Canada's LITHOPROBE project (collaborative, multidisciplinary geoseience research leads to new understanding of continental evolution)

Abstract

LITHOPROBE is a scientific project of international stature and the largest earth science research project ever undertaken in Canada. It comprises a series of research teams carrying out collaborative, multidisciplinary investigations of the nature and evolution of the Earth's lithosphere in ten carefully selected transects (study areas) on the Canadian landmass and surrounding continental margins. The project began in 1984 and will conclude in 2003 following syntheses of transect studies and a pan-LITHOPROBE synthesis. In this review, three examples - (1) the Late Archean-Paleoproterozoic assembly of northeastern Laurentia, (2) evolution of the Paleoproterozoic Trans-Hudson Orogen, and (3) development of the Mesozoic-Tertiary southern Canadian Cordillera - exemplify the extensive results. (1) In remote Labrador and northern Quebec, tectonic development of northeastern Laurentia occurred from about 2.5 to 1.7 Ga. It involved the convergent northward drift of two Archean cratons, Superior to the west and Nain to the east, and their ultimate collision with the more northerly Rae Province of the Canadian Precambrian Shield. These movements led to the generation of two orogens, initially the more eastern Torngat Orogen and later the New Quebec Orogen. Primary tectonic activity was brought to a close by post-collisional northerly indentation of the Superior craton and reactivation of the Torngat Orogen. (2) In Saskatchewan and Manitoba, the Paleoproterozoic Trans-Hudson Orogen is the best exposed and most complete orogenic belt of a network of such belts formed by collision of older Archean microcontinents. Understanding of its architecture and tectonic history has been changed fundamentally by LITHOPROBE research. This has resulted in a new working model, chronologically well constrained, for tectonic evolution of the orogen between 2.4 and 1.7 Ga. A previously unknown Archean microcontinent has been identified, and the economically important greenstone belt of the Saskatchewan-Manitoba borderland has been revealed to be a collage of oceanic/arc volcanic assemblages that were later intruded and overlain by volcanic, plutonic, and sedimentary rocks. (3) In British Columbia, the much younger (Phanerozoic) orogen of the southern Canadian Cordillera was the first in which the so-called "exotic" terranes were recognized as fundamental building blocks of the continent. Among many contributions, LITHOPROBE studies in the southern Cordillera have shown that terranes observed on the surface are decoupled from their mantle and lower crust and attached as thin flakes to the craton, and that a thin lithosphere underlies the central part of the orogen. LITHOPROBE has brought many benefits to Canada. Other countries may well find that similar, collaborative, multidisciplinary research projects in the earth sciences are comparably beneficial to them.