Deep Drilling Results in the Atlantic Ocean: Ocean Crust

Title Page......Page 3
Copyright......Page 4
Preface......Page 5
Contents......Page 6
Introduction......Page 8
Models With a Layered Crust......Page 9
Models with Velocity Gradients......Page 10
Evidence from Reflection Seismology......Page 11
Summary......Page 16
References......Page 19
Introduction......Page 22
GLORIA Survey Operations and Interpretation......Page 23
Mid-Atlantic Ridge Study Areas......Page 28
b Kurchatov Fracture Zone......Page 29
c 45 North Area......Page 31
a Ratio of inward to outward facing faults......Page 32
c Fault Spacing......Page 34
Geometry of Fault Generation on Moving Lithosphere......Page 35
Conclusions......Page 37
Acknowledgements......Page 38
Width of the Zone of Extrusion......Page 40
Volcanoes in the Vertical Section......Page 43
Surface Debris......Page 44
Fault Shearing and Gouge......Page 45
Typical Crust Versus Fracture Zone Crust......Page 46
Summary and Conclusions......Page 47
References......Page 48
Location of drillholes with regard to geology......Page 50
Reykjanes high-temperature area loc. 15......Page 54
Krafla high-temperature area......Page 55
Reykir low-temperature area......Page 56
Geophysical logging......Page 57
Chlorine variations......Page 58
Mineral/solute equilibria......Page 59
Rock alteration......Page 62
Correlation of rock alteration with temperature in active geothermal systems......Page 64
Remanence......Page 66
Susceptibility......Page 67
Heat flow......Page 68
The location of the drillholes is shown in Fig.1.......Page 69
References......Page 70
Regional Horpho-Tectonic Setting......Page 73
The Cayman Trough Project......Page 74
The Inner Floor......Page 77
The Rift Valley Walls......Page 81
Rocks From the Mid-Cayman Rise Spreading Center......Page 83
Petrology of Basalts from the Inner Floor......Page 84
Petrology of Gabbros from the Rift Valley Walls......Page 89
Petrology of Ultramafic Rocks from the Rift Valley Walls......Page 94
Magnetic Properties of Gabbros from the Rift Valley Walls......Page 95
Summary and Conclusions......Page 98
References......Page 99
Introduction......Page 101
Porosity......Page 105
Seismic Velocities......Page 106
Relations Between Velocity and Other Parameters......Page 107
Mean Elastic Parameters For Drilled Sections......Page 110
Resistivity as a Function of Pressure......Page 112
Resistivity as a Function of Temperature......Page 113
Mean Resistivities for Drilled Sections......Page 114
Thermal Conductivity......Page 115
Conclusions......Page 116
References......Page 117
The Physical State of the Upper Levels of Cretaceous Oceanic Crust from the Results of Logging, Laboratory Studies and the Oblique Seismic Experiment at Dsdp Sites 417 and 418......Page 120
Introduction......Page 121
Basement Lithology and Physical Properties......Page 123
Downhole Logging in Hole 4l7D......Page 127
The Oblique Seismic Experiment......Page 133
Data Comparison......Page 134
1 Composition......Page 135
5 Velocity vs. Depth......Page 138
6 Anisotropy......Page 139
References......Page 140
Geomagnetic Polarity......Page 142
The Cenozoic Reversal Sequence......Page 143
The Mesozoic Reversal Sequence......Page 144
The Magnetic Smooth Zones......Page 145
Cretaceous Spreading Rates......Page 146
Direction of Magnetization of Oceanic Basalts......Page 147
Oceanic Basalt Magnetic Mineralogy......Page 149
The Thickness of the Magnetic Anomaly Source Layer......Page 150
Ophiolites......Page 152
Multi-Layer Models of Magnetic Anomaly Sources......Page 153
Acknowledgements......Page 154
References......Page 155
Prevalent Models......Page 158
Final Distribution vs. Original Distribution, Figure 1......Page 159
Computer Simulation of the Magnetic Source Layer and Anomalies......Page 160
An Example, Figure 2......Page 161
Simulated Magnetic Source Layer, Figure 4......Page 162
Simulated Fast Spreading Anomalies, Figure 5......Page 163
Short Wavelength Information in Fast Spreading Anomalies, Figures 5 and 6......Page 164
Discussion and Conclusion......Page 165
References......Page 166
A. Gaussian Spatial Distribution......Page 167
B. Poisson Temporal Distribution......Page 168
Results......Page 169
Appendix I. The Stretching Function......Page 170
References......Page 171
Evidence......Page 173
Implications and Weaknesses of the Model......Page 174
References......Page 175
Low Temperature Alteration of the Magnetic Minerals in Ocean Floor Basalts......Page 176
Introduction......Page 177
Microprobe analysis......Page 178
Opaque reinerals contained in ocean floor basalts......Page 179
Oxidation of titanomagnetite......Page 181
Ore microscopy of altered titano-magnetitesin ocean floor basalts......Page 185
Primary composition of titanomagnetites......Page 188
Mechanism of low temperature oxidation......Page 190
