The geotectonic setting, age and mineral deposit inventory of global layered intrusions

Abstract

In the present paper, we have compiled data on 565 layered and differentiated igneous intrusions globally, documenting their (i) location, (ii) age, (iii) size, (iv) geotectonic setting, (v) putative parent magma(s), (vi) crystallisation sequence, and (vii) mineral deposits. Most studied intrusions occur in Russia (98), Australia (72), Canada (52), Finland (37), South Africa (38), China (33), and Brazil (31). Notable clusters of: (i) Archaean intrusions (~ 15%) include those of the McFaulds Lake Area (commonly known as the Ring of Fire, Canada), Pilbara and Yilgarn cratons (Australia), and Barberton (South Africa); (ii) Proterozoic intrusions (~ 56%) include those of the Giles Event and Halls Creek Orogen (Australia), Kaapvaal craton and its margin (South Africa and Botswana), Kola and Karelia cratons (Finland and Russia), and Midcontinent Rift (Canada and USA); and (iii) Phanerozoic intrusions (~ 29%) include those of eastern Greenland, the Central Asian Orogenic Belt (China and Mongolia) and Emeishan large igneous province (China). Throughout geological time, the occurrence of many layered intrusions correlate broadly with the amalgamation and break-up of supercontinents, yet the size and mineral inventory of intrusions shows no obvious secular changes.In our compilation, 337 intrusions possess one or more types of mineral occurrences, including: (i) 107 with stratiform PGE reef-style mineralisation, (ii) 138 with Ni-Cu-(PGE) contact-style mineralisation, (iii) 74 with stratiform Fe-Ti-V-(P) horizons, and (iv) ≥ 35 with chromitite seams. Sill-like or chonolithic differentiated intrusions present in extensional tectonic settings and spanning geological time are most prospective for Ni-Cu-(PGE) mineralisation. In contrast, PGE reef-style deposits are most prevalent in larger, commonly lopolithic intrusions that are generally >1 Ga in age (~ 75%). Stratiform Fe-Ti-V-(P) horizons are most common in the central and upper portions of larger layered intrusions, occurring in the Archaean and Phanerozoic. Approximately 80% of intrusions with chromitite seams are older than 1 Ga and > 50% of them also contain PGE reefs.Based on the distribution of layered intrusions in relatively well explored terranes (e.g., Finland, South Africa, Western Australia), we propose that many layered intrusions remain to be discovered on Earth, particularly in poorly explored and relatively inaccessible regions of Africa, Australia, Russia, Greenland, Antarctica, South America, and northern Canada.