T70 Recent Advances in Supercontinents: Paleogeography, Geodynamics, and Paleoclimate Evolution I

Tuesday, 27 October 2020
1:30 PM - 5:30 PM
Meeting Rooms

INSIGHT INTO THE MAGMATIC SYSTEM OF A RECONSTRUCTED LARGE IGNEOUS PROVINCE AT 2.11 GA ACROSS SUPERCRATON SUPERIA

Paper number: T70-11
Program: Technical Sessions
Time: 3:50 PM – 4:05 PM

Authors

Abstract

Supercraton Superia existed between 2.65 and 2.00 Ga, producing a yet unknown number (~5-10?) of Archean crustal fragments that dispersed across the globe after its breakup. Of the known Archean fragments, Superior, Hearne, Wyoming and Karelia-Kola are central to the paleogeographic reconstruction of Superia. Their relative positioning in Superia is partly based on the large igneous province (LIP) record, including at least five Paleoproterozoic LIP matches. Of these LIPs, ca. 2.11 Ga mafic dykes, sills and volcanic rocks represent one of the more prolific magmatic events across Superior, Hearne, Wyoming and Karelia-Kola. In further support of a temporal link between Karelia-Kola and Superior, we present a high-precision U-Pb ID-TIMS zircon dyke age of 2114 Ma from Karelia. If these ca. 2.11 Ga mafic rocks were formed by the same LIP then we may find matching geochemical signatures in some or all of the mafic units located within formerly adjacent cratons.

We compare and model geochemical data of ca. 2.11 Ga mafic rocks using whole-rock major and trace elements, and Nd isotopic results from the Marathon dykes (Superior), Griffin sills and Kazan dykes (Hearne), Bear Mountain dykes (Wyoming), and Tohmajärvi dykes as well as Oravaara and Hirsimaa volcanic rocks (Karelia-Kola). Four geochemical groups are identified, most of which are found across multiple cratons. These include two groups representing distinct mantle end-members: Group 1 is similar to mid-ocean ridge basalt and confined to Karelia-Kola, and Group 2 has an ocean island basalt composition and is found in Hearne, Wyoming and Karelia-Kola. Modeled by bulk mixing, Group 3 is a hybrid of Groups 1 and 2. Groups 1, 2 and 3 underwent variable degrees of assimilation and fractional crystallization to form Group 4 – the most common and extensive of all geochemical groups.

Integration of contemporaneous geochemistry from across Superior, Hearne, Wyoming and Karelia-Kola has identified exact geochemical matches and enabled the development of a holistic plumbing system model for ca. 2.11 Ga mafic units. Overall, this analysis supports the shared petrogenesis of ca. 2.11 Ga mafic units from Superior, Hearne, Wyoming and Karelia-Kola within the context of the Superia supercraton paleogeographic reconstruction.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-354664

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