Correlation between Curie temperature and oxidation parameter z......Page 192
Variation of Curie temperature with age......Page 199
Variation of magnetization intensity......Page 201
Variation of magnetization direction with low temperature oxidation......Page 209
Conclusions......Page 213
References......Page 214
Introduction......Page 217
1. FAMOUS pillow basalts......Page 218
2. Leg 37 pillow basalts......Page 221
1. Magnetic effects of maghemitization: comparison of FAMOUS and Leg 37 pillow basalts.......Page 222
1. FAMOUS pillow basalts......Page 226
IV Conclusions......Page 228
References......Page 232
Characteristics of Ocean-Floor Metamorphics
......Page 236
Facies Nomenclature......Page 238
Congruence and Element Fluxes
......Page 239
Modelling Metamorphic Processes......Page 240
References......Page 242
Tectonic Emplacement of Crust in Oceanic Fracture Zones......Page 245
Igneous Emplacement of Crust in Oceanic Fracture Zones......Page 247
Structure of Oceanic Fracture Zones......Page 249
Igneous Emplacement of Crust in Fracture Zones......Page 252
References......Page 253
Comparison of Field Sampling Methods......Page 255
Regional Setting and Sampling Density......Page 260
Relations To Previous  Work on Basaltic Glasses from 0-37° N......Page 261
Petrogenesis......Page 263
Secular Variations......Page 265
Acknowledgements......Page 266
References......Page 267
Introduction......Page 268
The Nature of Primary Magmas......Page 269
The Clinopyroxene Problem......Page 272
The Magmaphile Element Problem......Page 273
Discussion......Page 275
References......Page 277
Introduction......Page 279
Compositional Variation in Layer 2......Page 280
Petrography and Mineralogy......Page 282
Stratigraphy of Layer 2......Page 284
Chemical Variations in Space and Time......Page 286
Conclusions and Suggestions for Future Drilling......Page 287
References......Page 288
Introduction......Page 291
Mid-atlantic Ridge 63° N: Sites 407, 408 and 409
......Page 293
Mid-Atlantic Ridge 45°  N: Site 410
......Page 296
Mid-Atlantic Ridge 36°n: Sites 411, 412 and 413 Famous Area 
......Page 297
Variables Controlling Basalt Compositions......Page 300
Regional Comparisons......Page 301
Nature and Causes of Regiqnal Heterogeneities
......Page 302
Conclusions......Page 304
References......Page 305
Introduction......Page 308
Conclusions......Page 316
References......Page 319
Introduction......Page 320
Lithology and Eruptive Chronology......Page 321
Chemical Variation of Basalts......Page 322
Lithology and Magnetic Stratigraphy......Page 323
Chemical Variation of Igneous Rocks......Page 326
Synthesis of Ocean Ridge Processes......Page 330
References......Page 335
Introduction......Page 337
Compositional Variations in Mid-Ocean Ridge Basalts and Basaltic Glasses......Page 338
Crystal Fractionation-at Low Pressures......Page 340
Fractionation at High Pressures......Page 342
Magma Mixing......Page 344
Conclusions......Page 345
References......Page 346
Introduction......Page 348
Review of Sr, Nd and Pb- Isotope Geochemistry......Page 349
Differentiation and Evolution of Mantle Magma Sources......Page 351
Dynamical Processes in the Mantle......Page 353
Concluding Remarks......Page 354
References......Page 355
Introduction......Page 358
Alteration Process. Alkali Metals and Strontium
......Page 359
Partition Coefficients and Physico-Chemical Properties of Trace Elements 
......Page 361
Mantle Hemogeneity or Heteogeneity : Y/tb, Zr/hf, Nb/ta, La And Th. A Comparision with Chondrites And Lunar Samples
......Page 365
Partial Melting and Magma Mixing
......Page 368
Co, Ni, Cr : Fractional Crystallization Process......Page 370
References......Page 373
Introduction......Page 375
Character of Site 417 Basalts......Page 376
Chemistry of the Altered Basalts of 4l7A......Page 377
Evaluation of Elemental Fluxes - the Problem of Dredged vs Drilled Basalts......Page 384
Conclusions......Page 386
References......Page 387
Introduction......Page 389
The Galapagos Data......Page 390
The Carbonate System: At, EC02 , Ca......Page 392
Reduced Specie: H2s, Mn2+,  Fe2+......Page 394
References......Page 395
The Chemistry of the Vent Waters......Page 397
Composition of the Erupted Magmas......Page 398
A Conceptual Model for the Galapagos Rift Thermal Springs......Page 401
Extracted Heat and Available Heat......Page 402
The Heat Budget and Depth of Cooling of Hydrothermal Systems......Page 404
Depths of Penetration and Extraction......Page 405
Summary and Conclusions......Page 406
References......Page 407
Introduction......Page 409
Geologic Setting......Page 410
Results......Page 415
Discussion......Page 418
Conclusions......Page 431
References......Page 432
Ophiolitic Rocks and Evidence for Hydrothermal Convection of Sea Water Within Oceanic Crust......Page 435
References......Page 437