Index

Page numbers in italics refer to fi gures; those in bold to tables

Acasta gneisses 347 sea fl oor divided into 84 diversity of 288–9 accretionary orogens, structure 287, 309, Aleutian accretionary prism growth latest phase of compression 289 336–42 rate 267 Andean foreland, styles of tectonic active, seismic refl ection profi les 295, 315, Aleutian arc, focal mechanism solutions of shortening 292, 292, 293, 294 340, 342 earthquakes 256, 257 foreland basement thrusts 292, 293 Canadian Cordillera 336–7, 338, 339, 341, Aleutian–Alaska arc, prominent gap in segmentation of foreland 292, 294 376 seismicity 259, 261 thick-skinned and thin-skinned fold and common features of 338, 340, 502 alkaline series, includes shoshonitic thrust belts 292, 293 western North America 336, 337 lavas 271 Andean-type subduction, specifi c types of accretionary prisms 251, 264–9, 270 Alpine Fault, New Zealand 228–30, 338 deposit 417–18 accumulation of sediments including accommodation of oblique slip 244, 245, backarc environment, granite belts with olistostromes 267 246 tin and tungsten 417–18 creation of mélange 268 Breaksea Basin once continuous with stratabound copper sulfi des 417 décollement 264, 266 Dagg Basin 220, 221, 222 Andes, central 301–2 sliding on 267 central segment, weakly/non-partitioned arcuate shape (orocline) 294 deformation front 264 style of transpressional evolution of shortening (model) 300 development of 243, 244 deformation 213, 223 fl at and steep subduction zones 289, 291 and development of forearc basin 267 change in relative plate motion, oblique Neogene volcanism above steeply fold and thrust belt 264 continent–continent collision 228 dipping slab 289 frontal accretion 265 crustal structure below 213, 242, 242 rotation round vertical axis during the large negative anomalies 252 dextral movement, accommodation Neogene 294 lateral growth 265–6 of 213, 220, 228 seismic refl ection profi le suggests long-term circulation of material in 267 dextral transform fault 113, 113 presence of fl uids 274–5, 296 Nankai Trough 264, 266 Five Fingers Basin 220, 221 strongest inter-plate coupling 298, 299 lateral growth rate 267 large crustal root beneath Southern volcanic gaps and fl at slab segments 289 out-of-sequence thrusts 266, 266 Alps 213, 228–9 Andes, central, deep structure 294–7 overall shape in profi le a tapered interpretation of mantle deformation cold lithosphere of Brazilian Shield to wedge 267, 268 below the Fault 229, 229 east 296–7 mechanical adjustments of late Cenozoic, became locus of slip crustal thickness 286, 294 oversteepened surface slope 267 between plates 228 lithospheric thinning beneath the thickened by tectonic shortening 267 linear trace extends across South Puna 293, 294 pore fl uid pressure Island 211, 213, 215 lithospheric-scale cross-section 296 and fl uid fl ow, sensitivity to Resolution segment, pull-apart basin 220, low wave speed zone beneath Los Frailes fl uctuations in 269, 269, 270 221 ignimbrite fi eld 296, 297 increasing and decreasing restraining bend 220, 221 refl ectors mark top of subducting Nazca mechanisms 268–9 southern segment, strike-slip partitioned Plate 294 proto-décollement zone 264 transpression 221, 223 seismic refl ection profi le across Taiwan 332, 333 COPYRIGHTEDsurface uplift and exhumation MATERIAL 243–4 294, 295 tectonic underplating 266, 267 unusually thin seismogenic layer 243 contrasts with those collected under top defi ned by trench slope break 267 vertical thickness of root below South fossil mountain belts 294, 296, 338, accretionary wedges see accretionary prisms Island 230 341, 364 accretive/constructive plate margins 92, 122 explanations of root geometry 230, distinct Moho conspicuously symmetric magnetic lineations 84, 112 230 absent 294 Adama Rift Basin 158, 159, 160, 161 Alpine–Himalayan belt 411 Andes, central and southern, general Aegean Sea 153, 162, 163, 164 Altyn Tagh Fault 316, 318, 321 geology 291–4 Afar Depression 155, 157, 203 Amazonia–Laurentia collision 372 Altiplano-Puna 288, 291 Afar hotspot, Ethiopian fl ood basalts 101, Americas–Europe and Africa, similarity of period of intense crustal 172 coastlines noted 2 shortening 291–2 African superswell 176, 394 Andean cordillera Quebrada Blanca Bright Spot 295, 296 age provinces compression in overriding plate and zone of low seismic wave speeds matched across S Atlantic 58–9, 59 mountain building 288 beneath 296

463 464 INDEX

Andes, central and southern, general Archean cratons 419 axial magma chamber 143 geology (cont’d) banded iron formations (BIFs) 350, 419 seismic evidence for 131–3 backarc region 288, 292, 294 general geology 350 Neogene shortening 292 granite-greenstone belts 350, 352–3 backarc basins 251–2, 252, 279–85 Chile Ridge currently subducting 294 greenstone belts 350 backarc lavas, compositional Liquiñe–Ofqui fault zone 294 high grade gneiss terranes 350 variation 282 models simulating deformation in 321 tonalite-trondhjemite-granodiorite in continental settings 284–5, 285 narrow forearc region 292 (TTG) suites 350 in context of Andean-type convergent Precordillera exposes Precambrian low velocity zones weak or absent 349 margins 279–80 basement 292 lowest surface heat fl ow of any most characterized by thin, hot Western and Eastern cordillera 288, 291 region 349 lithosphere 285, 296 Andes, Chilean, arc compression 263, 273 understanding of mineral deposits is form behind volcanic arc in the overriding andesites complicated 412–13 plate 279 calc-alkaline series 271 Archean metallogenesis, many aspects heat fl ow decreases with age 383 high-Mg (boninites) 353 require further investigation 419 Lau basin 280, 281, 281 anorthosite 350 Archean tectonics 349–61 model of crustal accretion for 282–3, massif-type 419 crustal structure 355–8 283, 284 anorthosite-mangerite-charnockite-granite horizontal and vertical tectonics 358–61 weaker mantle or thinner (AMCG) suites 363 Archean–Proterozoic boundary, change in lithosphere 254 anorthosite massifs 363 nature of lithosphere-forming magmas 282 anoxic event 409 processes 364 mechanisms postulated for formation Antarctica Arctic water, provides enhanced of 282–4 fi rst major build-up of ice 409 precipitation over Antarctica 411 roll-back mechanism 282, 300, 344 warming and deglaciation in late Arequipa Massif 292 sources of tension 282 Oligocene 409, 410 aseismic creep 233 model of formation generalized mid-Oligocene, surrounded by southern aseismic ridges 289 283–4 Ocean 408, 409 Asia, in continuum models of most associated with extensional tectonics separation from Africa 407, 409 indentation 321 and high heat fl ow 279 separation from India 408, 409 Asia, fi nite element models oceanic, crustal composition 280–1 sudden build-up of ice, mid- and late- effect of indenter shape on distribution of regions of crustal extension and Miocene 409, 410–11 deformation 322–3, 322, 323, 324 accretion 92 Appalachian fold belt–Caledonian fold belt lateral escape of crust 323 rifting of existing island arc along its of N Europe, continuity 58, 59 lithosphere especially viscous and length 280 Appalachian orogen, data collected in strong 323 structures corresponding to mid-ocean Newfoundland 340, 341 modeled as a viscous sheet 322, 322 ridges not always present exotic terranes accreted onto Laurentia asthenosphere 44, 48–51 281–2 margin 340, 341 anomalously hot 159 backarc spreading centers, backarc crustal many rifted from NW Gondwana 340, beneath Africa 176 accretion and subduction, 376 and mantle drag force 389 linkages 282 seismic refl ection data may mark old mantle melting point most closely Baikal Rift (System) 153, 153, 159 subduction zone 340, 341 approached 49, 49 Baltica 372 apparent polar wander curves 67–8 and relative movement of plates 49 Banda forearc see Australia–Banda arc APW for Gondwana, disagreement over Atacama Fault (System) 97, 292 collision zone details 68, 70 Atlantic ocean, reconstruction of continents Banda volcanic arc 330 positions of South Pole 4, 68 around 55–8 banded iron formations (BIF) 350, 361 continental drift has occurred 67, 69 atmosphere common in Archean cratons 419

paleomagnetic signature of plate removal and return of CO2 to 411, 412 Algoma and Superior types 419 convergence/divergence 67–8, 70 and seawater, changes in chemistry of 8 basalts 78 two methods of displaying paleomagnetic aulacogens (failed rifts) 153, 421 backarc basins, variation in data 67, 68 Australia, western, evidence for collision and geochemistry 283–4 arc magmatism 271–5 suturing of Yilgarn and Pilbara fl ood basalts general model of 252, 273–5, 274 cratons 365 continental 101, 101, 153, 154, 171, 172, depth to zone of seismicity 273 Australia–Banda arc collision zone 330, 331 172 mechanisms of melt generation Australian–Antarctica boundary, comparison tholeiitic 172–3 272–4 of models REVEL and NUVEL-1A mid-ocean ridge arc–continent collision 287, 330–2 109, 109 from slow- and ultra-slow spreading active examples 330 Australian–Pacifi c plates, and oblique ridges 140 oblique, Taiwan 287, 332, 333 continent–continent collision 228 refl ect fractionation environment after sequence of events 330 Avalonia 340, 341, 376 partial melting 140 Timor–Banda arc region 330, 331 rifted from Gondwana 376, 377 rift, enriched 172 INDEX 465

subducting, chemical reactions in 275, metamorphic core complexes 167, confi ning pressure, increasing with 276, 277 169, 170 depth 35 tholeiitic 175, 354, 354 Sevier Desert Detachment Fault 169, and differential stress 34–5 basin inversion 303 170 Griffi th theory of fracture 34 in association with strike-slip faulting 222, slip on low-angle normal faults 169 buoyancy forces arising from crustal 302 Snake Range Detachment 169, 170 thickening 323 caused by variety of mechanisms 221, Spring Valley Fault 169, 170 balanced by edge forces from 263, 303 Wasatch Fault Zone 169, 170 indentation 321 common criterion for recognition, null thin mantle lithosphere and anomalously buoyancy forces and lower crustal point or null line 303, 303 high heat fl ow 168 fl ow 181–3 compressional reactivation of pre-existing regional topography unusually crustal buoyancy forces 181, 181, 297 normal faults 303, 304 high 168 reduced or enhanced during Basin and Range Province 94, 153, 246 volcanic activity 168 lithospheric stretching 181,

broadly distributed deformation 162, value of Te low 184 182, 183 163 batholiths 271–2, 273 gravitational buoyancy forces 323, 326 Cenozoic deformation between two Gangdese batholith 309, 314, 315 and extension in Tibet 321 rigid blocks 162 Karakorum granite batholith 314, 316 strain delocalizing effects important at deformation fi eld revealed 162, 163, bauxite 422 low strain rates 180, 183 164 and laterite 61 thermal buoyancy forces 181,

