| Abstrakt: |
With 3 figures and 4 tables Abstract:?The formation of the Central European and Tarim Large Igneous Provinces (LIPs) in the Early Permian coincided with the demise of the Variscan and the Southern Tianshan orogens, respectively. The Early Triassic Siberian LIP was formed in the wake of the Western Altaid orogeny in the Late Permian. These processes coincided with the development of the majority of known Late Palaeozoic and Early Mesozoic hydrothermal and magmatic ore deposits in the corresponding orogenic domains. Nickel-copper(-PGE) deposits followed directly from the evolution of the (ultra-)mafic melts which make up the LIPs. In Western Siberia, the diverse assemblage of associated noble and base metals in the Noril’sk-Talnakh Ni-Cu(-PGE) deposits suggests these metals also had their source in the mantle domain from which the (ultra-)mafic melts were generated. The same metals variably found their way into the hydrothermal ore deposits in the defunct Variscan and Southern Tianshan orogenic domains. These ore deposits have traditionally been viewed as a result of orogenic processes. However, their ages, together with the timing and nature of their by then intracontinental tectonic control cause uncertainty concerning the role of the orogens. In view of their mantle sources in their association with the Siberian LIP, the mantle contribution to these Late Palaeozoic hydrothermal ore deposits in the orogenic belts may have been more significant than previously thought. An orogenic contribution to melting of mantle complexes and to mineralisation may have resided in the earlier modification of subcontinental mantle domains by subduction of oceanic lithosphere. In all three cases, the controlling tectonic setting of orogenic cessation, LIP formation and mineralisation was dominated by translithospheric strike-slip deformation, possibly in combination with orogenic collapse and lithosphere delamination. In view of their recurrence, the orogen-lip sequences were probably not fortuitous. The controlling strike-slip faults were principal elements of the lithosphere-scale dynamic framework that led to the amalgamation of Pangaea. At this scale, the exceptionally large volume of the Siberian LIP may, in addition to the strike-slip dissection of the lithosphere, have been related to extension in the continental lithosphere of the margin of the Supercontinent (cf. Gutiérrez-Alonso et al. 2008). The peripheral extension was associated with compression in its centre. The explanation of these Large Igneous Provinces does not require the concept of an active mantle plume because deep-reaching strike-slip deformation, orogenic collapse and lithosphere delamination involved in the destruction of the orogenic edifices can have caused decompression melting in large domains of the subcontinental mantle.? |
