Title: Ultramafic and mafic dredge samples from the equatorial Mid-Atlantic ridge and fracture zones
Abstract: Journal of Geophysical Research (1896-1977)Volume 81, Issue 23 p. 4087-4103 Vertical Structure of the Oceanic Lithosphere Ultramafic and mafic dredge samples from the equatorial Mid-Atlantic ridge and fracture zones M. Prinz, M. PrinzSearch for more papers by this authorK. Keil, K. KeilSearch for more papers by this authorJ. A. Green, J. A. GreenSearch for more papers by this authorA. M. Reid, A. M. ReidSearch for more papers by this authorE. Bonatti, E. BonattiSearch for more papers by this authorJ. Honnorez, J. HonnorezSearch for more papers by this author M. Prinz, M. PrinzSearch for more papers by this authorK. Keil, K. KeilSearch for more papers by this authorJ. A. Green, J. A. GreenSearch for more papers by this authorA. M. Reid, A. M. ReidSearch for more papers by this authorE. Bonatti, E. BonattiSearch for more papers by this authorJ. Honnorez, J. HonnorezSearch for more papers by this author First published: 10 August 1976 https://doi.org/10.1029/JB081i023p04087Citations: 76AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Abstract Dredge samples selected for study from the Vema Romanche, and Chain fracture zones include serpentinized spinel lherzolites, ilmenite norites, oceanic tholeiites, and a teschenite. The serpentinized ultramafic rocks from the fracture zones are chemically and mineralogically similar to spinel lherzolites (or harzburgites) found as ultramafic tectonites or cumulates. The primary mineral assemblage is olivine (Fo89.3–91.6) orthopyroxene (En87.0–88.8) clinopyroxene (Wo38.4–49.0 En46.4–55.5 Fs4.0–6.1), and a spinel rich in Cr and Al. These rocks apparently represent depleted upper mantle exposed at the base of the fracture zones or diapirically intruded along the fracture zones, or, alternatively, ultramafic cumulates such as in ophiolite complexes. The TiO2-rich norites (TiO2 4.00–5.88 wt %) are iron-rich (FeO + 0.9 Fe2O3 17.3–18.2 wt %) and compositionally resemble the late-stage Skaergaard rocks. Major minerals are plagioclase (An37–68), orthopyroxene (En58–70), clinopyroxene (Wo40–44 En15–17Fs41–43), low-Mg ilmenite, and low-Ti magnetite. Low K2O oceanic tholeiites from the central rift valley on the ridge are typical midocean ridge basalts. Megacrysts of plagioclase that include olivine grains are believed to be of cognate origin. The teschenite, which closely resembles the Black Jack sill teschenite, contains high-Ca titaniferous augite (Wo46–48En23–31Fs15–31), plagioclase (An10–75), ilmenite, titaniferous magnetite, analcite, and zeolites. The diversity of rock types and the occurrence of alkalic basalt imply complex plutonic processes occurring within the fracture zones. Citing Literature Volume81, Issue23Solid Earth and Planets10 August 1976Pages 4087-4103 RelatedInformation
Publication Year: 1976
Publication Date: 1976-08-10
Language: en
Type: article
Indexed In: ['crossref']
Access and Citation
Cited By Count: 109
AI Researcher Chatbot
Get quick answers to your questions about the article from our AI researcher chatbot