New Caledonia Obducted Peridotite Nappe: Offshore Extent and Implications for Obduction and Postobduction Processes

Abstract

One of the largest ophiolitic peridotite masses in the world covers a quarter of the island of Grande Terre, New Caledonia. The Peridotite Nappe was obducted during the Eocene, is weakly deformed, and corresponds to the highest of a structurally simple pile of thrust nappes. We present new marine seismic data that allow us to track the offshore continuation of the Peridotite Nappe along strike for a distance of more than 500 km south of New Caledonia and to image its preobduction, synobduction, and postobduction sedimentary records. Offshore, the Peridotite Nappe underlies a ~150 km wide and 2 km deep basin. Flat‐topped horsts of peridotite are clearly bounded by major normal faults; in contrast, faults are obscure onland. To the east, the Peridotite Nappe roots along the eastern margin of the Félicité Ridge (new name), a ~300 × 25 km dome‐shaped ridge, which we interpret as being the southern extension of the high‐pressure/low‐temperature metamorphic core complex observed in New Caledonia. Two alternative tectonic models address the relative timing and relationships between Peridotite Nappe emplacement, uplift of a metamorphic core complex, and extensional tectonics. These models provide new ideas for the understanding the formation of the eastern margin of the Zealandia continent. Our results contribute to an understanding of how oceanic mantle is emplaced onto continental margins.

Structure of the Offshore Obducted Oman Margin: Emplacement of Semail Ophiolite and Role of Tectonic Inheritance

“…This study exemplifies the influence of tectonic inheritance and pre-obduction margin architecture on obduction processes, in particular by controlling the amount of subducted continental and/or oceanic material, the later tectonic activity, as well as the location and size of the sedimentary basins. While a detailed comparison with other obduction settings worldwide is beyond the scope of the present study, striking similarities exist with examples that have escaped collision, that is, New Caledonia (Brovarone et al, 1996;Cluzel, 2001;Patriat et al, 2018) and Timor (Linthout et al, 1994(Linthout et al, , 1997. Both the offshore architecture and late-obduction extension in New Caledonia compare well with northern Oman (Lagabrielle et al, 2013;Patriat et al, 2018).…”

“…While a detailed comparison with other obduction settings worldwide is beyond the scope of the present study, striking similarities exist with examples that have escaped collision, that is, New Caledonia (Brovarone et al, 1996;Cluzel, 2001;Patriat et al, 2018) and Timor (Linthout et al, 1994(Linthout et al, , 1997. Both the offshore architecture and late-obduction extension in New Caledonia compare well with northern Oman (Lagabrielle et al, 2013;Patriat et al, 2018). A sharp lateral contrast in continental structure, distribution of HP-LT rocks and even geochemistry of the ophiolite is also observed in New Caledonia, north and south of the island (Brovarone et al, 1996;Cluzel, 2001;Patriat et al, 2018).…”

“…Both the offshore architecture and late‐obduction extension in New Caledonia compare well with northern Oman (Lagabrielle et al., 2013; Patriat et al., 2018). A sharp lateral contrast in continental structure, distribution of HP‐LT rocks and even geochemistry of the ophiolite is also observed in New Caledonia, north and south of the island (Brovarone et al., 1996; Cluzel, 2001; Patriat et al., 2018). Noteworthily, the short time delay (<5 Ma) between maximum continental subduction of the margin and the onset of distributed extension, on both the continent and the ophiolite above, is comparable for all three settings (Oman: ∼80 to 75 Ma; New Caledonia: 40 to 35 Ma; Timor: 8 to 4 Ma).…”

Subduction-Induced Fractionated Highly Siderophile Element Patterns in Forearc Mantle

“…The New Caledonia ophiolites are exposed in a large massif (the Massif du Sud) occurring in the south of the main island and smaller isolated massifs along the west coast, such as Me Maoya, Kopeto, Koniambo, and Tiebaghi ( Figure 1a). They are connected with the oceanic lithosphere of the Loyalty Basin [20,21] and have been regarded as the archetype of forearc ophiolites [22]. The New Caledonia ophiolites are allochthonous and were thrust from NNE to SSW over the continental basement of the main island.…”

Extrusion of subducted crust explains the emplacement of far-travelled ophiolites

“…For detailed explanation and references regarding the datasets (c-e) see Supplementary Note 1 and Supplementary Tables 1 and 2. Simplified cross sections showing the structure of the Oman 13 (a) and New Caledonia 56,57 (b) ophiolites and their structural relationship to the underlying continental rocks. The far-travelled ophiolite sheets are separated from their oceanic root by exhumed continental units, which show a transition from non-metamorphic to high metamorphic grade.…”