Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
- Keyword
-
- Marine geology and geophysics : midocean ridge processes (2)
- Ambient mantle temperatures (1)
- Asymmetric spreading (1)
- Atlantis II fracture zone (1)
- Compaction (1)
-
- Core complex (1)
- Extensional faulting (1)
- Geochronology (1)
- Granite (1)
- Integrated Ocean Drilling Program (1)
- Lower crust (1)
- Mantle plumes (1)
- Marine geology and geophysics : marine magnetics and paleomagnetics (1)
- Marine geology and geophysics : oce (1)
- Marine geology and geophysics : ocean drilling (1)
- Marine geology and geophysics : plate tectonics (1)
- Melt generation (1)
- Melt segregation (1)
- Mid ocean ridge basalt (1)
- Mineralogy and petrology : geochemical modeling (1)
- Mineralogy and petrology : magma genesis and partial melting (1)
- Mineralogy and petrology : mantle processes (1)
- Nonvolcanic mid-ocean ridges (1)
- Ocean drilling program (1)
- Oceanic crust (1)
- Petrology (1)
- Ridge segmentation (1)
- Seafloor spreading (1)
- Site U1309 (1)
- Slow (1)
Articles 1 - 7 of 7
Full-Text Articles in Physical Sciences and Mathematics
Cooling History Of Atlantis Bank Oceanic Core Complex: Evidence For Hydrothermal Activity 2.6 Ma Off Axis, J. J. Schwartz, Barbara John, Michael Cheadle, P. W. Reiners, A. G. Baines
Cooling History Of Atlantis Bank Oceanic Core Complex: Evidence For Hydrothermal Activity 2.6 Ma Off Axis, J. J. Schwartz, Barbara John, Michael Cheadle, P. W. Reiners, A. G. Baines
Michael Cheadle
We report 26 (U-Th)/He zircon ages from Atlantis Bank, Southwest Indian Ridge, which constrain time scales and rates of lower crustal cooling in ultraslow spreading oceanic crust in this setting. Samples from the detachment fault surface indicate that denuded oceanic crust cooled rapidly (< 1 Ma), yielding cooling rates > 1200 degrees C/Ma, consistent with existing models for the cooling of oceanic crust. (U-Th)/He zircon ages from samples collected along N-S and E-W trending faults scarps record young ages inconsistent with standard cooling models for lower oceanic crust. These samples have a mean (U-Th)/He zircon age 2.6 Ma younger than their corresponding igneous crystallization ages and …
Evolution Of The Southwest Indian Ridge From 55 Degrees 45 ' E To 62 Degrees E: Changes In Plate-Boundary Geometry Since 26 Ma, A. G. Baines, Michael Cheadle, H.J.B. Dick, A. H. Scheirer, Barbara John, N. J. Kusznir, T. Matsumoto
Evolution Of The Southwest Indian Ridge From 55 Degrees 45 ' E To 62 Degrees E: Changes In Plate-Boundary Geometry Since 26 Ma, A. G. Baines, Michael Cheadle, H.J.B. Dick, A. H. Scheirer, Barbara John, N. J. Kusznir, T. Matsumoto
Michael Cheadle
[1] From 55 degrees 45'E to 58 degrees 45'E and from 60 degrees 30'E to 62 degrees 00'E, the ultraslow-spreading Southwest Indian Ridge (SWIR) consists of magmatic spreading segments separated by oblique amagmatic spreading segments, transform faults, and nontransform discontinuities. Off-axis magnetic and multibeam bathymetric data permit investigation of the evolution of this part of the SWIR. Individual magmatic segments show varying magnitudes and directions of asymmetric spreading, which requires that the shape of the plate boundary has changed significantly over time. In particular, since 26 Ma the Atlantis II transform fault grew by 90 km to reach 199 km, …
Protracted Construction Of Gabbroic Crust At A Slow Spreading Ridge: Constraints From (206)Pb/(238)U Zircon Ages From Atlantis Massif And Iodp Hole U1309d (30 Degrees N, Mar), C. B. Grimes, Barbara John, Michael Cheadle, J. L. Wooden
Protracted Construction Of Gabbroic Crust At A Slow Spreading Ridge: Constraints From (206)Pb/(238)U Zircon Ages From Atlantis Massif And Iodp Hole U1309d (30 Degrees N, Mar), C. B. Grimes, Barbara John, Michael Cheadle, J. L. Wooden
Michael Cheadle
Sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon ages of 24 samples from oceanic crust recovered in Integrated Ocean Drilling Program (IODP) Hole U1309D and from the surface of Atlantis Massif, Mid-Atlantic Ridge (MAR) (30 degrees N) document a protracted history of accretion in the footwall to an oceanic detachment fault. Ages for 18 samples of evolved Fe-Ti oxide gabbro and felsic dikes collected 40-1415 m below seafloor in U1309D yield a weighted mean of 1.20 +/- 0.03 Ma (mean square of weighted deviates = 7.1). However, the ages range from 1.08 +/- 0.07 Ma and 1.28 +/- 0.05 Ma indicating …
Nonvolcanic Seafloor Spreading And Corner-Flow Rotation Accommodated By Extensional Faulting At 15 Degrees N On The Mid-Atlantic Ridge: A Structural Synthesis Of Odp Leg 209, T. Schroeder, H.J.B. Dick, U. Faul, J. F. Casey, P. B. Kelemen
Nonvolcanic Seafloor Spreading And Corner-Flow Rotation Accommodated By Extensional Faulting At 15 Degrees N On The Mid-Atlantic Ridge: A Structural Synthesis Of Odp Leg 209, T. Schroeder, H.J.B. Dick, U. Faul, J. F. Casey, P. B. Kelemen
Michael Cheadle
[1] Drilling during ODP Leg 209, dredging, and submersible dives have delineated an anomalous stretch of the Mid-Atlantic Ridge north and south of the 15 degrees 20'N Fracture Zone. The seafloor here consists dominantly of mantle peridotite with gabbroic intrusions that in places is covered by a thin, discontinuous extrusive volcanic layer. Thick lithosphere ( 10 - 20 km) in this region inhibits magma from reaching shallow levels beneath the ridge axis, thereby causing plate accretion to be accommodated by extensional faulting rather than magmatism. The bathymetry and complex fault relations in the drill-core suggest that mantle denudation and spreading …
Inherited Zircon And The Magmatic Construction Of Oceanic Crust, J. J. Schwartz, Barbara John, Michael Cheadle, C. Grimes, E. A. Miranda, J. L. Wooden, H.J.B. Dick
Inherited Zircon And The Magmatic Construction Of Oceanic Crust, J. J. Schwartz, Barbara John, Michael Cheadle, C. Grimes, E. A. Miranda, J. L. Wooden, H.J.B. Dick
Michael Cheadle
Meeting Abstract for “Inherited Zircon and the Magmatic Construction of Oceanic Crust,” Goldschmidt Conference Abstracts 2005, Geochronology of Tectonic Processes.
Quantitative Modeling Of Granitic Melt Generation And Segregation In The Continental Crust, M. D. Jackson, Michael Cheadle, M. P. Atherton
Quantitative Modeling Of Granitic Melt Generation And Segregation In The Continental Crust, M. D. Jackson, Michael Cheadle, M. P. Atherton
Michael Cheadle
We present a new quantitative model of granitic (in a broad sense) melt generation and segregation within the continental crust. We assume that melt generation is caused by the intrusion of hot, mantle-derived basalt, and that segregation occurs by buoyancy-driven flow along grain edges coupled with compaction of the partially molten source rock. We solve numerically the coupled equations governing heating, melting, and melt migration in the source rock, and cooling and crystallization in the underlying heat source. Our results demonstrate that the spatial distribution and composition of the melt depends upon the relative upward transport rates of heat and …
Temperatures In Ambient Mantle And Plumes: Constraints From Basalts, Picrites, And Komatiites, C. Herzberg, P. D. Asimow, N. Arndt, Y. L. Niu, C. M. Lesher, J. G. Fitton, Michael Cheadle, A. D. Saunders
Temperatures In Ambient Mantle And Plumes: Constraints From Basalts, Picrites, And Komatiites, C. Herzberg, P. D. Asimow, N. Arndt, Y. L. Niu, C. M. Lesher, J. G. Fitton, Michael Cheadle, A. D. Saunders
Michael Cheadle
[1] Several methods have been developed to assess the thermal state of the mantle below oceanic ridges, islands, and plateaus, on the basis of the petrology and geochemistry of erupted lavas. One leads to the conclusion that mantle potential temperature (i.e., TP) of ambient mantle below oceanic ridges is 1430 degrees C, the same as Hawaii. Another has ridges with a large range in ambient mantle potential temperature (i.e., TP = 1300 - 1570 degrees C), comparable in some cases to hot spots ( Klein and Langmuir, 1987; Langmuir et al., 1992). A third has uniformly low …