Latest Permian-Triassic magmatism of the Taimyr Peninsula: New evidence for a connection to the Siberian Traps large igneous province.

This study presents new whole rock major and trace element, Sr-Nd isotopic, petrographic, and geochronologic data for seven latest Permian (Changhsingian)-Late Triassic (Carnian) granitoid intrusions of the northwestern and northeastern Taimyr Peninsula in the Russian High Arctic. U-Pb zircon ages, obtained using secondary ion mass spectrometry (SIMS), sensitive high-resolution ion microprobe (SHRIMP), and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), define the crystallization age of the Taimyr intrusions studied as ranging from ca. 253 Ma to 228 Ma, which suggests two magmatic pulses of latest Permian-Early Triassic and Middle-Late Triassic age. Ar-Ar dating of biotite and amphibole indicate rapid cooling of the intrusions studied, but Ar-Ar ages of several samples were reset by secondary heating and hydrothermal activity induced by the Middle-Late Triassic magmatic pulse. Petrographic data distinguish two groups of granites: syenite-monzonites and granites-granodiorites. Sr-Nd isotopic data, obtained from the same intrusions, show a variation of initial (87Sr/86Sr)i ratios between 0.70377 and 0.70607, and εNd(t) values range between -6.9 and 1.2. We propose that the geochemical and isotopic compositions of the Late Permian-Triassic Taimyr granites record the existence of a magma mush zone that was generated by the two pulses of Siberian Traps large igneous province (LIP) magmatism. [ABSTRACT FROM AUTHOR]