--> Abstract: Insights on the Origin of the Crockerland Terrane: U-Pb, Hf, and He Detrital Zircon Data from the Canadian Arctic Islands, by Owen Anfinson; #90177 (2013)

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Insights on the Origin of the Crockerland Terrane: U-Pb, Hf, and He Detrital Zircon Data from the Canadian Arctic Islands

Owen Anfinson

Geochronologic data from strata of the Franklinian Basin of the Canadian Arctic Islands provide insight on the origin and geologic nature of a continental fragment (Crockerland) that collided with the northern Laurentian margin during the Devonian to Mississippian Ellesmerian Orogeny. The existence of a terrane that lay north of the modern arctic margin from the Devonian to Middle Jurassic is well documented in the literature, however the origin of this terrane remains poorly constrained. Detrital zircons transported from Crockerland into the Franklinian Basin provide information on the paleogeographic location of Crockerland prior to its accretion to northern Laurentia. Detrital zircon U-Pb ages from Late Devonian sandstones of the Franklinian Basin yield populations of 360-480, 510-710, 940-1270, 1310-2100, and minor 2300-2900 Ma. These sandstones are interpreted to have northern source region based on detrital composition, paleocurrent indicators, Nd values and exotic detrital zircon populations. The U-Pb ages are augmented with εHf data and He ages from the same zircon separates. εHf values were obtained from detrital zircon U-Pb age populations of 380–450, 520–550, and 650–710 Ma. The εHf values suggest the zircons are derived from a relatively juvenile lithosphere. εHf values of 7.3 (380–400 Ma) and 2.1 (420–450) Ma indicate the zircons of this age are primarily derived from either an island arc or continental arc built on accreted oceanic crust. Detrital zircon He ages from the Late Devonian sandstones are older than corresponding stratigraphic ages indicating they have not been reset during subsequent burial, thus the ages record exhumation of the source terrane. The detrital zircon He ages contain a prominent population of 420-430 Ma, suggesting considerable exhumation of the Crockerland terrane during the Caledonian Orogen. The U-Pb, εHf and He data suggest the Crockerland terrane had a complex geologic framework and indicate involvement of the terrane in the Caledonian, Timanian and Grenvillian Orogens. Links to the Caledonian, Timanian, and Grenvillian orogens strongly suggest Crockerland originated to the east (modern orientation) of northern Laurentia. The suggested origin of Crockerland fits well with paleogeographic reconstructions depicting the westward migration of numerous terranes during the closure of the northern Iapetus Ocean and the extrusion of these terranes along the northern Laurentian margin after the continent-continent collision of Laurentia and Baltica during the Scandian phase of the Caledonian Orogen.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013