Crustal Extension between the Tonga and Lau Ridges: Petrologic and Geophysical Evidence

Abstract

Research Article| February 01, 1972 Crustal Extension between the Tonga and Lau Ridges: Petrologic and Geophysical Evidence JOHN G SCLATER; JOHN G SCLATER Marine Physical Laboratory, Scripps Institution of Oceanography, University of California, La Jolla, California 92037 Search for other works by this author on: GSW Google Scholar JAMES W HAWKINS; JAMES W HAWKINS Geological Research Division, Scripps Institution of Oceanography, University of California, La Jolla, California 92037 Search for other works by this author on: GSW Google Scholar JACQUELINE MAMMERICKX; JACQUELINE MAMMERICKX Geological Research Division, Scripps Institution of Oceanography, University of California, La Jolla, California 92037 Search for other works by this author on: GSW Google Scholar CLEMENT G CHASE CLEMENT G CHASE Department of Scripps Institution of Oceanography, University of California, La Jolla, California 92037 PRESENT ADDRESS (CHASE): DEPARTMENT OF GEOLOGY AND GEOPHYSICS, UNIVERSITY OF MINNESOTA, MINNEAPOLIS, MINNESOTA 55455 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1972) 83 (2): 505–518. https://doi.org/10.1130/0016-7606(1972)83[505:CEBTTA]2.0.CO;2 Article history received: 26 Apr 1971 rev-recd: 30 Jul 1971 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation JOHN G SCLATER, JAMES W HAWKINS, JACQUELINE MAMMERICKX, CLEMENT G CHASE; Crustal Extension between the Tonga and Lau Ridges: Petrologic and Geophysical Evidence. GSA Bulletin 1972;; 83 (2): 505–518. doi: https://doi.org/10.1130/0016-7606(1972)83[505:CEBTTA]2.0.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 Lau Basin, which lies between the Tonga and Lau Ridges, is characterized by an absence of sediment, high but variable heat flow, and a confused magnetic anomaly pattern. A ridge 300 km long and 40 km wide runs northwest-southeast through the western part of the basin. This ridge is composed of fresh tholeiitic basalt and is associated with a linear band of shallow-focus earthquakes ( < 70 km). Chemical analysis of unaltered glassy and aphanitic phenocryst-free pillow fragments indicates that the parent liquids may have been derived from mantle depths of about 50 km.The geophysical and geological data are interpreted within the framework of the theory of plate tectonics. It is suggested that the ridge and related earthquake epicenters mark the boundary between the India plate and a much smaller plate, the Tonga plate, which lies between the India plate and the Tonga Trench. The boundary is a transform fault marking the direction of motion of the two plates. A revised crustal consumption rate of 11 cm/yr for the Tonga Trench is required if the Tonga-India plate separation is added to the India-Pacific plate convergence. Continued NW-SE dilation and basalt intrusion during the past 10 m.y. has separated the Tonga and Lau Ridges and can explain the fresh basalt, the absence of sediment, and the high heat flow in the Lau Basin. This basin, although lying below the ridges on either side, has an average elevation more than 3,000 m above that of the deep Pacific. Intrusion of hot material at the center of the basin can account for this increase in elevation. The classic concept of the "andesite line," separating oceanic and continental crust, clearly has no meaning as an indication of crustal type, as oceanic crust can be generated behind island arcs. 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.