recurrence time of major faults 165 bending resistance (RB) 389, 389 181, 192 relative motion, accommodation Benioff zone 84, 330 may contribute to horizontal deviatoric of 164 dip angles below central Andes 289, 291 stress 401 seismogenic layer, implies high double Benioff zones beneath Japan may dominate immediately after geothermal gradients and crustal arc 257, 257 rifting 183 thinning 165 earthquakes on 252, 253, 254, 254 Bushveld complex/intrusion 363, 416 Sierra Nevada and Colorado Plateau, length of 262, 262 Byerlee’s frictional strength law 39, 40 virtually no Cenozoic new interpretation 254, 255 deformation 162 variation in dips 262 calcium carbonate, secreted by oceanic signifi cant part of strain may be black shales organisms 411 accommodated aseismically 165 and Greenhouse Earth 410 California, northern three sub-provinces show distinctive and oil deposits 106–7, 107 Coast Ranges, contraction 163, 218, 234 strain patterns 163, 164 block rotation models 237–9 Great Valley–Sierra Nevada block, two prominent bands of high blocks defi ned 236, 237 westward movement 234 strain 162, 163 calculated fault slip rates 237 Pacifi c plate–Great Valley–Sierra Nevada Walker Lane and Eastern Californian elastic locking depth concept 238 microplate, zone of faulting Shear Zone 163, 164, 212 geodetic and geologic rates mismatch, between 234, 235 example of wide intracontinental rift 153, reasons for 238 California, southern 162 incorporation of elements of permanent accommodation of relative plate force required for rupturing 176 deformation 238–9 motion 162, 234 heterogeneous crustal thinning in block-to-block communication of clockwise rotation of motion 234, 237 previously thickened crust 165 rotation rates 238 crustal motion in, velocity fi eld crustal thinning non-uniform and potential problem, short-term geodetic 234, 236 infl uenced by pre-existing data 237–8 deformation zone broadens 234, 237 lithospheric structure 165 southern California 238 use of block models 236, 238 Death Valley, youngest examples of blueschist 275, 276, 281 see also Transverse Ranges, S. California large-magnitude extension 166 associated also with ophiolitic Canadian Cordillera 365 thick crust, history of convergence and suites 277 accretion of Intermontane Superterrane crustal shortening 165 boninites (high-Mg andesites) 353 337, 339 variation in Moho depths 165 border faults 156, 203 Omineca belt represents suture 337, small- and large-magnitude normal grown by propagation from short fault 338, 339 faulting 168 segments 202 Intermontane and Insular accommodation of large extensional high-angle 203, 204 Superterranes 336, 338, 341, 376 strains and crustal thinning 168 in lithospheric fl exure 183, 183, 184 major accretionary orogen 336, 338 asymmetric half graben and footwall Brazilian Shield 306 rifting events 336–7, 338 uplifts 168 cold lithosphere 296–7 Capricorn orogen 362, 365, 368

Cenozoic fault patterns 169, 170 underthrusting probably driven by simple carbon dioxide (CO2) Egan Fault 169, 170 shear 305 removed from atmosphere 412 extensional detachment faults 168–9 brittle deformation 34–6, 186, 187, 239 returned to atmosphere 411

low-angle, large-offset normal faults Anderson’s theory of faulting 35, 35 carbon dioxide (CO2) concentration, and evolution by fl exural rotation 169 by cataclastic fl ow 35–6, 35 changing climates 372–3 466 INDEX

carbonates continental confi gurations, early 112–13 diversity of species controlled by 63–4 deposited on top of glacial deposits 373 continental crust 5, 39 oceans as dispersal barriers 62–3 formed on sea fl oor 411 Archean, variety of tectonic models paleobotany 63 and reef deposits 61 proposed 354–5 and sea fl oor spreading 77–8 carbonatites 413 delamination of a dense eclogite continental extension 92 Carlsberg Ridge 97, 391 root 354 core complex mode 182, 183 catastrophism concept 2 problem with possible absence of and effects of ductile fl ow in lower Central American region reconstruction 57, subduction 354–5 crust 183 57 TTG suites, applicable to Late see also narrow rifts; wide rifts clockwise rotation of C American Archean 354 continental fl ood basalts 101, 101, 153, 154, blocks 57 becomes denser and more mafi c with 171, 172 Niger delta, post-rifting development 57 depth 23 continental lithosphere 184 space created for Caribbean 57 Conrad discontinuity 19, 20, 21 achieved tectonic stability during Chaco foreland basin 292 fl ow of heat from 23, 51–2 Proterozoic 363 charnockite 363 importance of vertical movements 5–6 base not well defi ned by seismological Chile Ridge, subducting 294 lower crust 51 data 349 climate composition and Poisson’s ratio 24, deforming, distribution of strain and changes in oceanic circulation 406–11 154, 159 within 239–41 deposits related to 421–2 difference between wet and dry 23 elastic thickness of 50 as a dispersal barrier 63 middle and lower crust 23–4 buried or hidden loads 50 land areas and climate 411–12 and the Moho (discontinuity) 19, 20 may be highly extended without latitude major controlling factor 60 natural division into three layers 21, 159, rupturing 162 coal 61 201, 296 and orogenesis 213, 287, 288 plate tectonics affects formation of 421 oldest, at beginning of Archean Eon 347 continental margins 192–3, 361 prime conditions for formation 421 pressure increases with depth 22 accretion to 312 process of coalifi cation 421 seismic velocities, variation with continental margins, rifted 153, 192, 193– Coast Plutonic Complex 338, 339 depth 19–21, 22–3 202 Coast Range ophiolite 342, 343 upper crust 23 carbonate hosted lead-zinc-barite ores Coast Shear Zone 338, 339 enriched in long-lived radioactive found 413 Columbia River fl ood basalts 171 isotopes 383–4 evolution of 198–202 composite terranes 335–6 xenoliths, samples of deep crustal nonvolcanic margins 196–8 examples 336, 338, 341, 376 material 22 volcanic margins 193–6 Conrad discontinuity 19, 20, 21, 29–30 continental deformation continental margins, transform 230–2 continent–continent collision 209, 228, 287, block models 237–8 history of 230–1 306–30 problem of determining specifi c see also Ivory Coast–Ghana margin between India and Eurasia 306–10, 308, mechanisms 239 continental reconstructions 55–8 309 continental deformation, measurement continents around the Atlantic 56–7 between Laurussia and Gondwana 377–8, of 39, 41 Euler’s theorem 55, 55 377 combined use of GPS and InSAR data 41, geometric reconstructions 55 general geology, Himalaya and Tibetan 219 Gondwana 57–8, 58 Plateau 312–16 large tectonic features, deformation 39, continental regions, heat fl ow in 383, 384 relative plate motions and collisional 235 continental rifting 413 history 306–9 use of GPS satellite measurements 39 leads to isolation of faunas 64 surface velocity fi elds and seismicity 309– Synthetic Aperture Radar (SAR) 39 models of rifting 186, 187–8, 189, 190, 12 continental drift 1–6, 55–71 191–2, 191 continental arcs apparent fi t of Atlantic east and west fi nal generation of new ocean dacites and rhyolites abundant 271 coasts 55 lithosphere 192, 192 structurally complex 271 continental reconstructions 55–8 continental rifts 153 continental areas, high velocities associated drifters and nondrifters, problems with zones of extension 92, 181–3, 182 with 394 both 5 continental suturing 327, 337, 338, 339, 365 continental collision 28 geologic evidence for 58–60 and homogenization of faunas by cross- and accretion, zones host range of correlation across juxtaposed migration 64 metalliferous deposits 418–19 margins 58 see also Indus–Zangbo suture mechanisms 318–30 paleoclimatology 60–1 continental transforms 211 continental underthrusting 319 paleomagnetism 64–71 deep structure of 224–30 indentation, lateral escape and paleontological evidence 61–4 Alpine Fault 228–30 gravitational collapse 319–26 continental rifting 64 Dead Sea Transform 224, 225 lower crustal fl ow and ductile continental suturing 64 San Andreas Fault 224, 226–8 extrusion 326–30 distribution of ancient plants and continents, tend to aggregate over cold precollisional history 318–19 animals 61–2 downwellings 301 INDEX 467

continuum models backarc, in oceanic settings, generation forms part of Arabian–Nubian plate and modeling of velocity fi elds 235, of 281–4 boundary 224, 225 236–7 changes in stress by normal Moho only slightly elevated 224 simulating deformation (use of viscous faulting 185 narrow zone of deformation 211, 214 sheet) 321–3 continental and oceanic, differences Deccan Traps 101, 101, 102, 171 contracting Earth hypothesis 380, 380 between 29–30 décollement 227, 264, 266, 267 no longer recognized as possible 380 depressed, downwellings produce regional decompression melting 172, 173, convection in the mantle see mantle, subsidence 395 202, 345 convection in overthickened, gravitational collapse deep sea cores, paleomagnetic investigations convergent margins 264 of 321 of 81 with high obliquity 96, 97 Proterozoic, general geology 361–3 correlation with results from lava metamorphism at 275–9 appearance of evaporites and red bed fl ows 81 chemical reactions in subducting deposits 361 Deep Sea Drilling Program (DSDP) Leg 3, basalts 275, 276, 277 Grenville provinces/belts 361, 370, 371, designed to test sea fl oor spreading tectonic inversion of extensional backarc 372 hypothesis 83, 84 and intra-arc basins 303 highly deformed regions, two deformation 246 core, the 33 types 361 at plate margins 92 inner and outer core 33 orogens with large ductile thrust brittle 34–6 liquid iron, reacts with mantle silicate in zones 361, 362 continuous vs. discontinuous 232–9 Layer D″ 33 quartzite-carbonate-shale accommodation of motion 232 core complexes sequences 361 determining degree of, problems formation of, Woodlark Rift 206 refl ects stabilization of Precambrian 233 metamorphic 167, 169, 170, 358 crust 361 model sensitivities 236–9 oceanic 138 thickened by overplating and models involving continuous velocity core–mantle boundary 21, 30, 33, 395 underplating 273–4, 274 fi elds 232–3 low velocity regions at 394 see also continental crust; oceanic crust regional velocity fi elds 232 origination of some plumes at 399–400 crust and mantle rheology 33–42 relative plate motions and surface possibility that heat fl ux is nonuniform brittle deformation 34–6 velocity fi elds 233–6 76–7 deformation in the mantle 41–2 rigid block models 233 Côte d’Ivoire–Ghana marginal ridge ductile deformation 36–7 contractional, 264–70, 304–6 evidence of folding and faulting lithospheric strength profi les 37, 39 see also fold and thrust belts associated with dextral motion measuring continental deformation 39, creep 34 231–2 41 ductile 36–7 formation of pull-apart basins 232 strain (elastic limit and yield stress) 34 extensional 92, 154 cratonic mantle lithosphere, general stress (deviatoric, differential, intra-plate 92 characteristics 349–50 principal) 34, 176, 177, 401 mantle 41–2 faster seismic velocity 349 crustal accretion plate-tectonic style 238–9 cratonic nucleii, formation of 347 backarc and mid-ocean ridge settings, and stress 34 cratonic roots 347, 364 differences 285 strike-slip, accommodation of cool, when reached current Lau basin 282–3, 283, 284 strain 241 thickness 348 slow-spreading ridges 144 weak and strong crust models distinctive composition 351 crustal thickening 192, 322, 326, 345 225, 241 kept thin by convective heat transfer from crystal fractionation 416 see also continental deformation underlying mantle 348 deformation front, accretionary prisms 264, modifi cation by terrane collision and D″ layer 31, 33, 106, 395–6 265 thickening 352 acts as thermochemical boundary dehydration embrittlement 257–8 opinions divided on construction layer 398 delamination methods 351–2 marked lateral and vertical variations of a dense eclogite root 354 other processes contributing to root within 395–6 of thick ocean crust, Early Archean 355, formation 351–2 as mechanical boundary for mantle 355 Proterozoic evolution 364 convection 41 Denali Fault 339 subduction zone mechanism for 352, 353 nature of, three different regions 395–6, desert deposits 61 Cretaceous Superplume 106–7, 107 396 destructive plate margins 92, 94 acceptance not universal 107 ultra-low velocity zones (ULVZ) 395, 396, ancient 112 creation of numerous seamounts/ocean 398, 398, 399 deviatoric tensional stress, and rift plateaux W Pacifi c 106, 171 Dead Sea Transform 241 initiation 176, 177 crust 22–7, 78, 185, 188, 188 Arava Fault, seismic and refraction diamonds, and kimberlites 419–20 Archean 347 data 214, 224, 225 diapiric models 358, 359 model of evolution 355, 355 extension not dominant in shaping deep problems with 361 modern analogues 354 structure 224 dispersal barriers 62–3 468 INDEX

