关键词: 橄榄岩, 温度计, 压力计, 地幔交代作用, 热历史

Abstract: Peridotite xenoliths from the Jericho kimberlite pipe in the Slave Craton in Canada provides a window to investigate composition and thermal structure of the subcontinental lithospheric mantle. Here we summarized the recent progress in thermometers and barometers of mantle rocks, then measured major and trace element concentrations of 9 fresh peridotite xenoliths from the Jericho kimberlite pipe, and calculated their equilibrium temperatures and pressures using different thermometers and barometers. The results indicate that the garnet-orthopyroxene barometer of Nickel and Green (1985) can yield reliable pressure estimates, and two-pyroxene thermometer of Taylor (1998) and clinopyroxene thermometer of Nimis and Taylor (2000) give consistent temperature estimates. Coarse-grained granoblastic spinel-garnet peridotites and garnet peridotites have equilibrium temperatures of 575-843℃ and pressures of 2.4-3.6 GPa. In contrast, prophyroclastic spinel-garnet lherzolite records temperature of 1109℃ and pressure of 5.0 GPa, and probably experienced an early exhumation event from ~156 km to the middle lithospheric depth by kimberlite magmas and the final exhumation by the eruption of the Jericho kimberlite pipe in the Jurassic. The temperatures estimated from the REE-in-garnet-clinopyroxene are higher than the corresponding values from the major-element based thermometers, indicating a cooling history of the lithospheric mantle beneath the Slave Craton. In addition, spinel peridotites preserved the signature of the high-degree partial melting in the shallow mantle, whereas the lower part of the lithospheric mantle have been modified by metasomatism of kimberlite and silicate melts.

Key words: peridotite, thermometer, barometer, mantle metasomatism, thermal history