#Obduction hints filetype pdf series
It is evidenced by a series of marine sedimentary rocks, and can be regarded as a miniature of rifting within Zealandia, and even the partition of Zealandia from Gondwana. įrom the Upper Cretaceous to Eocene, proto-New Caledonia transformed into an extensional tectonic setting. Rocks in Koh-Central, Teremba and Boghen Terranes on the island suggest the units were emplaced and compressed between a volcanic arc and the associated subduction zone (known as a forearc basin along a collisional plate boundary). In the Permian, the Island was initially located in the southeastern margin of the huge supercontinent of Pangea, and then in the united southern continent of Gondwana. Volcanism beneath the ocean, then transported and scrapped off during collision between tectonic plates Terrestrial towards marine, and back to lacustrine sedimentation Volcanism in the ocean, then obducted onto the island during collision between tectonic plates Mafic to ultramafic intrusive and extrusive igneous Intrusive volcanism to form plutons and dykes Overview of the regional geologyīrief summary of the rock units on Grande Terre Thrusting, exhumation and folding of some of the units have contributed to the rugged topography of the main island, with Mont Panié and Mount Humboldt being the highest points (over 1,600 m). As shown on the map, the landmass is elongated in a NW-SE orientation, which is similar to the distribution patterns of most of the geological units. After New Zealand, it is the second-largest subaerial landmass, and the northernmost part of this continent. Ĭurrently, New Caledonia is located on the Indo-Australian Plate and the largely submerged continent of Zealandia. Mining of valuable metals from this unit has been an economical pillar of New Caledonia for more than a century. The unit consists of ore-rich ultramafic rocks thrust onto the main island. The mantle-derived Eocene Peridotite Nappe is the most significant and widespread unit (labelled as "Ophiolites" and coloured in bright green in Fig. Their formation is driven by alternate plate collisions and rifting. The geology of New Caledonia includes all major rock types ( igneous, sedimentary, and metamorphic), which here range in age from ~290 million years old (Ma) to recent. Fig.1 A simplified geological map of New Caledonia with a cross-section, modified by Xu and Liu (2019)