dome-and-keel provinces 356–8 dynamic recrystallization 36 Himalayan–Tibetan orogen, faulting Eastern Pilbara craton, Australia 356–8, superplastic creep 36–7 style 312, 313, 316 356, 357 ductile extrusion 327–8 nodal planes 13, 13, 14, 15, 15 felsic volcanism 358 ductile fl ow, and vertical decoupling of obtaining a focal mechanism solution 13– horizontal tectonic models for 358–9 lithosphere 327 14, 13, 14 Mt. Edgar Dome and granitic ductile shear zones 233 show South American plate in complex 357, 357 compression 289, 290 nine granite domes with TTG Earth 398 Transverse Ranges, S. California 219, 220 granitoid remnants 356 climate and changes in oceanic earthquake hypocenters preservation of stromatolites 358 circulation 406–11 beneath Wetar Strait and Banda arc 330 shear zones and ring faults 358 infl uence of plate tectonic distribution with depth, central synclinal tracts of greenstone between processes 412 Andes 289, 291 granitoid domes 356, 358 early phase of melting and earthquake location 11–12 three-stage diapiric model 359, 359 differentiation 52 earthquake seismology 10–19 downgoing slab heat fl ow through unit area of surface 52 earthquake descriptors 10 earthquake activity associated with 254–9 possible origins of the magnetic fi eld 77 mechanism of earthquakes 12 (a) fl exural bending of the secular cooling of 364 seismic tomography 17–19 lithosphere 254–5, 256 Earth, composition of 21–2 seismic waves 10–11 (b) earthquakes generated by thrust estimates can be made from earthquakes faulting 255, 255, 256, 257 meteorites 22 shallow focus 93–4, 93 (c) in the Benioff zone 257–8, 257 formation 21 and ocean ridge topography 122, 122 (d) sudden phase change from olivine mean atomic weight 22 and structure of subduction zones to spinel structure probable composition 22, 22 252–9 (transformational/anticrack radioactive decay during early East African Rift system 153, 175 faulting) 255, 258 history 52 continental fl ood basalts 101, 101, 153, deep earthquakes, triggering of and rheological layering 52 154 257–8 Earth, velocity structure 19–21 domal uplifts and pervasive no relationship between age and built up by recording body wave travel volcanism 159 mantle penetration 259 times 21 Eastern branch principal stress directions of (c) and Conrad, discovery of further central and northern Kenya, rifts (d) 258–9, 258 discontinuity 19, 20, 21 slightly more evolved 154, 202 stress type and resistance during discovery of Moho 19 change of orientation 177–8 descent 259, 259 Gutenberg discontinuity 21 imaging upper mantle beneath 175–6, downgoing slab, thermal structure of 259– knowledge of internal layering 19 176 62 low velocity zone (LVZ) 21, 50 Kenya Rift, shallowing of controlling factors 260–2 velocities increase abruptly at the asthenosphere–lithosphere adiabatic heating 261 Moho 21 boundary 203 age and thickness of descending earthquake distribution 92–4 magmas derived from at least two slab 260 epicenters of large magnitude mantle sources 174 conduction of heat into slab from earthquakes 92, 93 Tanzania, effects of pre-existing asthenosphere 260 earthquake focal mechanism (fault plane) weaknesses on geometry of frictional heating of upper and lower solutions 12–14 rifting 154, 202, 203 surfaces 260 Aleutian arc 256, 257 lakes of 413 latent heat associated with phase ambiguity in 14–17, 14 low velocity anomaly, Adama Rift transitions of minerals 261 identifi cation of different types of Basin 159, 160, 161 rate of subduction 260 faulting 16–17 narrow intracontinental rifts 154, 155 ductile deformation 36–7, 186, 187, 189, P wave radiation pattern, types I and II occurrence of continuum of mafi c 239, 244 source mechanism 17, 17 rocks 172, 173 by slow fl ow or creep in the solid S wave radiation pattern, type I rift–rifted margin transition 154, 202–4 state 36, 233 source 17, 17 see also Main Ethiopian Rift diffusion creep 36, 41, 185 S wave radiation pattern, type II East Pacifi c Rise 138 Coble creep 36 source 17, 17 black smokers and white smokers 413 Nabarro–Herring creep 36, 38 solution of a normal fault 16, 16 compositional variation of basalts 140 Lalla Rookh–Western Shaw structural solution of a thrust fault 15, 15 fast spreading rate 122, 122, 128 corridor 356, 358 use of Anderson’s theory of horst and graben topography 123 plastic fl ow, occurs by dislocation faulting 16, 35, 35 hydrothermal vent fi elds 131 glide 36, 37 Basin and Range 163, 234 magma chamber 145 power-law creep (dislocation creep) 39, earthquakes occurring on plate only short lengths of pure melt 133 41, 51, 185 interfaces 97 region with high melt fraction very dislocation climb 36, 38 fault planes and auxiliary planes 12, 13 small 132 INDEX 469

studies show evidence for top at epicenter 10, 10 fl uid fl ow and changes in pore fl uid varying levels 131–2 epicentral angle 10, 10 pressure, importance in accretionary use of multi-channel expanded spread Etendeka fl ood basalts 101, 101 prisms 267–9 refl ection profi ling 132, 132 Ethiopia, area of occurrence of most large fold mountain belts MELT experiment 127–8, 128 earthquakes 155, 157 continuity of and continental drift 58, 59 multi-fault zones 148–9 Ethiopian fl ood basalts 101, 158, 171, 172, young, distribution of 3, 3 segmented by non-transform ridge 172 fold and thrust belts 264 discontinuities 134–5 Ethiopian Plateau foreland 292, 293, 302 seismic refraction experiments 125, 125 uplift and anomalously hot Himalayan 315, 318–19, 327 Easter–Line Islands track 99, 102 asthenosphere 172 thick- and thin-skinned 292, 293 Eastern California Shear Zone 212, 226, volcanism coincided with opening of Red forearc basins 251, 267, 332, 333, 334 238, 242 Sea and Gulf of Aden 158 forebulge 302, 313 Eastern Pilbara craton, Australia 356–8, 356, European Alps 287, 306 foreland basins, formation of 302, 316 357 evaporites 61, 422 fl exure of continental craton 302 development of Warrawoona Greenstone expanding Earth hypothesis 380–2 foreland fold and thrust belts 293, 302–3 Belt 358, 360 calculation of ancient moment of inertia piggyback basins 303 dome-and-keel structural style of Earth 381 foreland fold-thrust belts, modes of explained 358–61 calculation of ancient radius of shortening 304–6 horizontal tectonic models 358–9, 360 Earth 382 Andes, differences of style/mode along- vertical tectonic models 358, 359 strike 305–6 eclogite 275, 276 Falkland–Agulhas Fracture Zone 90 thermomechanical experiments 305–6, appears to be present in cratonic Famatina arc terrane 375, 376 305 lithosphere 350 Farallon Plate 119, 120 underthrusting of the shield 306 Phanerozoic 366–7, 369 subducted and sinking 395 central Andes, contractional in situ, oldest examples 368 fast-spreading ridges 122, 122, 135, 140 deformation 304 economic geology 412–22 axial high and magma chamber creation of doubly vergent thrust autochthonous and allochthonous below 141 wedges 243, 293, 304 mineral deposits 413–20 brittle–ductile transition 145 décollement (detachment) surfaces 304 deposits classifi ed according to plate development of melt lens at 133, 134 dipping towards hinterland 293, 296, tectonic processes 412 fi rst order segmentations 135 304 deposits related to climate 421–2 magma supply rate 141 lateral growth of thrust wedges 304 deposits of sedimentary basins 420–1 origin of oceanic crust at 142–4 pure shear mode 304 geothermal power 422 second order segmentations 135 simple shear mode 304–5 edge force mechanism 391–3, 391 create off-axis scars on spreading in thin-skinned and thick-skinned consistent with pattern of intraplate crust 135, 137 belts 293, 304 stress 392 third and fourth order segmentations fractionation 173 more acceptable thermodynamically 392 short-lived 135 fracture zones 112, 135 plates move in response to edge faulting interpretation as large scale strike-slip forces 392, 392 normal 35, 141, 155 faults 86 reconcilable with present plate oblique-slip 220–23, 228 Mid-Atlantic Ridge, focal mechanism motions 392 strike-slip 35, 211, see also strike-slip fault solutions for earthquakes occurring ridge-push force 392 styles near 88, 88 slab-pull force 392 thrust 35, 263, see also fold and thrust oceanic 148–51 trench suction force 392 belts dredging, rocks recovered 149 El Salvador Fault Zone, features common to Fennoscandia, illustrating isostatic leaky transform faults 150, 151 extensional step-overs 214–15, 217 rebound 45, 46 major, transverse ridges associated Cocos–Caribbean plate convergence 215, ferromanganese nodules/encrustations 413, with 150, 151 217 415 mark both active transform segment Río Lempa pull-apart basin 215, 217 Finnmarkian Orogeny 376 and trace 148 elastic deformation 10 fi xed hotspots hypothesis 102, 103 strong and weak portions 151 elastic locking depth concept 238 Flemish Cap 200–1, 200 ultramafi c intrusions probably contain elastic materials, strain and Hooke’s law 34 continental crust, formed during minerals 419 elastic rebound theory, and earthquakes 12, Mesozoic rifting 200, 201 12 Galicia Bank, transition zone 200, 201 Gakkel Ridge environmental change 405–12 Newfoundland margin lacks a transition crust serpentinized and tectonized mantle changes in oceanic circulation and Earth’s zone 200 peridotite 144 climate 406–11 strong regional west-dipping S-type high levels of hydrothermal activity at changes in sea level and seawater refl ection 200, 201 certain locations 131 chemistry 405–6 fl exural backstripping 199, 199 lack of correlation with spreading land areas and climate 411–12 fl exural bulge 251, 252, 254–5 rate 140–1 470 INDEX

