Page 221 and 222:
Page 223 and 224:
Page 225 and 226:
Page 227 and 228:
Page 229 and 230:
Page 231 and 232:
Page 233 and 234:
Page 235 and 236:
Page 237 and 238:
Page 239 and 240:
Page 241 and 242:
Page 243 and 244:
J. metamorphic Geol., 2005, 23, 649
Page 245 and 246:
CONTRASTING TEXTURAL RECORD OF TWO
Page 247 and 248:
Page 249 and 250:
Page 251 and 252:
Page 253 and 254:
Page 255 and 256:
Page 257 and 258:
Page 259 and 260:
Page 261 and 262:
Contrasting microstructures and def
Page 263 and 264:
TEXTURES OF NATURALLY DEFORMED META
Page 265 and 266:
Page 267 and 268:
Page 269 and 270:
Page 271 and 272:
Page 273 and 274:
1.0--0.9__Mg~(Mg2++Fe2+)9 Core of p
Page 275 and 276:
Page 277 and 278:
' ~'-----2~--~----TEXTURES OF NATUR
Page 279 and 280:
Page 281 and 282:
Page 283 and 284:
Page 285 and 286:
Page 287 and 288:
Page 289:
Page 292 and 293:
B10210ZÁVADA ET AL.: EXTREME DUCTI
Page 294 and 295:
Page 296 and 297:
Page 298 and 299:
Page 300 and 301:
Page 302 and 303:
Page 304 and 305:
Page 307 and 308:
ClickHereforFullArticleJOURNAL OF G
Page 309 and 310:
B10406SCHULMANN ET AL.: RHEOLOGY OF
Page 311 and 312:
Page 313 and 314:
Page 315 and 316:
Page 317 and 318:
Page 319 and 320:
Page 321 and 322:
Page 323 and 324:
Page 325 and 326:
Page 327 and 328:
Page 329 and 330:
ORIGIN OF FELSIC MIGMATITES 31Ó 20
Page 331 and 332:
ORIGIN OF FELSIC MIGMATITES 33durin
Page 333 and 334:
ORIGIN OF FELSIC MIGMATITES 35(a)Ty
Page 335 and 336:
ORIGIN OF FELSIC MIGMATITES 37(a)Pl
Page 337 and 338:
ORIGIN OF FELSIC MIGMATITES 39Grain
Page 339 and 340:
ORIGIN OF FELSIC MIGMATITES 41(a)(b
Page 341 and 342:
ORIGIN OF FELSIC MIGMATITES 43(a)(b
Page 343 and 344:
ORIGIN OF FELSIC MIGMATITES 45Fig.
Page 345 and 346:
ORIGIN OF FELSIC MIGMATITES 47produ
Page 347 and 348:
ORIGIN OF FELSIC MIGMATITES 49stron
Page 349 and 350:
ORIGIN OF FELSIC MIGMATITES 51Cmı
Page 351:
ORIGIN OF FELSIC MIGMATITES 53easte
Page 354 and 355:
104 J. FRANĚK ET AL.in terms of th
Page 356 and 357:
106 J. FRANĚK ET AL.Fig. 2. Struct
Page 358 and 359:
108 J. FRANĚK ET AL.(a)perthite po
Page 360 and 361:
110 J. FRANĚK ET AL.(a)(b)(c) (d)
Page 362 and 363:
112 J. FRANĚK ET AL.Table 1. Repre
Page 364 and 365:
114 J. FRANĚK ET AL.at these P-T c
Page 366 and 367:
116 J. FRANĚK ET AL.(a)(b)Fig. 10.
Page 368 and 369:
Page 370 and 371:
120 J. FRANĚK ET AL.Table 2. Quant
Page 372 and 373:
Page 374 and 375:
124 J. FRANĚK ET AL.Fig. 16. Inter
Page 376 and 377:
126 J. FRANĚK ET AL.development of
Page 378 and 379:
128 J. FRANĚK ET AL.Behrmann, J.H.
Page 380:
130 J. FRANĚK ET AL.Southern Bohem
show all

Quantitative structural analyses and numerical modelling of ...

Create successful ePaper yourself

Delete template?

Save as template?