Insights into magmatic processes and hydrothermal alteration of in situ superfast spreading ocean crust at ODP/IODP Site 1256 from a cluster analysis of rock magnetic properties

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doi: 10.1002/2014GC005343
Author(s): Dekkers, Mark J.; Heslop, David; Herrero-Bervera, Emilio; Acton, Gary; Krasa, David
Author Affiliation(s): Primary:
Utrecht University, Faculty of Geosciences, Utrecht, Netherlands
Other:
Australian National University, Australia
University of Hawaii at Manoa, United States
Sam Houston State University, United States
University of Edinburgh, United Kingdom
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, 15(8), p.3430-3447. Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027
Note: In English. 78 refs.; illus., incl. 2 tables
Summary: We analyze magnetic properties from Ocean Drilling Program (ODP)/Integrated ODP (IODP) Hole 1256D (6°44.1' N, 91°56.1' W) on the Cocos Plate in ∼15.2 Ma oceanic crust generated by superfast seafloor spreading, the only drill hole that has sampled all three oceanic crust layers in a tectonically undisturbed setting. Fuzzy c-means cluster analysis and nonlinear mapping are utilized to study down-hole trends in the ratio of the saturation remanent magnetization and the saturation magnetization, the coercive force, the ratio of the remanent coercive force and coercive force, the low-field magnetic susceptibility, and the Curie temperature, to evaluate the effects of magmatic and hydrothermal processes on magnetic properties. A statistically robust five cluster solution separates the data predominantly into three clusters that express increasing hydrothermal alteration of the lavas, which differ from two distinct clusters mainly representing the dikes and gabbros. Extensive alteration can obliterate magnetic property differences between lavas, dikes, and gabbros. The imprint of thermochemical alteration on the iron-titanium oxides is only partially related to the porosity of the rocks. Thus, the analysis complements interpretation based on electrofacies analysis. All clusters display rock magnetic characteristics compatible with an ability to retain a stable natural remanent magnetization suggesting that the entire sampled sequence of ocean crust can contribute to marine magnetic anomalies. Paleointensity determination is difficult because of the propensity of oxyexsolution during laboratory heating and/or the presence of intergrowths. The upper part of the extrusive sequence, the granoblastic dikes, and moderately altered gabbros may contain a comparatively uncontaminated thermoremanent magnetization. Abstract Copyright (2014), American Geophysical Union. All Rights Reserved.
Year of Publication: 2014
Research Program: IODP Integrated Ocean Drilling Program
ODP Ocean Drilling Program
Key Words: 05 Petrology, Igneous and Metamorphic; 07 Marine Geology and Oceanography; Alteration; Cluster analysis; Cocos Plate; Crust; Curie point; Dikes; East Pacific; Equatorial Pacific; Expeditions 309/312; Fuzzy logic; Gabbros; Guatemala Basin; Hydrothermal alteration; Igneous rocks; Integrated Ocean Drilling Program; Intrusions; Lava; Leg 206; Magmatism; Magnetic properties; Magnetization; Metasomatism; Natural remanent magnetization; North Pacific; Northeast Pacific; ODP Site 1256; Ocean Drilling Program; Ocean floors; Oceanic crust; Pacific Ocean; Paleomagnetism; Plate tectonics; Plutonic rocks; Remanent magnetization; Sea-floor spreading; Statistical analysis; Thermochemical remanent magnetization; Volcanic rocks
Coordinates: N064400 N064400 W0915600 W0915600
Record ID: 2016027408
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom, Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union