Gakkel Ridge (cont’d) GPS (Global Positioning System) data, global heat fl ow 383, 383, 384 long-lived spreading event, magma measuring plate movement 97 ocean ridges 129–31 derived from mantle depths 133 GPS satellite measurements 39 high heat fl ow associated with 383, 383 marked along-axis contrast in magma Grampian Orogeny 376 oceanic, most must originate at sub- supply 142 granite, fi rst appearance in geologic crustal levels 384 segmentation of 136 record 362 Precambrian 347–9 ultraslow eastern sector, large volcanic granite bodies, mineralization associated terrestrial 51–3 centers 142 with emplacement 419 Heirtzler et al. long-term geomagnetic ultraslow spreading rate 123, 124 granite-greenstone belts 350, 352–3 timescale 82, 83 Galapagos Islands 399 crustal structure 355–8 extended back to 160 Ma 84 evidence for ridge propagation dome-and-keel provinces 356–8, 356, high-grade gneiss terranes, Archean mechanism 147, 147 357 cratons 350 Galapagos Rift, hydrothermal structural styles/outcrop patterns 307, high-Mg olivine and high-Mg circulation 130 314, 355–6 orthopyroxene 351 Ganga foreland basin 312, 316 granodiorite 273 possible mechanisms allowing segregation Geikie, A., “the present is the key to the granulites 277 and accumulation 351, 352 past” 2 Greenhouse Earth 406 Himalaya and Tibetan Plateau, general geodynamo global cooling not associated with geology 312–16 can exist in either of two states 76–7 decrease in volcanism 107, 412 active shortening north of the

mathematical formulation of not high levels of CO2 and enhanced volcanic plateau 316 possible 75 activity 412 Bangong–Nujiang suture, and Qaidam numerical modeling 75–6 transition to Icehouse Earth 409 Basin 307, 316 geomagnetic fi eld 21 warm oceans led to formation of black deformation at northern margin of generated in outer core 33, 75 shales 410 Tibet 316 no general theory of origin 75 greenhouse effect, enhanced 106 active strike-slip faults 316 past and present 66–7 greenhouse gases, atmospheric forces contributing to present stress believed to originate through concentration of 106, 406 state 325, 326 magnetohydrodynamics 66, 75 greenstone belts a foreland-propagating fold-thrust computing apparent location of the Abitibi greenstone domain 352, 353 system 313 paleopole 66–7 Archean Higher Himalaya 312–13 progressive changes with time, secular hosting volcanogenic massive imbricated thrust slices variation 66 sulfi des 419 accommodate some post-collisional remanent magnetization directions 67, nickel-sulfi des hosted by shortening 312 372 komatiites 419 Main Boundary Thrust 312, 314, 324, geomagnetic polarity timescale greenschist facies metamorphism 350 325 for past 160 Ma 83–4, 85 stratigraphic groups Main Central Thrust 312, 314, 328 Plio-Pleistocene 79, 80 clastic sediments 350 Main Frontal Thrust, carries rock geomagnetic reversals 74–7 intermediate and felsic rocks 350 South into fl exural foredeep 213 by mid 1960s concept widely accepted 75 tholeiitic and komatiitic lavas 350 and major fault systems 312, 314, 315 estimated frequency over last 160 Ma 77 Gulf Stream 406 merge downwards into décollement, low during plume episode 107 and ice sheets in North Atlantic Main Himalayan Thrust 313, 315 occurred at variable rates in past 76, 77, region 409 Sichuan Basin, relatively undeformed 316 85 Gutenberg discontinuity 21 South Tibetan Detachment System 313– timescales 79, 80, 81 14, 314, 328 geosynclinal theory 7–8 Hawaii 423 Tethyan zone gneiss domes, origin not geothermal power 422 Hawaiian Islands fl ood basalts 171 well understood 314 glacial deposits 61 Hawaiian–Emperor seamount chain 99, 99, Kangmar gneiss dome 314, 315 glaciation, global, Late Proterozoic 372 102 Transhimalayan zone, Gangdese global cooling change in direction 398 batholith 309, 314, 315 around Miocene–Pliocene boundary 410, major bend 102, 103 see also Indus–Zangbo suture 412 may have migrated south 102 Himalaya and Tibetan Plateau, general not associated with decrease in heat fl ow geology, deep structure 316–18, 317 volcanism 107, 412 backarc basins 279, 383 below Himalaya, crustal décollement 316 Global (Digital) Seismograph Network continental, from sources at shallow central Tibet, deformation below (GSN) 11 depth 384 Bangong–Nujiang suture 315, 317 gneiss domes 314 high 159–61, 159, 161, 171, 279 Moho Gondwana 370 and hydrothermal circulation 129–31 areas of shallowing 317, 318 accretion of terranes 376 implications of 382–4 below Himalaya 315, 316 Grenville belt traceable through 372 generally decreases with age of south of Bangong–Nujiang suture, reconstruction 57–8, 58 crust 383 downwelling of lithosphere 318, 319 INDEX 471

Tibetan Plateau, studied as part of oceanic intra-plate activity, linear island Indus–Zangbo suture 308, 309, 314–15, INDEPTH project 315, 316–18 and seamount chains 99–100, 99 328 underthrusting of Indian lithosphere 318 partial melt entrained from ULVZ 399 now forms southern boundary of Tibetan Himalayan–Alpine system 306 predicted traces in Atlantic and Indian Plateau 309, 309 Himalayan–Tibetan orogen 287, 306, 307, oceans 101, 102 separates Indian Plate rocks from rocks 312–16 and rise in sea level 405 of Lhasa terrane 314–15 built on collage of exotic material welded secondary plumes, on south Pacifi c intra-plate areas, relatively aseismic 94 to Eurasian Plate 309 superswell 400 intracratonic rifts, carbonate hosted mechanisms of continental collision 318– three types in terms of depth of lead-zinc-barite ores 413 30 origin 399 island arc systems, general continental underthrusting 319 hydrothermal circulation 28, 129–31 morphology 251–2, 252 indentation, lateral escape and hydrothermal processes 413 forearc basin 251 gravitational collapse 319–26 hydrothermal vent fi elds 131 forearc region 251, 264 lower crustal fl ow and ductile general convexity of 251 extrusion 326–30 Iapetus Ocean, opening up 376, 376 typical of margins of shrinking precollisional history 318–19 Icehouse Earth 406 oceans 251 relative plate motions and collisional transition to, Eocene–Oligocene island arcs history 306–9 boundary 409, 410 inner magmatic arc 251 composite belt evolved since the Iceland 423 large positive anomaly 252 Paleozoic 306, 378 Iceland hotspot 101, 103, 399 mature, thicker crust 271 new subduction zone beneath initiation and track 102–3, 104 and melt ascent velocities 275 Lhasa 308, 309 igneous provinces 59, 60 outer sedimentary arc 251 results of fi nite element model 324, 325, igneous rocks, compared, Archean and and remnant backarc, enclose a backarc 326 Proterozoic belts 362–3 basin 251–2 simulation of deformation of Asia, incompatible elements 31, 174, 350 isostasy 6, 34, 42–8 continuum models 321–2 indentation 319–23 Airy’s hypothesis 43, 43 surface velocity fi elds and seismicity 309– continuum models 321 fi rst recognized in 18th century 12 evolution of indentation model 320–1 42, 42 accommodation of convergence 310, indentation experiments 319–20, 320 fl exure of the lithosphere 44–5 312 development of pull-apart basins 320, elastic response to loading 44, 44 deformation within Tibetan plateau 320 fl exural isostasy 45 and margins 307, 310 lateral extrusion, resulting oceanic lithosphere when loaded by a lateral escape eastward 310, 311 extension 320, 320 seamount 45, 45 northward motion a series of irregular India–Eurasia collision 306–7 over time may act in a viscoelastic steps 311 deformation extended deep into manner 44 penetration of India into Asia Eurasia 318 realistic models involve regional 309–10 exposures of ultra-high pressure (UHP) compensation 44 style of active faulting in 310, 312, 313 minerals 308 isostatic rebound 45–6 Tibet 326 Indian Plate controlled by viscosity of extension may result from gravitational accommodation of underthrusting 319 asthenosphere 45 buoyancy forces 321 formation of Himalayan fold and illustrated by Fennoscandia 45, 46 Longmen Shan region, accommodation thrust belt 318–19 rate provides estimate for viscosity of of lateral crustal motion 311, 327 mechanisms assisting upper mantle 45–6 see also India–Eurasia collision underthrusting 317, 319 Pratt’s hypothesis 43–4 Himalayan-type orogens 92, 209, 287 resisted shortening during collision 318 mechanism of isostatic Holmes, A., mechanism of continental underthrust Tibet 318 compensation 43 movement 5, 6 main collision preceded by smaller presence of subsurface compensation hotspots 99–103, 401 collisions 308 confi rmed 42, 42 and absolute motion of plates 98–9, 98 collisions marked by suture zones 307, principle of 42–3 criteria for distinguishing primary 308 tests of 46–8 hotspots 101, 399, 400 main terranes and sutures 308–9 forward modeling 46 distribution 100 possible timing of initial collision 307–8 free air, Bouguer and Airy isostatic fi xed hotspots hypothesis 102, 103 reconstruction of paleolatitude of Indian anomalies 47 island chains 99 plate 307, 308 gravity anomalies 46–7 possible explanation of origin 100 Indo-Australian plate, oceanic lithosphere more sophisticated test 47 lack similarity 100 subducted northward at Java Trench Ivory Coast–Ghana margin 231–2 and Large Igneous Provinces (LIPs) 100– 330, 331 formation 231 1, 101 Indonesia, eastern, evidence of northward main phases of evolution 231, 232 models of hot, low viscosity plumes 399, subduction of Indian oceanic narrow continent–continent transition 400 lithosphere 330, 331 zones 231, 231 472 INDEX

Ivory Coast–Ghana margin (cont’d) lateritic deposits, as source of nickel 421 lithosphere–asthenosphere interactions, represents a fossil margin 231 Lau basin, model of crustal accretion crucial component of rift see also Côte d’Ivoire–Ghana marginal for 282–3 systems 192 ridge Central Lau spreading ridge 283 lithosphere–asthenosphere interface, not Izu–Bonin–Mariana arc system 260 East Lau spreading ridge, diminished melt sharply defi ned 50 magma, compositional trends along arc supply 283 lithospheric fl exure 34, 44–5, 50–1, 183–4 axis 271, 272 region of enhanced melting 282–3, border faults 183, 183, 184 283 defl ection of crust by slip on normal Japan arc, thermal model for subduction region of hydrated mantle 282, 284 faults 184 zone 257, 258 roll-back of Pacifi c slab beneath Tonga and fl exural isostatic compensation 184 Japanese island arc system, compositional trench 282, 284 formation of large-magnitude normal trend apparent 271 spreading centers 282, 283 faults 184 Juan de Fuca Ridge 74, 147 Laurasia, supported varied tropical fl ora 63, plate fl exure 183–4 63 strong plates and weak plates 184 Kaapvaal craton 364 Laurentia 370 and sediment thickness in foreland inventory of mantle xenoliths 350 accretion of terranes 376 basins 302 Karoo fl ood basalts 171 Apparent Polar Wander path, used as lithospheric mantle, progressive decrease in Kenya Dome 158, 172, 175 reference path 372 degree of depletion since Kenya Rift, shallowing and increase of rifted away from South America and Archean 364, 364 magmatic activity 203 Baltica 376, 376 lithospheric strength profi les 37, 39 Kenya, southern, magma source 174, Laurussia 370 continental lithosphere, potential 175 lawsonite 275 effects of water on layer strength Kenyan fl ood basalts 171–2 leucogabbro 350 39, 40 Kerguelan Plateau 171, 171, 172 leucogranite 313 may be characterized by “jelly sandwich” kimberlite pipes 30, 419 Liquiñe–Ofqui Fault, Chile 97 rheological layering 37 kimberlites 419–20 lithosphere 44, 48–51, 184, 185 through oceanic and continental komatiites 350, 352 Archean, formation of 348, 351–5 lithosphere 40 formation of 353–4, 353 granite-greenstone belts 352–3 lithospheric strengthening 178 best thought of as a viscoelastic lithospheric stretching 179–81 Lachlan orogen 287 layer 51 crustal thinning or necking 179, 191 growth by magma addition and brittle upper layer 51 heat advection 179 sedimentation 342, 343, 344, 344 deforming 96, 97 high strain rates tend to localize

