|Magnetic and Structural Studies of the Lower Crustal Exposure of Ocean Lithosphere: Kane Megamullion, Mid-Atlantic Ridge 23°30'N|
Maurice Tivey, Brian Tucholke, Henry Dick
The cruise focuses on the Kane megamullion or oceanic core-complex located at 23º 30’N, 45º 20’W on the western flank of the Mid-Atlantic Ridge at Kane (MARK) area. The Kane megamullion is interpreted to be the exhumed footwall of a long-lived (~1.2 m.y.) normal "detachment" fault near Kane Fracture Zone (F.Z.) on 2.7 million year-old crust. This exhumation appears to have exposed an upper-mantle section of lithosphere and a deep-crustal section that is readily accessible to survey, sampling, and eventual drilling. The fault surface is characterized by smooth topography interrupted by a distinct series of linear ridges, corrugations, or mullions that are oriented parallel to the spreading flow-line direction and perpendicular to the spreading axis and abyssal hill lineations. The Kane megamullion area also shows well defined magnetic lineations of Chron 2A without any major disruptions, implying the presence of coherently magnetized source rocks. The three primary scientific questions addressed with this program are:
• How are magnetization and the polarity-reversal history of Earth's magnetic field recorded at mid-crustal and deeper levels?
• What conditions of magmatism at the rift axis attend formation of megamullions, and what are the resulting composition and intrusive relations at mid-crustal and deeper levels?
• What are the nature of strain accommodation and evolution of strain localization in the shear zone of a major normal fault in ocean crust?