Relic magma chamber structures preserved within the Mesozoic North Atlantic crust?

Research Article| September 01, 1988 Relic magma chamber structures preserved within the Mesozoic North Atlantic crust? JILL McCARTHY; JILL McCARTHY 1U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 940252Geophysics Department. Stanford University, Stanford, California 94305 Search for other works by this author on: GSW Google Scholar JOHN C. MUTTER; JOHN C. MUTTER 3Lamont-Doherty Geological Observatory, Palisades, New York 10964 Search for other works by this author on: GSW Google Scholar JANET L. MORTON; JANET L. MORTON 1U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar NORMAN H. SLEEP; NORMAN H. SLEEP 2Geophysics Department. Stanford University, Stanford, California 94305 Search for other works by this author on: GSW Google Scholar GEORGE A. THOMPSON GEORGE A. THOMPSON 2Geophysics Department. Stanford University, Stanford, California 94305 Search for other works by this author on: GSW Google Scholar Author and Article Information JILL McCARTHY 1U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 940252Geophysics Department. Stanford University, Stanford, California 94305 JOHN C. MUTTER 3Lamont-Doherty Geological Observatory, Palisades, New York 10964 JANET L. MORTON 1U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 NORMAN H. SLEEP 2Geophysics Department. Stanford University, Stanford, California 94305 GEORGE A. THOMPSON 2Geophysics Department. Stanford University, Stanford, California 94305 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1988) 100 (9): 1423–1436. https://doi.org/10.1130/0016-7606(1988)100<1423:RMCSPW>2.3.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation JILL McCARTHY, JOHN C. MUTTER, JANET L. MORTON, NORMAN H. SLEEP, GEORGE A. THOMPSON; Relic magma chamber structures preserved within the Mesozoic North Atlantic crust?. GSA Bulletin 1988;; 100 (9): 1423–1436. doi: https://doi.org/10.1130/0016-7606(1988)100<1423:RMCSPW>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The North Atlantic Transect seismic reflection data, collected southwest of Bermuda, have been reinterpreted following post-stack migration and reveal two major intracrustal reflections. The shallower of these two events, located ∼1 s below the igneous basement, is a subhorizontal, undulating surface that in some places is continuous for as much as 10 km. On the basis of its position within the section and its laterally discontinuous nature, we believe that this upper crustal reflection corresponds to the intermittently sharp contact between the sheeted dikes and the underlying isotropic gabbro. A second set of lower crustal reflections, dipping ∼20°-40° eastward, is also prominent on the migrated profile and terminates downdip against the subhorizontal reflection Moho. Several lines of evidence argue against these features being either artifacts or out-of-the-plane events. Instead, their presence may be ascribed either to crustal-penetrating fault zones or to mafic-ultramafic cumulate layers frozen into the oceanic crust at the time of formation at the paleo-spreading center. Because of the laminated character of these events and their typical occurrence within 1.0 to 1.5 s of the reflection Moho, we prefer a compositional versus a structural interpretation for their origin.The gradual thinning in the crust approaching the fracture zones is shown to be more complex than was originally inferred; although the interpretation that the crust gradually thins toward fracture zones may still apply in a few localities, significant departures are recognized elsewhere. Similarly, the improved image on the migrated profile documents an increase in complexity across the localized region directly surrounding the Blake Spur fracture zone. An interpretation advocating crustal thickening in this narrow zone is proposed as an alternative to the crustal-thinning model of Mutter and others. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.