types of base and precious metals elastic thickness (Te) 50–1 strain 179

formed/preserved 419 overestimates of Te 51 thermal and mechanical effects, different orogenic gold mineralization 419 existence of large lateral movements 74, strain rates 179, 180, 181 land areas and climate 411–12 86 divisions of lithosphere 179, 180 albedo of land depends on vegetative horizontal force required for lithospheric thinning, in backarc cover type 411 rupturing 176 regions 340 global cooling near Miocene–Pliocene layer deforming by plastic fl ow 51 lithospheric weakening 178 boundary 412 lithospheric cooling strain-induced 194–8 ice/snow cover has high albedo 411 GDH1 model 129, 129–30, 130 Lofoten–Vesterålen continental margin 193, land and sea breezes 411 half space model 129, 130 194, 195 monsoonal climates 411 plate model 129, 130 crustal structure shows moderate uplift of Tibetan Plateau 411–12 lowest part deforms by power-law extension 193 weathering of carbonates and creep 51 Louisville Ridge 99, 102 silicates 411, 412 rheological stratifi cation of 37, 39, 40, Love waves 10, 11, 18 Large Igneous Provinces (LIPs) 100–1, 101, 188–92 low velocity zone (LVZ) 21, 50 171–2, 171, 412–13 seismogenic thickness 51 lower crustal fl ow and ductile mafi c magma, large outpourings thin beneath ocean ridges 49 extrusion 326–30 environmental consequences of underlain by asthenosphere 49 thermomechanical models 327–8, 329 eruption 172 vertical decoupling due to ductile mantle source needed 172 fl ow 327 mafi c dike swarms not all are associated with zones of see also oceanic lithosphere emplacement into Archean cratons and extension 171 lithosphere–asthenosphere boundary 178, cover rocks 362–3 oceanic plateaux within oceanic 328 MacKenzie dike swarm 362–3 plates 171, 171 controlled by temperature 129 magma chambers 140 some continental fl ood volcanics form defi ning location of 349 abundance of volatiles in uppermost quickly 172 rising beneath a rift 202 part 143–4 submarine plateaux, formation of 172 shallowing of and increase of magmatic deep, plutonic rocks crystallized residua within continental plates 171, 171 activity 203 of 272 INDEX 473

melt lens development, fast-spreading earthquakes round volcanoes and mantle, convection in 384–8, 395 ridges 133, 134 fi ssures 156, 158 convection process 384–6 model for slow-spreading ridges 133, 134 extension in central and southern convection in a fl uid 385, 385 magma composition, infl uenced by local part 203 convective fl ow in mantle, nature conditions 271 Gulf of Aden, transition to slow- problematic 384–5 magma underplating 345 spreading mid-ocean ridge 154, 203– mantle heated from below and from magmatic arcs, accreted material 264 4 within 385–6, 385 magmatic terranes 335 high-angle border faults, chains of stabilization of convective pattern 386 magmatism volcanic centers 203, 203 without a lower thermal generation of ore minerals 413 localization of magmatism and boundary 386, 386 mafi c 172, 362–3 faulting 203, 203 evidence for 393–6 and initiation of rifting 192, 413 low velocity anomaly, Adama Rift the D″ layer 395–6 large pulses affecting cratonic Basin 159, 160, 161 seismic tomography 393–4 roots 351 northern superswells 394–5 mafi c and ultramafi c 416 faults and segmentation pattern 156 feasibility of 386–7 plume-related, and assembly of seismicity of rift segments 155–6, 157 mantle convection cells 396–8 supercontinents 403 mantle 30–3 nature of 396–8 weakens lithosphere and causes strain composition 31 layer D″, as thermochemical boundary localization 192 bulk mantle composition 31 layer 398 see also volcanic activity extent 30 plate mode, crucial in cooling the magnetic anomalies 73, 112 fi rst 3-D seismic velocity models mantle 397 linear anomalies, development over ocean for 393 plate and plume modes, origins in crust 81, 83 low velocity zone 21, 31–2 thermal boundary layers 396–7 marine 73–4 molten material and lower seismic plume mode, releases heat from the Juan de Fuca ridge 74, 76 velocities 31–2, 49 core 397 juxtaposition of large positive and partial melting 32 stabilization of bottom of plume/ negative anomalies 73 seismic effects 31–2 thermal upwelling 398 offset along fracture zones 86 lower mantle 32–3 viscosity greater in lower mantle 397–8 used to date oceanic lithosphere 79 division into D′ and D″ layers 395 upwellings profi le and model over southern layer D″ often characterized by probably independent of Mid-Atlantic Ridge 82 decrease in seismic velocity 33 supercontinent cycle 403 magnetic anomaly pattern, variation more enriched in incompatible two major, centered on expanding 79, 79 elements 31 rings of subduction zones 397 magnetic domains 65 onset of vertical upwelling, central vertical extent of convection 387–8 magnetic fi elds, generation of 65 Pacifi c and S Africa 41 infl uence of mantle transition magnetic lineations 78, 78, 84, 112, 281 partially molten material in 33 zone 387–8 interrupted at major fracture zones 73, thermal and/or compositional mantle, deformation in 41–2 73 heterogeneity 33 diffusion creep shown on magnetic maps before true top, further zone of seismic anisotropy probably dominant mechanism 41 signifi cance realized 78 and horizontal fl ow, 41–2 power-law (dislocation) creep 41 source probably in basaltic oceanic variations in shear wave velocity mantle drag layer 2 73–4 small 393 cellular convection 391, 391 symmetrical about ridge axes 73, 75 melting to produce basaltic liquids dependent on asthenosphere velocity 389 magnetic profi les close to mid-ocean ridge beneath rifts 173, 174 needed for Phanerozoic plate crestal regions 81, 81, 82, 82 seismic structure 30–1 motions 391 magnetostratigraphy 79–84 lithosphere 30 mantle lithosphere, thinning of 202 ocean magnetic anomalies used to date low velocity zone 30 outpaces crustal thinning 203 oceanic lithosphere 79 lowermost layer at core–mantle mantle melt generation conditions Main Ethiopian Rift boundary, layer D″ 31 354, 354 Afar Depression major discontinuity marks beginning mantle plumes 196 border faults abandoned as magmatism of transition zone 30–1 ancient 351–2 accommodates extension 203 ultra low velocity zone 31 ascent of buoyant mafi c material in 364 rift functioning as slow-spreading mid- transition zone 32 events through time, two types 403 ocean ridge 203 major velocity discontinuities, top and and formation of komatiitic and tholeiitic Afar hotspot, Ethiopian fl ood basalts 101, bottom 32 basalt 354, 354 172 phase transformations, may defi ne and hotspots 100 broadening of low velocity zone upper and lower bounds 32 may form large ocean plateaux 172 consistent with propagation 160 pressure/temperature conditions and may tap deep undegassed mantle extension across accommodated olivine phase transformations 32, 32 sources 172 aseismically 155 upwelling beneath rifts 175–6 mantle rheology studies 41 474 INDEX

mantle transition zone studies show low velocity zone in lower ridge jump implied 90 chemical reservoirs can be preserved 388 crust 132–3 Muskox intrusion 363 and convection in the mantle 387–8 thin crust, in vicinity of fracture may not be barrier to mantle-wide zones 145 Nankai Trough, large, active accretionary convection 388 mid-ocean ridge basalts (MORB) prism 264, 266 numerically modeled in three chemistry of, many alternatives 140 narrow rifts, general characteristics 153, dimensions 388 contain phenocrysts 140 155–61 place where solid state phase changes xenocrysts of deep-level origin 140 asymmetric rift basins fl anked by normal occur 387 mid-ocean ridges faults 155 variations in seismic velocity small 393 accretionary processes at crests 144–5 asymmetric half grabens 154, 155 Mariana arc system, underlain by thin brittle–ductile transition 145 segmentation of rift valley 155, crust 263, 271 creation of new mineral deposits 413 156 Mariana forearc 265, 277 low velocities associated with 394 syn-rift units 155, 156 Mariana trench/trough 250 metalliferous deposits at ridge and crustal buoyancy forces 181, 182 crustal thicknesses 281 crests 131 high heat fl ow and low velocity, low lithospheric bending 255, 256 uplift and expansion and contraction of density upper mantle 159–61, 159, subduction zone 262, 263 upper mantle material 128–9 161 Mariana volcanic arc, thin crust under active see also fast-spreading ridges; slow- domal uplifts and pervasive part 271 spreading ridges; ocean ridges volcanism 159 massive sulfi de deposits 413, 415–16 Middle America accretionary prism growth local crustal thinning modifi ed by stratiform massive sulfi de deposits rate 267 magmatic activity 158, 159, 160 Besshi-type deposits 417, 418 Middle East, large proportion of crustal thinning beneath main axis Kuroko-type ores 417, 418 hydrocarbon reserves located 158 Median Tectonic Line, SW Japan 97 in 421 crustal velocity structure beneath Mediterranean Sea, isolated by growth in ice results from specifi c pattern of plate Adama Rift Basin 158, 159 volume 409 interactions 421 display short-wave positive Bouguer mélange, a chaotic mixture of rocks 268 migmatite 313 gravity anomalies 158, 160 MELT (Mantle Electromagnetic and proposed mechanisms of formation 277 gravity data provide evidence for Tomography) experiment, East textural term 277 modifi cation by magmatism 154, Pacifi c Rise 127–8, 128 mineral deposits, Proterozoic 419 158, 160 Mendocino fracture zone 119, 120 mineralization high velocity lower crustal layer 158 Mendocino Triple Junction 212, 226, 228 exhalative 413, 415 shallow seismicity and regional mesosphere 51, 52 plate boundary-related tectonic stresses 155–6, 158 metallogenic provinces 60 settings 413, 414 earthquakes concentrated round metamorphic core complexes 167, 169, 170, Moho (Mohorovicˇic´ discontinuity) 294 volcanoes and fi ssures 156, 158 358 in ancient accretionary orogens 340 earthquakes defi ne seismogenic metamorphism marks crust–mantle boundary 19 layer 155 at convergent margins 275–9 offset by San Andreas Fault 226, 226 extension across Main Ethiopian Rift regional 276, 277 seismic Moho and petrologic accommodated aseismically 155 meteorites 22 Moho 144 seismicity pattern, northern Ethiopian microplates, in the southeast Pacifi c 147–8, velocities increase abruptly at 21 Rift and fl anks 155–6, 157 148 Mohr–Coulomb fracture criterion 267 natural hazards 422–3 tectonic elements of Juan Fernández Mount Diablo contractional step-over 216, earthquakes 422–3 microplate 148, 149 218 common near plate boundaries and Mid-Atlantic Ridge 97, 140, 148, 391 mountain belts other zones of deformation 103, alternative model of structure 125–6, collisional, intermediate and deep focus 422 127 earthquakes 93 intra-plate regions 422–3 hydrothermal vent fi elds 131 formation changes weathering rate at small magnitude, very common 422 magma supply focused at segment Earth’s surface 411 large tidal waves or tsunamis 422 centers 136, 138 mountain building, major episode in caused by earthquakes on faults possible model of structure beneath 125, Cenozoic 411–12 displacing ocean fl oor 253, 422 126 greatly increased physical and chemical eruptions of Santorini and segmentation 136 weathering 411 Krakatoa 422 fi rst order defi ned by transform Mt. Edgar Dome 356, 357 South Asia tsunami 422 faults 136 initial formation 358 Storega slide off Norway 422 second order defi ned by oblique offsets Mt. Edgar Shear Zone 357, 358 volcanic eruptions 423 of ridge axis 136 accommodates horizontal extension 359, devastating mudfl ows 423 third and fourth order 136 360 major, infrequent 423 seismic refraction experiments 125, 126 Murray Fracture Zone 119, 120 nature depends on chemistry of slow spreading rate 122, 122 different offsets 74, 89–90 magma 423 INDEX 475

