High-grade metamorphism during Archean–Paleoproterozoic transition associated with microblock amalgamation in the North China Craton: Mineral phase equilibria and zircon geochronology

摘要: Abstract Metamorphic regimes in Archean terranes provide important keys to the plate tectonic processes early Earth. The North China Craton (NCC) is one of ancient continental nuclei Asia and recent models propose that cratonic architecture was built through assembly several microcontinental blocks into larger crustal blocks. Here we investigate garnet- pyroxene-bearing granulite facies rocks along periphery Jiaoliao block NCC. garnet-bearing granulites contain peak mineral assemblage garnet + clinopyroxene + orthopyroxene + magnetite + plagioclase + quartz ± biotite ± ilmenite. Mineral phase equilibria computations using pseudosection geothermobarometry suggest P–T condition 800–830 °C 7–8 kbar for metamorphism. Isopleths XMg orthopyroxene XCa garnet another sample containing garnet + orthopyroxene + quartz + magnetite ± fluid yield conditions 860–920 °C 11–14 kbar. Geochemical data show tonalitic granodioritic composition arc-related setting magmatic protoliths these rocks. Zircon LA-ICP-MS analyses well-defined discordia with upper intercept ages 2562 ± 20 Ma (MSWD = 0.94) 2539 ± 21 Ma (MSWD = 0.59) which correlated timing emplacement protolith. A younger group zircons 2449 ± 41 Ma (MSWD = 0.83); N = 6 as (MSWD = 0.83; N = 6) 2480 ± 44 Ma (MSWD = 1.2; N = 9) constrains Lu–Hf dominantly positive eHf(t) values (up 8.5), residence (TDMC) range 2529 2884 Ma, suggesting magma sources from Meso-Neoarchean juvenile components. high temperature medium pressure metamorphism considered have resulted subduction–collision tectonics associated microblock amalgamation NCC at end Archean. Together evidence an adjacent locality, our results correlate predict paired Archean–Proterozoic transition onset modern style tectonics.