Hole U1415I

Gillis, K. M.; Snow, J.E.; Klaus, A.; Guèrin, G.; Abe, Natsue; Akizawa, Norikatsu; Ceuleneer, Georges; Cheadle, M.J.; Adrião, Á.; Faak, K.; Falloon, Trevor J.; Friedman, S.A.; Godard, M.; Harigane, Yumiko; Horst, A. J.; Hoshide, Takashi; Ildefonse, Benoı̂t; Jean, M. M.; John, B. E.; Koepke, J.H.; Machi, S.; Maeda, J.; Marks, Naomi; McCaig, A.M.; Meyer, R.; Morris, A.; Nozaka, Toshio; Python, Marie; Saha, Abhishek; Wintsch, Robert P.

doi:10.2204/iodp.proc.345.109.2014

Cited by 4 publications

(10 citation statements)

References 34 publications

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“…Large oikocrysts may form in a clinopyroxene-poor groundmass by a crystal coarsening process (Mills et al, 2011), where abundant small nuclei are dissolved and recrystallized as fewer large oikocrysts over relic crystals. In the Hess Deep sample, the random orientation of plagioclase chadacrysts in the clinopyroxene core1 HD and the preferred orientation of clinopyroxene rim HD plagioclase chadacrysts parallel to the main foliation (Figures 1B, 2D; see also Gillis et al, 2014b) suggests crystallization of clinopyroxene core1 HD predates cumulate compaction, while clinopyroxene rim HD postdates compaction. Leuthold et al (2014a) interpreted similar textures in the Rum layered intrusion as the consequence of effective compactionrelated grain alignment because of the porosity increase following melt percolation and partial melting.…”

Section: Melt Hybridization At the Origin Of The Clinopyroxene Core2mentioning

confidence: 92%

“…Fine-grained Cr-spinel grains occur along clinopyroxene core1 HD -core2 HD and core2 HD -rim HD contacts, in close spatial association with plagioclase. The well-defined foliation in the groundmass appears to wrap around clinopyroxene oikocrysts (see Gillis et al, 2014b). The groundmass is composed of fine-grained (ca.…”

Section: East Pacific Rise Poikilitic Gabbromentioning

confidence: 99%

“…From left to right, layers of gabbro grading to a medium-grained poikilitic gabbro with interstitial clinopyroxene, to a fine-grained troctolite, in contact with a coarse-grained poikilitic gabbro. Gillis et al, 2014b). Clinopyroxene oikocrysts in a foliated troctolitic groundmass.…”

Section: Supplementary Materialsmentioning

confidence: 99%

“…See alsoFigure A.1 and Presentation 1. (B) Hess Deep (2 • 15 ′ N, 101 • 33 ′ W, East Pacific Rise) U1415I_4R_2_9-13 lower oceanic crust sample (seeGillis et al, 2014b) with clinopyroxene oikocrysts in a foliated troctolitic groundmass. See alsoFigure A.2.…”

mentioning

confidence: 99%

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Partial Melting of Lower Oceanic Crust Gabbro: Constraints From Poikilitic Clinopyroxene Primocrysts

et al. 2018

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Cross-section of slow-spreading ridges, showing the different occurrences of melt in the oceanic crust (based on Sinton and Detrick, 1992; Dick et al., 2008). Gabbro s.l. includes troctolite, olivine-gabbro, gabbro, gabbronorite and ferrogabbro. Also dunite occurs along the Moho. Young hot crustal gabbro reacts (i.e., partial melting, hybridization, recrystallization) with invading primitive mantle-derived melt. Crystals, rocks and melt chemistry and texture are modified.

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Section: Melt Hybridization At the Origin Of The Clinopyroxene Core2mentioning

confidence: 92%

Section: East Pacific Rise Poikilitic Gabbromentioning

confidence: 99%

Section: Supplementary Materialsmentioning

confidence: 99%

mentioning

confidence: 99%

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Partial Melting of Lower Oceanic Crust Gabbro: Constraints From Poikilitic Clinopyroxene Primocrysts

et al. 2018

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“…While conducting test measurements with a smaller measurement interval of 1 mm in order to look for variations of a* and b* with the olivine contents in the layered gabbronorites recovered from Section 345-U1415I-4R-1, we identified a problem with the instrument; it was recording different values of these parameters over successive series of measurements on the same core pieces (see details in the "Hole U1415I" chapter [Gillis et al, 2014b]). A series of tests with color standards was then conducted.…”

Section: Reflectance Spectrophotometry and Colorimetrymentioning

confidence: 99%

Methods

Gillis¹,

Snow²,

Klaus³

et al. 2014

Proceedings of the IODP

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Fluid Infiltration Through Oceanic Lower Crust in Response to Reaction‐Induced Fracturing: Insights From Serpentinized Troctolite and Numerical Models

et al. 2020

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The mechanisms of fluid penetration through the gabbroic lower crust are important for the hydration of oceanic lithosphere. In the Oman ophiolite, which preserves an entire sequence of oceanic lithosphere formed at a fast-spreading ridge, the layered gabbros and dunites are extensively serpentinized. In this paper, we describe the characteristic textures of serpentinized troctolite and olivine gabbros recovered from the CM1A site of the Oman Drilling Project. In the troctolite, an olivine mesh texture is pervasively developed and is characterized by two types of veins: early lizardite + brucite + magnetite and late Al-rich lizardite + magnetite. These veins suggest the initiation of serpentinization at <350°C and a supply of Si and Al from plagioclase during the later stages of serpentinization. Plagioclase surrounding serpentinized olivine grains commonly shows radial fracturing. Numerical simulations using the discrete element method applied to coupled fluid flow, reaction, and fracturing reveal that volume expansion of olivine grains during serpentinization results in the simultaneous fracturing of olivine and surrounding plagioclase, and that the thermal stress during cooling of oceanic lithosphere might also cause preferential olivine fracturing prior to serpentinization. The simulations also predict a self-organizing fracture network that connects the olivine grains and passes through both olivine-rich and olivine-poor layers, resulting in permeability enhancement during serpentinization. Our results suggest that reaction-induced fracturing plays an essential role in the infiltration of seawater through the lower crust and into the mantle within oceanic lithosphere. Plain Language Summary The Oman ophiolite preserves evidence of pervasive serpentinization of the lower crust, Moho transition zone, and uppermost mantle. In this study, we investigated a troctolite and olivine gabbros from the CM1A site of the Oman Drilling Project, and compared fracture patterns in these rocks with those predicted by discrete element method (DEM) numerical simulations. In the troctolite, olivine grains are serpentinized to form a mesh texture, and radial fractures are developed in plagioclase and clinopyroxene adjacent to olivine. The olivine mesh texture consists of two types of veins: early serpentine + brucite + magnetite and late Al-rich serpentine + magnetite. Numerical simulations of coupled fracturing, reaction, and fluid flow reproduced the observed fracture patterns and indicate that reaction-induced fracturing plays a key role in permeability enhancement within the lower oceanic crust during low-temperature alteration.

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Hole U1415I

Cited by 4 publications

References 34 publications

Partial Melting of Lower Oceanic Crust Gabbro: Constraints From Poikilitic Clinopyroxene Primocrysts

Partial Melting of Lower Oceanic Crust Gabbro: Constraints From Poikilitic Clinopyroxene Primocrysts

Methods

Fluid Infiltration Through Oceanic Lower Crust in Response to Reaction‐Induced Fracturing: Insights From Serpentinized Troctolite and Numerical Models

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