nuées ardentes 423 Nusselt number (Nu), measures effi ciency of shallow structure of the axial region 141– quiet extrusion of low viscosity convection 387 2 magma 423 spreading rates and magma supply 141 natural remanent magnetization 65–6 obduction, of ophiolites 27–8, 342, 343 topography 122–3, 124 intensity in oceanic basalts larger than ocean basins FAMOUS study of a median rift induced magnetization 78 continued growth, contemporaneous valley 123, 123 magnetic cleaning technique, isolates mineralization at mid-ocean fast-spreading ridges 122, 122 CRM, TRM and DRM 65–6 ridge 413 gross morphology controlled by primary remanence 65 narrow, development of 413 separation rate 122 controls shapes of magnetic new mineral deposits at mid-ocean slow spreading ridges (axial volcanic lineations 78 ridge 413 ridges) 122–3, 122 detrital remanent magnetization ocean fl oor, dating of 84 ultraslow spreading rates 123, 124 (DRM) 65 ocean ridges 122–50 ocean trenches 7, 250–1, 264 igneous rocks, thermoremanent along-axis segmentation 133–40 depth magnetization (TRM) 65 adjacent segments, different mantle controlled by age of subducting secondary remanence, acquired sources 139 lithosphere 250 through subsequent history of along-axis variation of crustal reduced by subduction of aseismic rocks 65 structure 138, 139 ridges 251 chemical remanent magnetism formation of axial summit graben 138 large negative anomalies 252 (CRM) 65 magma supply focused at segment and underthrusting oceanic isothermal remanent magnetism centers 136, 138 lithosphere 250 (IRM) 65 ridge axis discontinuities 139 seismic activity on 252, 253, 254, 254 viscous remanent magnetism use of swath-mapping systems 133–4 ocean–continent convergence 287–302 (VRM) 65 asthenosphere occurs at shallow depth 49 central Andes 287–8, 288 Nazca plate, subduction under South broad structure of upper mantle conditions for orogenesis 297 America 281, 289, 294 below 125–7 mechanisms of noncollisional lithospheric tear may occur 290 crest adjustment 112, 112 orogenesis 297–302 three-dimensional view of P10.1, heat fl ow decreases to fl anking basins seismicity, plate motions and subduction 289–90 383 geometry 289–91 negative buoyancy force (FNB) 389, 389 heat fl ow and hydrothermal shortening and orogenesis in the backarc New Zealand circulation 129–31 environment 285 zone of deformation on Pacifi c plate 211, GDH1 model, predicted heat fl ow ocean–continent subduction zones 262, 263, 213, 239 values 129–30 264, 287 see also Southern Alps, New Zealand large variations in heat fl ux measured ocean–continent transition zone 193 Noril’sk deposit, Siberia 416 in young crust 125, 130 oceanic circulation and Earth’s climate, North America, western, suspect mark diverging plate boundaries 92 changes in 406–11 terranes 337 model of petrological processes occurring continental drift gave rise to major North American Cordillera at 142–4 changes 406, 407–8, 409 ACCRETE marine seismic transect across extended to incorporate a magma fi rst major build-up of ice in Coast belt 338, 339 chamber 145 Antarctica 409 accretion of Insular Superterrane 339 origin of anomalous upper mantle ocean basin confi guration affects Alexander and Wrangellia island arc beneath 127–8 transport of heat 406 terranes 339 petrology 140–1 oceanic core complexes 138 deformation of continental interior propagating rifts and microplates 145–8 oceanic crust 7, 24–7 339 initiation of ridge propagation, cause almost barren of radioactive isotopes 384 accretion of Intermontane Superterrane not known 148 changes in net rate of formation 405 337, 339 propagating rift model 145–7, 146 creation of 6, 106, 107 Baja–BC hypothesis 339 pseudofaults and failed rifts 146–7 extension of ridge crests, amagmatic distribution and dispersal of terranes ridge rotation model of spreading extension 138 336 center adjustment 145, 146 internal layering 21, 24–7 Southern Cordillera, structure where second rift propagation model, and in isostatic equilibrium with continental subduction occurs 338, 340 microplates 147–8 crust 24 see also Canadian Cordillera seawater circulation lateral motion 7 North Atlantic through crust controls heat fl ow layer 1 24–5 acoustic stratigraphy 25, 26 pattern 130–1 contourites 24 suggested examples of transform transports heat to surface 53 Pacifi c and Atlantic/Indian oceans 25 faults 89, 89 seismic evidence for axial magma progressively thickens away from ocean North Atlantic fracture zone, thin mafi c chamber 131–3 ridges 25 crust 149–50 shallow focus earthquake belt along layer 2 25, 142 North Atlantic igneous province 103 crest 93–4, 93 igneous origin proved 25 476 INDEX

oceanic crust (cont’d) oldest unequivocal examples Early Pacifi c Ocean model for confi rmed by seismic Proterozoic 369 central 394, 395 studies 143, 143 preserve ancient ocean fragments 208 northeastern, sea fl oor spreading around sublayers 26, 143 ophiolites 27–8, 30, 314–15, 361 pole of rotation 111, 112 layer 3 26–7, 131 assemblages in Precambrian oceanic plates reducing in size 96–7 concept of predominantly gabbroic orogens 368–9 Pacifi c rim, higher than average velocities layer 27 complete ophiolite sequence 27, 27 beneath 393 gabbroic 144, 145 correlation with oceanic lithosphere 27 Pacifi c–Farallon plate boundary 147 represents plutonic foundation of more than one type 28 paired metamorphic belts concept 277–8, oceanic crust 26 obduction 27, 343 278 sublayers 26, 27 many different mechanisms interpretations attempted 279, 280 “sealing age” 131 proposed 28 three pairs identifi ed in Japan 278, 278 structure 24 may have occurred soon after infer direction of past subduction and velocity structure, comparison of creation 28 plate motions 278–9, 279 investigations 24, 25 models of vary 342 paleobotany, shows pattern of continental oceanic crust, metamorphism of 28–9 oldest unequivocal examples Early fragmentation 63 hydrothermal circulation Proterozoic 368–9 paleoclimatology 60–1 must modify chemistry of ocean possible formation, forearc setting 28 continental reconstructions 61, 62 crust 28 in terms of sea fl oor spreading 144 latitude major controlling factor of responsible for formation of important usually occur in collisional orogens 27 climate 60 ore deposits 28 orogenesis 287 paleolatitude indicators, important 61 hydrothermal metamorphism, giving rise arc–continent colllision, mechanisms paleomagnetism 64–71 to greenschist facies of 330–2 apparent polar wander curves 67–8 assemblages 28–9, 29 continental collision, mechanisms natural remanent magnetism 65–6 seawater circulation occurs in upper part of 318–30 paleogeographic reconstructions based of crust 29 continental underthrusting 319 on 68, 71, 407–8 oceanic crust, origin of 142–5 indentation, lateral escape, and past and present geomagnetic fi eld 66–7 model, petrological processes occurring at gravitational collapse 319–26 rock magnetism 64–5 ocean ridges 142–4 lower crustal fl ow and ductile paleopoles 66–7 buoyant ascent of hot asthenospheric extrusion 326–30 determination of location of 370 material 142 noncollisional, mechanisms of 297 Paleotethys Ocean, opening of 377, 377 oceanic lithosphere 290 interplate coupling at the trench 297, Paleozoic passive margin sequence, western base marked by strong decrease in shear 298 USA 165, 166 wave velocity 349 structure and rheology of the Panama Isthmus, formation and behaves as a single rigid plate 39, 40 continental plate 299 intensifi cation of Gulf Stream 409 creation of, formation of ore bodies orogenic belts 92, 287–345 Pangea 3, 5, 370, 378, 401 within 415, 416 orogenic plateaux, and very weak crust 296, fi nal assembly of 377–8, 378 depth of low velocity zone (LVZ) 49, 50, 316–18 fragmentation 50 orogenic processes, noncollisional, accompanied by closure of oceans and depth–age relationship 128–9, 151 important boundary conditions, collisions 307, 331, 378, 378 cooling and contraction, half space, Andes 288, 288 and adaptive radiation of reptiles plate and GDH1 models 129, 130 orogens 63–4 elastic thickness 50 accretionary 287, 309, 336–42 expanding Earth hypothesis 381 formation of layer 3 by crystallization of ancient 287 heterogeneous 378 magma chamber(s) 27 Andean-type (non-collisional) 277, 287 progressively rifting apart 406, 407–8, layering confi rmed by sampling on collisional 287 409 Vema Fracture Zone 27 overlapping spreading centers (OSCs) Cenozoic, Africa, India and Australia models 134–5 drifted north 409 for formation of 131 possible evolutionary sequence 135 early Cretaceous, Antarctica–Africa

for mineralization in 416, 417 overriding plate resistance (RO) 389, 389 separation 407, 409 oceans oxygen isotope values, coincident with Early Triassic, possible surface ocean dispersal barriers to certain animals 62–3 Eocene–Oligocene boundary 409, current pattern 406, 407 heat fl ow decreases from ocean ridge to 410 late Jurassic, “Tethyan Embayment” fl anking basin 383 extended to west 406, 407, 409 Okinawa Trough 417 P waves 10 mid-Cretaceous, North and South Ontong Java Plateau 171, 171, 172 arrive before S waves 11 Atlantic gateway open 408, 409 ophiolite complexes 143 fi rst seismic arrivals mid-Oligocene, Southern Ocean circled

economic deposits of chromite in at greater distance Pn 19 Antarctica 408, 409

plutonic areas 416 within 200 km Pg 19 paramagnetic minerals 64–5 massive sulfi de complexes in 415–16, 416 in low velocity zone 21 ferro-magnetic substances 65 INDEX 477

Parana Flood Basalts 101, 101 plate motions, fi nite 110–13 ridge resistance RR 388 partial melting 128, 140, 173, 202, 355, 416 Euler poles, jump to new location 110, relative movement takes place on beneath arcs, driven by water 272–3 111, 112 asthenosphere 49 fractional crystallization, assimilation, sea fl oor spreading, pole of rotation plumes 399–400 magma mixing 173–4 jumps 110, 111, 112 plume hypothesis controversial 399 high-degree 351 the three plate problem 110, 110 primary 101, 399–400 low degree can increase alkalinity away plate motions, relative 94–7, 228, 234, 306–9 and rise in sea level 405 from trench 271 changes in direction, adjustment of secondary 400 and low velocity zones beneath rifts 160– transform faults and ocean see also mantle plumes; superplumes 1 ridges 112 Poisson’s ratio 24, 26, 154, 159 magma differentiation as melt moves into convergent boundaries, determining polarity chrons 79, 80 crust 273 relative velocities 95 polarity reversals 67 and melt extraction, buoyancy and described making use of Euler’s porphyry copper chemical depletion 350 theorem 94 formed during continental collision 419 melt segregation from along grain determination of pole of relative motion in oceanic island arcs 419 boundaries 274–5 for two plates 94–5, 94 rare in Archean 419 transport of melts 274–5 direct measurements of 107–9 in subduction zones 416–17 of the upper mantle 127–8, 128 comparison of models REVEL and Precambrian heat fl ow 347–9 passive continental margins NUVEL-1A 109, 109 must have been greater than at and formation of coal 421 early determinations summarized 108 present 347 see also continental margins, rifted independent of plate tectonic possible heat loss mechanisms 348 peridotite 350 models 109 Precambrian reconstruction, controversial high-degree partial melting of 351 older methods 107 and fl uid nature of 372 serpentinized 26, 138, 144 review using space geodesy Precambrian tectonic processes 347 perovskite 396 techniques 109 differences in inferred mechanism of heat Peru–Chile trench 250, 289 satellite laser ranging (SLR) 108 loss 348–9 seismicity nearly equal, fl at and steep slab satellite radio positioning conventional view 348–9 segments 297 technique 108 more recent view 349 shallow dip of Benioff zone 262 very long baseline interferometry propagating rifts 134, 135 strength of inter-plate coupling 297 (VLBI) 108 and microplates 145–8 summary of downdip stresses in Benioff global plate motions, more detailed Proterozoic Eon 347 zones 259, 260 analyses 95–6, 96 Proterozoic tectonics 361–9 Phanerozoic tectonic processes 363 additional plate boundaries recognized continental growth and craton phosphorites 61 95 stabilization 363–4 Pilbara craton, Australia measured using space geodesy 94 episodic crustal production, short differences between Eastern and Western Pacifi c and North American plates 211, pulses 363–4, 363 parts 356, 361 212, 233–6 growth by magma addition and terrane Hamersley Basin 365, 368 prediction of directions/rates of accretion 364 rocks refl ect Precambrian spreading/subduction 84, 96–7, 96 many uncertainties remain 369 stabilization 361 and surface velocity speeds 233–6 plate tectonics 364–9 see also Eastern Pilbara craton, Australia plate tectonic mechanisms, early occurrence pull-apart basins 211, 232, 320, 320 plate boundaries 93 of 347 Dagg Basin 220, 221 trenches 92 plate tectonics 8 Río Lempa pull-apart basin 215, 217 unstable 113, 113 driving mechanism of 390–3 Purtuniq Complex (ophiolites), Trans- see also ocean ridges; transform faults edge-force mechanism/model 391–3, Hudson orogen 369 plate confi gurations, reconstructions of 84, 391 push-ups, formed where intervening region 86 mantle drag mechanism/model 390, 391 compressed 211 plate margins implications of 405–27 accretive/constructive 84, 92, 112, 122, economic geology 412–22 Q zones 254 264 environmental change 405–12 Q-factor 254 destructive 92, 94, 112 natural hazards 422–3 Qinling suture, coincides with rheologically plate motions, absolute 97–9, 98 mechanism of 380–403 weak crustal corridor 327 defi ned in terms of NNR criterion by Proterozoic 364–9 Queen Charlotte Fault 338, 339 space geodesists 98, 154 early tectonic models 362, 364–5 model using hotspot information plates 7, 92 radioactive isotopes 383–4 98, 98 determining past relative positions 112 decay produces terrestrial heat 347

