Paleomagnetism of the Xigaze ophiolite and flysch (Yarlung Zangbo suture zone, southern Tibet): latitude and direction of spreading

Depression-fill within a forearc setting, Aptian-Turonian, Xigaze, Tibet

“…Reconstruction of the evolution of the forearc basin is based partly on palaeomagnetic evidence (Pozzi et al 1984) and partly on outcrop data. Development of a residual basin commenced with subduction along the line of a major transform.…”

The Himalayan Orogenic Segment

“…They expose more than 3500 km of the fresh, uniform Jungbwa peridotite up to 500 m thick and made up mainly of harzburgite (Gansser, 1964); -in southern Tibet, ophiolites may be followed in the Xigaze area for some 200 km east to west. Only recently surveyed (Chang et al 1977;Bally et al 1980;Nicolas et al 1981), they have bee-n----studied in some detail, and three relatively preserved massifs of this band (Angren, Xigaze s.s. and Dagzhuka) have been mapped at a 1:25,000 scale (Girardeau et al 1984(Girardeau et al , 1985a. These scattered klippen are quite similar and display somewhat peculiar characteristics.…”

“…The direction varies from N60 -80 0 E for Xigaze (Girardeau et al 1985b) to N1400E for Spongtang (Reuber, 1986). However, for Xigaze, this does take into account the 85 ± 20° of counterclockwise rotation deduced from palaeomagnetic studies by Pozzi et al (1984) that would bring the ridge to an orientation of N175°E ± 25~ughly perpendicular to what would be normally guessed. In this respect, it is interesting to note that the oldest magnetic anomalies off the west coast of Australia, the so-called MO to M 10 anomalies, ranging from 108 to 122 Ma, have a somewhat similar dLrection with regard to peninsular India (Larson et al 1979;Johnson et al 1980).…”

“…In fact, the age of the Xigaze ophiolite deduced either from the radiolarites interbedded in the pillow lavas (110 Ma: Marcoux in Girardeau et al 1984) or directly from the U-Pb analysis of the magmatite (120 ± 10 Ma: Gopel et al 1984) corresponds to the M series of anomalies. According to the palaeomagnetic study of Pozzi et al (1984) the Xigaze ophiolite was then lying between 10 and 20 0 N, close to the southern margin of the Lhasa block.…”

Geophysical expression of the Leka Ophiolite, Norway, modeled from integrated gravity, magnetic and petrophysical data

“…Spicer et al (2010) using highresolution aeromagnetic maps developed a 3D model of the Betts Cove ophiolite complex in Newfoundland as a syncline with normal and high-angle reverse faults. Paleomagnetism was used to detect the age of a low-temperature alteration event during the midCarboniferous, that was previously unknown in the Shetland Ophiolite (Taylor, 1988), and Pozzi et al (1984) used paleomagnetism to define the paleo-orientation and paleo-latitude of the spreading center that had created the Xigaze ophiolite in Tibet.…”