Expedition 335 summary

Teagle, D. A. H.; Ildefonse, Benoı̂t; Blum, Peter; Guèrin, G.; Zakharova, Natalia; Abe, Natsue; Abily, Bénédicte; Adachi, Yoshiku; Alt, Jeffrey C; Baines, Graham; Deans, J. R.; Dick, H. J.; Endo, Daisuke; Ferré, E. C.; Godard, Marguerite; Harris, Michelle; Kim, Yoon-Mi; Koepke, Juergen; Kurz, Mark D.; Lissenberg, C. Johan; Miyashita, Sumio; Morris, Antony; Ozumi, Ryo; Payot, Betchaida D.; Python, Marie; Till, J. L.; Tominaga, Masako; Wilson, Douglas S.

doi:10.2204/iodp.proc.335.101.2012

Cited by 26 publications

(4 citation statements)

References 103 publications

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“…As shown in Section 4.3, the mineral evolutionary trends with crustal height imply different modi for the magmatic accretion of the Oman paleocrust; in-situ crystallization of individual melt sills coupled with upward differentiation for the lower two thirds of the crust (Layered Gabbro Unit and LFG), and downward transport of (crystal-laden) melts originating from the AML for the upper third (UFG and DGT). Our mineral data for the lower part of our transect clearly show an upward evolutionary trend (Figure 12), which is in accord with the sheeted sill accretion model (Kelemen et al, 1997), but not with a downward transported crystal/melt suspension originated from the AML (gabbro glacier), for which straight vertical evolutionary paths with constant compositions are predicted (see Figure 17 in Teagle et al, 2012). This emphasizes the importance of further melt lenses below the AML in the deeper crust under fast-spreading ridges.…”

Section: Hybrid Formation Of the Lower Oceanic Crust In The Wadi Gideahsupporting

confidence: 78%

“…Previous IODP and Ocean Drilling Program (ODP) efforts to sample modern fast-spreading oceanic crust include Hole 504B on the southern flank of the Costa Rica Rift that penetrated 1.8 km into ∼6.9 Ma Pacific Ocean igneous basement, but recovered only lavas and dikes (Alt et al, 1996). Drill hole 1256D in the basement of the Guatemala basin formed by the EPR ∼15 Ma ago successfully cored a 1507 m long section of the upper (basaltic) oceanic crust, penetrating 76 m of the underlying gabbro sequence (Teagle et al, 2012;Wilson et al, 2006). In addition to these ODP and IODP drillings, two other prominent locations of fast-spreading oceanic crust are located at the EPR, where deeper crustal parts are exposed due to ridge tectonism: Hess Deep and Pito Deep.…”

mentioning

confidence: 99%

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A Reference Section Through Fast‐Spread Lower Oceanic Crust, Wadi Gideah, Samail Ophiolite (Sultanate of Oman): Petrography and Petrology

et al. 2022

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In the absence of a complete profile through fast‐spreading modern oceanic crust, we established a reference profile through the whole paleo crust of the Samail ophiolite (Sultanate of Oman), which is regarded as the best analogue for fast‐spreading oceanic crust on land. To establish a coherent data set, we sampled the Wadi Gideah in the Wadi‐Tayin massif from the mantle section up to the sheeted dikes and performed different analytical and structural investigations on the same suite of samples. This paper reports our studies of the lower crust, a 5 km thick pile of gabbros, focusing on petrographic features and on the results of mineral analyses. Depth profiles of mineral compositions combined with petrological modeling reveal insights into the mode of magmatic formation of fast‐spreading lower oceanic crust, implying a hybrid accretion mechanism. The lower two thirds of the crust, mainly consisting of layered gabbros, formed via the injection of melt sills and in situ crystallization. Here, upward moving fractionated melts mixed with more primitive melts through melt replenishments, resulting in a slight but distinct upward differentiation trend. The upper third of the gabbroic crust is significantly more differentiated, in accord with a model of downward differentiation of a primitive parental melt originated from the axial melt lens located at the top of the gabbroic crust. Our hybrid model for crustal accretion requires a system to cool the deep crust, which was established by hydrothermal fault zones, initially formed on‐axis at very high temperatures.

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Section: Hybrid Formation Of the Lower Oceanic Crust In The Wadi Gideahsupporting

confidence: 78%

mentioning

confidence: 99%

A Reference Section Through Fast‐Spread Lower Oceanic Crust, Wadi Gideah, Samail Ophiolite (Sultanate of Oman): Petrography and Petrology

et al. 2022

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“…The log data for the main open hole logged section are summarized in Fig. 6 along with a summary of the volcanic facies based on the core logging (Thomas and Haskins, 2013). Data from each sonde are described individually in relation to the volcanic stratigraphy in the following section.…”

Section: Wireline Logging Resultsmentioning

confidence: 99%

“…A number of aquifer feed points are known from within the upper part of the well (Thomas and Haskins, 2013) and therefore circulation of aquifer waters into the borehole may have added to this effect. An inflection to a higher temperature gradient ca.…”

Section: Dip Metermentioning

confidence: 99%

Understanding volcanic facies in the subsurface: a combined core, wireline logging and image log data set from the PTA2 and KMA1 boreholes, Big Island, Hawai`i

et al. 2019

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Abstract. To help understand volcanic facies in the subsurface, data sets that enable detailed comparisons between down-hole geophysical data and cored volcanic intervals are critical. However, in many cases, the collection of extended core intervals within volcanic sequences is rare and often incomplete due to challenging coring conditions. In this contribution we outline and provide initial results from borehole logging operations within two fully cored lava-dominated borehole sequences, PTA2 and KMA1, on the Big Island of Hawai`i. Data for spectral gamma, magnetic susceptibility, dipmeter resistivity, sonic, total magnetic field, temperature and televiewer wireline logs were successfully acquired for the open hole interval ca. 889 m to 1567 m within the PTA2 borehole. Spectral gamma was also collected from inside the casing of both wells, extending the coverage for PTA2 to the surface and covering the interval from ca. 300 to 1200 m for KMA1. High-quality core material was available for both boreholes with almost complete recovery which enabled high-resolution core-to-log integration. Gamma data are generally low commonly in the range ca. 7–20 gAPI but are shown to increase up to API of ca. 60 with some intrusions and with increases in hawaiite compositions in the upper part of PTA2. Velocity data are more variable due to alteration within porous volcanic facies than with burial depth, with a general degrease down-hole. The high-resolution televiewer data have been compared directly to the core, enabling a comprehensive analysis of the variations in the televiewer responses. This has enabled the identification of key features including individual vesicles, vesicle segregations, strained vesicles, chilled margins, rubble zones, intrusive contacts and pāhoehoe lobe morphologies, which can be confidently matched between the televiewer data and the full diameter core. The data set and results of this study include findings which should enable improved borehole facies analysis through volcanic sequences in the future, especially where down-borehole data and images but no core are available.

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