other frames of reference not forces acting on 388–90 Rayleigh number(Ra), defi ned 386–7 pursued 98–9 at subduction zones 389, 389 Rayleigh waves 10, 11, 18 should specify lithosphere motion relative mantle drag force 389, 389 Red Sea, hot brine pools 419

to lower mantle 97–8 ridge push force FRP 388, 389 and zinc-copper-lead sediments 413, 415 478 INDEX

red-beds 61 rifted volcanic margins 193–6 displacement on fault mainly strike- overlain by disseminated ores 413 components of 193 slip 163, 226 remnant arcs, subsidence of 280 high velocity lower crust, helps to evolution of 119, 120 Reunion Island hotspot 101, 101 dissipate thermal anomaly 193, 194, fault formed in heterogeneous may have moved north 102 195 lithosphere 226 Reykjanes Ridge Lofoten–Vesterålen continental joins Mendocino Triple Junction with larger volume of ductile crust 145 margin 193, 194, 195 Gulf of California 212, 226 slow-spreading ridge, process of main seismic facies of extrusive locking depths 238 accretion 133 units 193, 196, 196 relative motion between Pacifi c and study centered on magmatically active origin of enhanced igneous activity North American plates 233–6 axial volcanic ridge 133 uncertain 196 accommodation by dextral slip 233 Reynolds number (Re), defi ned 387 wedges of seaward-dipping refl ectors 193 aseismic creep between locked Rheic Ocean 376, 377 rifting segments 233 rheology, defi ned 33 magma-assisted 192–3 transfer of motion east of Sierra Rhine Graben 153, 153 isostatic elevation 192, 192 Nevada 234, 236 ridge propagation 90 thermal model 192 San Bernadino segment 238

ridge push force FRP 388, 389, 392 see also narrow rifts; wide rifts segments, differing short-term mechanical

ridge resistance RR 388 rifts behaviors 233 ridge–axis discontinuities 135, 137 active, variability of 153 strain accommodation 233 rift initiation 176–8 can accommodate extension without time and method of formation 119, 224, and deviatoric tensional stress crustal thinning 192 226 176, 177 comparison of mantle structure velocity model indicates relatively low infl uence of pre-existing lithospheric beneath 176 seismic velocities 226–7 weaknesses 177–8 ductile shear zones 185 San Andreas Fault Observatory at Depth and mechanism available to accommodate half-width 189, 190 (SAFOD) drilling program 247, 248 tension 176–7 lithospheric stretching in 179–81 San Francisco Bay area lithospheric separation by diking 177, low velocity zones beneath 160–1 contractional step-overs 177 mantle upwelling beneath 175–6 crustal shortening and topographic rift rocks, petrogenesis of 172–5 upwelling sublithospheric mantle 200 uplift related to 215–16 defi ning systematic compositional trends represent initial stage of continental vertical crust motion associated diffi cult 175 breakup 153 with 216, 218 generation of lithospheric melts strain localization in faults and shear Mission Hills step-over 216 common 174 zones, variability in 185 sea fl oor spreading 64, 73–84, 110, 111, 112, mafi c magmas may be affected by partial tectonically active 153 200, 406 melting 173–4 Rodinia 370–3, 371 concept conceived, mechanism mantle melting to produce basaltic beginning of assembly 372 proposed 6–7, 7 liquids 173, 174 break up 371, 372 and continental drift 77–8 rift basalts 172, 174 effect of dispersal on past climates 372–3 dating the ocean fl oor 84 trace elements and isotopic large-scale magmatic events during direction not always constant 145 characteristics 173, 174 assembly 403 geomagnetic reversals 74–7 rift to rifted margin transition 202–6 Torsvik reconstruction 372, 373 magnetic surveying method 73 East African Rift system 202–3 Romanche Fracture Zone 231, 231 magnetostratigraphy 79–84 Woodlark Rift 204–6, 207 iron sulfi de concretions reported marine magnetic anomalies 73–4 rifted continental margins 239, 241 from 419 registers history of reversals of Earth’s rifted margins, evolution of 198–202 magnetic fi eld (theory) 7 magma accretion, mantle exhumation S waves 10–11 and rise in sea level 405 and detachment faulting 200–2 in low velocity zone 21 spreading rates varying with time 83, 83 post-rift subsidence and stretching 198– sagduction models 358 symmetry about ridge axis 143 200 San Andreas Fault, California 224, 226–8 Vine–Matthews hypothesis 76–9 amount of subsidence related to attempts to directly evaluate strength verifi cation of 79, 81 magnitude of stretching factor of 246, 247, 248 sea level (β) 198–9 Big Bend region, strike-slip partitioned major change during ice ages 405 investigation of lithospheric-scale system 223 marine transgression and regression due stretching factors 199 creeping vs. locked segments 246, 248 to change in 405 transition to sea fl oor spreading 200 possibly locally reorienting regional worldwide increase, due to Cretaceous rifted non-volcanic margins 196–8, 197 stresses 246 Superplume 106, 107, 405 continentward-dipping refl ectors 196 resolution of problems, independent seawater chemistry, changes in 8, may contain areas of exhumed measurements needed 248 405–6

serpentinized upper mantle 196 direct measurement of relative plate due to variations of pCO2 in the air 406 two end-member types 196, 197, 198 motion, early methods 108 variation in the Mg/Ca ratio 405–6, 405 INDEX 479

sediment subduction and subduction collision of Fort Simpson terrane 365 southeast Greenland volcanic margin 200 erosion 264 Hottah terrane formed as a magmatic southern Africa 394, 395 sedimentary basin deposits 420–1 arc 365 Southern Alps, New Zealand 287, 306, 327 fossil fuels found in 420–1 collision with craton 365, 367 exhumation of deep crustal rocks on principal criteria for development of P-wave velocity model, Hottah and Fort southeast side 243, 243 petroleum and gas 420–1 Simpson terranes 367 model predictions match many observed migration to oil traps 420 slow-spreading ridges 122–3, 122, 139, patterns 243, 244 preservation of kerogens 420 201–2 Southern Ocean, opened up 408, 409 tectonic control of reservoir alternate phases of volcanic and tectonic species diversity, controlled by continental location 420 extension 141 drift 63–4, 64 sedimentary basins, compressional 302–5 axial volcanic ridges, inner valley step-overs 211, 215–16, 216, 234 basin inversion 302, 303 fl oor 141 characterized by pull-apart basins 211 seismic anisotropy 41–2, 227–8 bounding faults 141 El Salvador Fault Zone 214–15, 217 in D′′ layer 41, 394 complex magma chambers 140 Stillwater complex 363 mantle measurements yield information extension by normal faulting 141 strain 34 on pattern of fl ow 394 lower rate of magma supply 141 strain and brittle deformation 34–6 studies in upper mantle 394 model for 133, 134 strain and ductile deformation 36–7 seismic tomography 17–19, 126, 393–4 ultra-slow 123, 124, 142 strain and earthquakes 10–12 actual travel times of P and S waves see also Gakkel Ridge see also deformation used 17 upper brittle layer deforms by strain, localization and delocalization areas underlain by anomalously low necking 145 mechanisms 239–46 velocity mantle 393 very slow 144 lithospheric heterogeneity 239–41 cross sections through shear wave velocity axial volcanic ridges 142 strain-softening feedbacks 242–6 model 394 magmatic segments 141–2 strain, localization and delocalization global methods wider zone of crustal accretion 144 processes great circle method 19, 19 see also Mid-Atlantic Ridge; Reykjanes along transforms and large strike-slip single station confi guration 19 Ridge faults 239 local methods South Africa buoyancy forces and lower crustal local inversion method 18–19, 18 broad low velocity zone imaged in deep fl ow 181–3 teleseismic method 18, 18 mantle 176 during extension 178–9 normal procedure 18 superswell 394, 400 during shortening and convergence 287, provides information on 3-D mantle several potential primary plumes near 302–3, 322, 326–7, 344 structure 393 99, 397, 400 kinematic modeling 157, 163, 164, 178 surface waves, procedure more South America of continental extension 178, 178 complex 17–18 Andean orogen 287–302 lithospheric fl exure 183–4 used in investigation of the Tonga early Mesozoic extensional and backarc lithospheric heterogeneity 239–41 arc 254, 255 basins 284, 285 lithospheric stretching 179–81 seismic waves 10–11 most occur without formation of magma-assisted rifting 192–3 body waves 10–11 basaltic basin fl oor 285 mechanical models 178 propagate by elastic deformation 10 possible modern analogue, Bransfi eld rheological stratifi cation of the surface waves 11 basin 250, 285 lithosphere 188–92 seismic zones, double, in subduction earthquake focal mechanism strain hardening mechanisms 178 zones 257 solutions 289, 290 strain-induced weakening 184–8 serpentine mud volcanoes 265, 277 rifted from Africa 409 strain-softening feedbacks 242–6 serpentinite 149 South American plate, tectonic strain softening production of 265, 273 domains 297, 298, 299 crust and mantle, can produce large-offset sedimentary, occurs in blueschist facies backarc-foreland domain shear zones 176, 187 metamorphic belts 277 block rotations 294, 299 frictional-plastic (brittle) 186, 187 serpentinization 340 control of deformation 297 and viscous weakening, mechanisms Sevier thrust belt 165, 166 rheology of continental plate 297 combined 186, 187 Siberian fl ood basalts 171 variations in strength of inter-plate strain softening effects, continental Sichuan basin coupling 297 underthrusting 327 topography to northwest anomalously forearc domain 297, 298, 299 strain-softening feedbacks 242–6, 327 high 327 coupling across ocean–continent exhumation of deep crustal rocks 242, virtually undeformed 316 interface 297 243–4 slab resistance (RS) 389, 389 results of modeling 298, 299 increased pore fl uid pressure 242–3 slab-pull forces FSP 392, 401 South Atlantic, rate of sea fl oor positive feedbacks 242–6 acting on subducting plate 275, 389, 389 spreading 83, 84 stratigraphic sections, correlation between Slave craton, fi nal assembly 365, 365 South Pacifi c Superswell 128, 394 Gondwana continents 59, 60 creation of Great Bear Magmatic arc 365 hotspots on 400 marker beds 59, 60 480 INDEX

