de.pangaea.dataset871023 und dataset PANGAEA

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https://www.pangaea.de/ information pointOfContact 2026-06-18T12:51:15Z https://doi.pangaea.de/10.1594/PANGAEA.871023 1979-01-01 publication https://doi.org/10.1594/PANGAEA.871023 Malcolm, Frieda L author PANGAEA

info@pangaea.de

https://www.pangaea.de/ information publisher tableDigital Supplement to: Malcolm, Frieda L (1979): Petrography, mineral chemistry and microstructures of gabbros from the Mid-Cayman Rise Spreading Center [thesis]. Master thesis, University of Albany, 121 pp, https://scholarsarchive.library.albany.edu/cas_daes_geology_etd/56/ The suite of gabbroic rocks collected by the DSRV ALVIN in 1976 and 1977 from the walls of the Mid-Cayman Rise spreading center were studied in detail to provide the best available data on plutonic rocks sampled directly from the ocean floor. The rock types studied include variably deformed and altered gabbros, orthopyroxene gabbros, olivine gabbros and troctolites, and a few amphibolites. Mineral chemical analyses suggest that the various rock types are representative of a fractionation trend from magnesian troctolites through olivine and clinopyroxene gabbros to iron-enriched orthopyroxene gabbros. Within many individual samples, the primary mineral phases are apparently chemically homogeneous despite sometimes considerable alteration, which suggests reequilibration after original crystallization. Variation in mineral-chemistry across the suite is larger than previously reported for ocean-floor gabbros; this may be due to the larger population of this study. The primary or secondary nature of plagioclase and amphibole must be distinguished in discussions of the igneous processes involved in the genesis of these rocks. In this suite, textural evidence is often inconclusive, and although sodic chemistry is assumed to indicate a secondary origin for plagioclase, no chemical indicator was found to apply to amphiboles. Many different deformation textures are observed in the samples, indicating considerable variation in the conditions of deformation within this slowly accreting ridge environment. Ductile features range from mechanical twins and bent crystals (low strain) to complete recrystallization with a well-developed foliation (high strain). Textures suggestive of cataclasis include zones .1-10 mm wide containing very fine, irregular grains; kinked and cracked grains, usually very undulose; and crosscutting fractures. These textures may occur separately, or next to or overprinting each other. Of the variables controlling the formation of deformation features, temperature and water pressure are most easily estimated. Minimum temperature during deformation is suggested by minimum temperature of formation of mineral assemblages unaffected by this deformation. This temperature is greater than 550°C (epidote-amphibolite facies) for the majority of features observed, although sampling may have introduced a bias away from lower temperature features. Observations suggest enhanced recrystallization where the primary mineralogy has been hydrated to a greater extent. Theoretically, confining pressure for the gabbroic rocks in this suite may have varied from about .3-.9kb; fluid pressure should have been within these limits. Based on mineralogical evidence, cataclastic and ductile textures developed at both high and moderate temperatures. This suggests that strain rates and/or pressure vary considerably within regions where rocks are hot as well as where rocks are cooler, and that after high-temperature deformation some rocks cooled quickly enough to prevent significant recrystallization while others cooled more slowly. These interpretations indicate that the Cayman plutonics were raised to their present position by motions which varied from place to place and time to time, and suggests that the structural history of plutonic.rocks formed at slowly accreting plate boundaries is highly variable and complex. completed Malcolm, Frieda L principalInvestigator NOAA-MMS NOAA and MMS Marine Minerals Geochemical Database theme 1995-01-01 creation PANGAEA

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https://www.pangaea.de/ information pointOfContact copyright copyright CC-BY-3.0: Creative Commons Attribution 3.0 Unported textTable und geoscientificInformation -81.613 -81.55000000000001 17.632 17.983 1977-04-07T00:00:00 1977-04-13T00:00:00 0.0 0.0 From 1983 until 1989 NOAA-NCEI compiled the NOAA-MMS Marine Minerals Geochemical Database from journal articles, technical reports and unpublished sources from other institutions. At the time it was the most extended data compilation on ferromanganese deposits world wide. Initially published in a proprietary format incompatible with present day standards it was jointly decided by AWI and NOAA to transcribe this legacy data into PANGAEA. This transfer is augmented by a careful checking of the original sources when available and the encoding of ancillary information (sample description, method of analysis...) not present in the NOAA-MMS database. Event label thematicClassification Identification thematicClassification DEPTH, sediment/rock physicalMeasurement m m Position thematicClassification Visual description Deposit type thematicClassification Quantity of deposit thematicClassification Substrate type thematicClassification Sediment type thematicClassification Description thematicClassification text/tab-separated-values unknown https://doi.pangaea.de/10.1594/PANGAEA.871023?format=textfile download dataset The data set was checked for completeness, correctness, and consistency of metainformation. Validity of used methods was checked and - if applicable - precision and range of data. EVENT LABEL: ALV-737 (AL73700) * LATITUDE: 17.983000 * LONGITUDE: -81.613000 * DATE/TIME: 1977-04-07T00:00:00 * ELEVATION: -3655.0 m * CAMPAIGN: ALV737 * BASIS: Alvin * METHOD/DEVICE: Grab 1977-04-07T00:00:00 EVENT LABEL: ALV-738 (AL73800) * LATITUDE: 17.983000 * LONGITUDE: -81.550000 * DATE/TIME: 1977-04-08T00:00:00 * ELEVATION: -3452.0 m * CAMPAIGN: ALV738 * BASIS: Alvin * METHOD/DEVICE: Grab 1977-04-08T00:00:00 EVENT LABEL: ALV-739 (AL73900) * LATITUDE: 17.632000 * LONGITUDE: -81.607000 * DATE/TIME: 1977-04-10T00:00:00 * ELEVATION: -3676.0 m * CAMPAIGN: ALV739 * BASIS: Alvin * METHOD/DEVICE: Grab 1977-04-10T00:00:00 EVENT LABEL: ALV-740 (AL74000) * LATITUDE: 17.952000 * LONGITUDE: -81.580000 * DATE/TIME: 1977-04-11T00:00:00 * ELEVATION: -3114.0 m * CAMPAIGN: ALV740 * BASIS: Alvin * METHOD/DEVICE: Grab 1977-04-11T00:00:00 EVENT LABEL: ALV-741 (AL74100) * LATITUDE: 17.952000 * LONGITUDE: -81.583000 * DATE/TIME: 1977-04-12T00:00:00 * ELEVATION: -3356.0 m * CAMPAIGN: ALV741 * BASIS: Alvin * METHOD/DEVICE: Grab 1977-04-12T00:00:00 EVENT LABEL: ALV-742 (AL74200) * LATITUDE: 17.973000 * LONGITUDE: -81.560000 * DATE/TIME: 1977-04-13T00:00:00 * ELEVATION: -2775.0 m * CAMPAIGN: ALV742 * BASIS: Alvin * METHOD/DEVICE: Grab 1977-04-13T00:00:00 Source 1992-01-01 publication https://doi.org/10.7289/V52Z13FT Grant, John Bruce author Moore, Carla J

carla.j.moore@noaa.gov

https://orcid.org/0000-0002-2610-8648 information author Alameddin, George author Chen, Kuiying author Barton, Mark author documentDigital National Geophysical Data Center, NOAA Further details 1992-01-01 publication https://doi.org/10.7289/V53X84KN Warnken, Robin R

rrw@luna.ngdc.noaa.gov

author Virden, William T author Moore, Carla J

carla.j.moore@noaa.gov

https://orcid.org/0000-0002-2610-8648 information author documentDigital National Geophysical Data Center, NOAA