The cold and hot collisional orogens: Thermal regimes and metallogeny of the Alpine versus Himalayan-Tibetan belts

It is commonly believed that the thermal regime of collisional orogens evolves from cold to hot with time. Here, we compare the Alpine and Himalayan-Tibetan orogens in terms of their thermal regimes recorded in metamorphic rocks, volcanic suites and related xenoliths, and main mineralization types. The results highlight the fact that the Alpine orogen mostly remained in a relatively cold regime from oceanic subduction to post collision stages. In contrast, most of the Himalayan-Tibetan Plateau rapidly reached and was maintained in a relatively hot regime during the whole course of the collision, except for narrow plate boundary domains. We therefore propose that the thermal regime of collision is inherent to a given geodynamic setting, and that the Alpine and Himalayan-Tibetan orogens represent two fundamental types of collisional orogens, cold and hot, respectively. The main mineral deposit types within collisional orogen include Mississippi Valley type Pb-Zn, orogenic gold, and porphyry Cu deposits. The Mississippi Valley type Pb-Zn and orogenic gold deposits can occur in both cold and hot orogens but porphyry Cu deposits are only associated with hot orogens. Major factors that influence the thermal regime of collisional systems include the rate of continental subduction, the rheology of the underlying lithospheric mantle, the thickness of the overlying lithosphere and radiogenic heat production. Here we propose the removal of suborogenic mantle lithosphere and upwelling of asthenosphere also plays an important role on the thermal structure of collision zones. These processes disturbe the thermal balance of the orogens and cause widespread partial melting of the crust, resulting in the formation of magma-related deposits (i.e., granite-related W-Sn deposits and porphyry Cu deposits). We further give a brief overview of other examples around the globe, such as Pyrenees and Caledonides that reperesent cold orogens versus Variscan and Zagros-Iranian Plateau exemplifying hot orogens.

Automated summary

The thermal regime of collisional orogens plays a crucial role in their evolution, with the Alpine and Himalayan-Tibetan orogens representing cold and hot types, respectively. Major mineral deposit types include Mississippi Valley type Pb-Zn, orogenic gold, and porphyry Cu deposits, with porphyry Cu deposits only associated with hot orogens. Factors influencing the thermal regime of collisional systems include subduction rate, lithospheric mantle rheology, lithosphere thickness, and radiogenic heat production. The removal of suborogenic mantle lithosphere and upwelling of asthenosphere also significantly impact the thermal structure of collision zones.