strike-slip displacement, accommodated ensialic backarc basins, vein-type gold/ differences between African and relative motion, N America accreted silver deposits 418 Pacifi c 400 terranes 339 Kuroko-type massive sulfi des 417, 418 downwellings produce depressed strike-slip duplexes, explained 216, 220 porphyry coppers, uniformity of crust 395 strike-slip faulting, and terrane worldwide 416–17 syntaxis 310, 316 dispersal 340 sediment subduction and subduction strike-slip fault styles and erosion 264 Taconic Orogeny 376 physiography 211–24 shallow dips Taiwan, oblique arc–continent collision 330, linear fault scarps and laterally offset restrict fl ow of asthenosphere in 332, 333 surface features 211 mantle wedge 262 four stages proposed 332, 333, 334 releasing and restraining bends 216, 217, strong coupling with overriding processes in initial stage 332, 334 219, 220, 221, 222 plate 256, 262 progressive younging of collision step-overs, push-ups and pull-apart two end-member types zone 330, 332, 333 basins 211, 214–17, 216, 218, 234 recognized 262, 263 rapid progress from initial to advanced transtension and transpression 214 speed of downgoing slab 389 stage suggested 332 strike-slip duplexes, fans and fl ower structure of from earthquakes 252–9 Tarim Basin 322, 324, 326 structures 220, 222–3, 222 trench parallel component 97 Taylor number (T), defi ned 387 strike-slip partitioning in transpression variations in characteristics 262–4 tectonic processes and transtension 213, 219, 221, 223 accretionary or erosive 264 Phanerozoic 363 strike-slip faults Chilean type 262, 263, 297 Precambrian 347, 348–9 large continental 211 Mariana type 262, 263, 297 tectonic underplating 266, 267 large-scale 86, 88, 246–8 supercontinent cycle 370–8 temperature, controlling strength of fans/horsetail splays may form at earlier supercontinents 373–4 subsurface materials 49–50 ends 216, 222–3 collisional assembly of Columbia 374, terrane accretion and continental multiple segments and step-overs 211, 375 growth 287, 332–45, 364, 418–19 216 Kenorland (single continent) 373, 374 structure of accretionary orogens 336–42 negative or positive fl ower many supercratons 373–4, 374 terrane accretion, mechanisms of 342–5 structures 222, 223 Nuna 374 growth by magmatism and releasing and restraining bends 216, 217, Gondwana–Pangea assembly and sedimentation 342 220 dispersal 374–8 Lachlan orogen 342, 343, 344, 344 tendency to diverge and converge 220, amalgamation of East and West growth by obduction of ophiolites 342 222 Gondwana 374 Coast Range Ophiolite 342, 343 trench parallel 97 formation of West Gondwana 371, 374 origination of exotic terranes 342, 376 subduction Pannotia 374, 375, 376 processes similar to those in modern high velocities associated with 394 initiation and termination of subduction orogens 342 Late Archean, of entire crust 355, 355 zones 398 terrane analysis 332–6 subduction zones 8, 250–85, 376 a late Proterozoic supercontinent 370–3 chronological sequence of accretion 336, beneath central Andes 289, 291 fragmentation of 372 336 blueschist to eclogite facies SWEAT hypothesis 370, 372 criteria for distinguishing identity of transformation 275, 276, 281 mechanism of 401–3 separate terranes 335 characterized as accretionary or continental collision at site of terrane recognition 335 erosive 250, 264, 265 downwelling 401, 402 terranes Early Proterozoic 365 internal heating and episodic plate boundaries of 332, 335 elusive route of return fl ow to mid-ocean motion reversals 401 collage of fault-bound blocks 332 ridges 397 mantle convection cells 396–8, 401 exotic factors controlling response of upper mechanisms promoting growth and Cuyania to Gondwana 375, 377 plate to compression 297–302 dispersal 401 to Laurentia 376–7 forces acting on plates two types of mantle plume events 403 exotic or native 332

bending resistance (RB) 389, 389 pre-Mesozoic reconstructions 370 analytical tools for determination

negative buoyancy force (FNB) 389, 389 methods of quantifying plate of 336

overriding plate resistance (RO) 389, 389 motions 370 general types 335–6

slab resistance (RS) 389, 389 tensile stresses in supercontinent native to Laurentia 376

slab-pull force FSP 389, 389 interiors 401, 403 nonturbiditic clastic, carbonate or fossil 352, 353 superplumes 33, 106–7 evaporite sedimentary 335 gravity anomalies of 252, 253 rise from D″ layer 106 suspect 335, 337 location of fundamental 396 superswells 394–5 tectonic and sedimentary mélange oceanic, several forms of mineralization correlate with anomalously high elevation terranes 335 present 416–18 of Earth’s surface 394 terrestrial heat fl ow 51–3 Andean subduction, specifi c types of dynamically supported by hot geothermal energy 51 deposit 417–18 upwellings 394–5 and radioactive decay 52 INDEX 481

heat fl ow values 53 transtension beneath major hotspots, superswells and measurements on land 52–3 in second propagating rift model 147 inferred upwellings 395, 396 measurements at sea 3 Transverse Ranges, S. California D′′ layer, development of peaks focused other energy sources 51–2 earthquake focal mechanisms show into narrow conduits 399 tetrapods, past distribution 62 thrust solutions on fault splays 219, underthrusting 294, 297–306, 315, 319, 389 thermal energy, driving lithospheric 220 upper crust plates 390–3 restraining bend, San Andreas Fault 212, continental crust 23, 383–4 thermomechanical models 219, 220 simple structure at crests of fast-spreading control width of the deforming zone 241 San Gabriel Mountains ridges 141, 142 involving channel fl ow and ductile fractures/fl uids penetrated along upper mantle extrusion 327–8, 329, 330 décollement anomalous, origin of beneath ocean Himalayan–Tibetan orogen, results surface 227 ridges 127–8 for 328, 329 shear wave (SKS) splitting partial melting 127–8, 128 initial thermal structure 328, 329 measurements show anisotropic phase change unlikely to contribute to position of suture (S) 328, 329 upper mantle 228 uplift 127 provenance of channel fl ow seismic anisotropy, study of structure of possible sources of low-density material 328, 330 subcontinental mantle 227–8 regions 127–8 strain localizes where lithospheric slip on San Andreas fault slower 234 broad structure below ocean ridges 125–7 strength is at minimum 241 thick crustal root below surface trace of ambiguity inherent in gravity strike-slip faulting in three-layer San Andreas Fault 226, 227, 227 modeling 126–7, 126, 127

lithosphere 239, 240, 241 trench suction force (FSU) 392, 401 free air anomalies broadly zero 125, tholeiites 140, 172–3, 175 possible causes 389–90, 390 125, 126 tholeiitic magma series 271 roll-back 282, 284, 389 isostatic compensation by Pratt-type above young subduction zones 271 trilobites, Cambrian, oceanic dispersal mechanism 125 Tibetan Plateau, elevation of 411–12 barriers 62–3 probably peridotitic 31 current uplift models imply sudden fi nal triple junctions Ural orogen, formation of 378 uplift 412 present day 120 USA greatly intensifi ed southwest stability of 113–20 southwestern, strain localization in 163, monsoon 411, 412 evolution of unstable to stable 212, 241 Timor–Banda arc region, early stage arc– junction 115–16, 117 western continent collision 330 geometry/stability, all possible triple Paleozoic passive margin Tintina Fault, major lithospheric junctions 118, 118, 120 sequence 165, 166 structure 339 transform boundary 114, 115 plate-tectonic style of tonalites 273, 350 trench boundary 114, 114 deformation 238–9 Tonga trench, roll-back of Pacifi c slab trondhjemites 350 see also Basin and Range Province; beneath 282, 284 see also TTG (tonalite-trondhjemite- California; North American Tonga–Kermadec island arc system granodiorite) suites Cordillera; San Andreas Fault earthquakes 253, 254 Troodos ophiolite, Cyprus 144 differences in amplitude described in mineralization in 416 velocity fi elds, modeled 236–9 terms of the Q factor 254, 254 tropical rain forests 411 block rotation models 237–9 Tonga–Kermadec trench 250 need high temperatures and much continuum model approach 235, 236–7 lithospheric bending 255, 256 precipitation 409–10 mismatches between geodetic and transfer zones 155, 158 present day extensive areas 410 geologic slip rates 237 transform continental margins 230–2 true polar wander 102, 103–6, 398 Vema Fracture Zone 149 transform fault resistance 390 analysis of Pacifi c Plate using viscous fl ow 186, 187 transform faults 84–90, 92, 112, 145, 206 paleomagnetic poles 105 volcanic activity 8, 169–76 as fi rst order segment boundaries 136, investigative method 104 large igneous provinces (LIPs) 169–72 138 and mantle fl ow 106 mantle upwelling beneath rifts 175–6 nonrigid 135 path for past 200 Ma 104–5, 105 petrogenesis of rift rocks 172–5 oceanic, favorable environments for shifting of lithosphere and mantle as volcanic and plutonic activity 271–5 mineralization 419 single unit during 106 origin of magmas supplying ridge jumps and transform fault TTG (tonalite-trondhjemite-granodiorite) complexes 272 offsets 89–90 suites 350, 354–5, 362 incorporation of trench sediments 272 ridge–ridge transform faults 88–9 emplacement of hot granitoids into older types of rock in supra-subduction transformational/anticrack faulting 258 greenstones 358, 359 zones 271 transforms convective overturn 358, 359 volcanogenic massive sulfi de (VMS) continental 92 turbidite terranes 335 deposits 417, 418 measuring the strength of 246–8 transpression 147 ultra-low velocity zones (ULVZ) 395, 396, Walker Lane 163, 164, 212, 234, 237 and transtension 213, 214, 219, 221, 223 396 southern 242 482 INDEX

weakening, strain-induced 186, 187 delocalized strain 153, 165 rift initiation in the Pliocene 206 can be suppressed by other heterogeneous crustal thinning in Wopmay orogen, growth by addition of mechanisms 188 previously thickened crust 165–6, magmatic arcs 365, 366 effect sensitive to rift velocity 186, 188 166 World Wide Standardized Seismograph formation of large-offset normal faults, small- and large-magnitude normal Network (1961) 11, 93 parameter dependent 185 faulting 167, 168–9, 170 Wrangellia terrane, distinctive geology, well reduction of cohesion during thin mantle lithosphere and anomalously studied 339 extension 185 high heat fl ow 168 WW2, prior to, geological study of land weathering Wilson Cycle 208–9, 365, 369 areas only 5 of carbonates by carbonic acid 411 continent–continent collision 209 of silicate rocks expanding and contracting oceans 209 xenoliths 22, 30 by carbonic acid 411 many cycles of ocean creation and mantle enhanced in late Miocene, removal of destruction 58, 59, 208–9 Archean roots buoyant, depleted in CO from atmosphere 412 stages in 208, 209 2 incompatible elements 350 Wegener, A. 8 Woodlark Rift 204–6, 207, 280, 285 cool cratonic roots soon reached Die Entstehung der Kontinente und continental break-up current thickness 348 Ozeane 5 present focus, asymmetrical rift basin oldest melting events, Early–Middle Permo-Carboniferous glaciation 3 near Moresby Seamount 206 Archean 351 pioneer of theory of continental drift 3 step-wise formation of 206, 207 Re-Os isotope analyses give age of melt theory based on data from several continental rifting in Papuan Peninsula extraction 351 disciplines 5 204, 205, 206 reconstruction of the continents 3, 4 continuum of active extensional uniformitarian concept of drift 3 processes 204 zircon wide rifts, general characteristics 162–9 development of strain localization and sea comparison of age spectra from detrital broadly distributed deformation 162–5, fl oor spreading 206 zircon populations 336 162, 163, 164 formation of core complexes 206 detrital zircon minerals, Yilgarn craton, and crustal buoyancy forces 181, 182 pre-rift evolution 206 W Australia 347