In situ Re-Os isotope ages of sulfides in Hannuoba peridotitic xenoliths： Significance for the frequently-occurring mantle events beneath the North China Block

In situ Re-Os isotopes of sulfides in peridotitic xenoliths from Cenozoic Hannuoba basalts were analyzed by LAM-MC-ICPMS. The suifides developed two types of occurrences including silicate-enclosed and interstitial. In the enclosed sulfides, 187Os/188Os vary from 0.1124 to 0.1362 and 187Re/188Os from 0.0026 to 1.8027. In the interstitial ones, 187Os/188Os have a range from 0.1174 to 0.1354 and 187Re/188Os from 0.0365 to 1.4469. The oldest age, calculated by TRD for the enclosed sulfides, is 2.1 Ga. An isochron age of 2.3±1.2 Ga is obtained by five grains of enclosed sulfides and primitive mantle. The sulfides used have lower Re-Os isotopic ratio than primitive mantle. Meanwhile, an isochron age of 645±225 Ma is given by all in- terstitial sulfides and the enclosed sulfides with higher Re-Os isotopic ratio due to Re addition after man- tle formation. In addition, the model age of 1.3 Ga recorded by one interstitial sulfide, having similar TDM and TRD, should be meaningful to deep thermal event. The coexistence of different ages, revealed by in situ Re-Os isotope, indicates frequently-occurring mantle events beneath Hannuoba area.

In situ Re-Os isotope ages of sulfides in Hannuoba peridotitic xenoliths: Significance for the frequently-occurring mantle events beneath the North China Block

In situ Re-Os isotopes of sulfides in peridotitic xenoliths from Cenozoic Hannuoba basalts were analyzed by LAM-MC-ICPMS. The suifides developed two types of occurrences including silicate-enclosed and interstitial. In the enclosed sulfides, ¹⁸⁷Os/¹⁸⁸Os vary from 0.1124 to 0.1362 and ¹⁸⁷Re/¹⁸⁸Os from 0.0026 to 1.8027. In the interstitial ones, ¹⁸⁷Os/¹⁸⁸Os have a range from 0.1174 to 0.1354 and ¹⁸⁷Re/¹⁸⁸Os from 0.0365 to 1.4469. The oldest age, calculated by T _RD for the enclosed sulfides, is 2.1 Ga. An isochron age of 2.3±1.2 Ga is obtained by five grains of enclosed sulfides and primitive mantle. The sulfides used have lower Re-Os isotopic ratio than primitive mantle. Meanwhile, an isochron age of 645±225 Ma is given by all interstitial sulfides and the enclosed sulfides with higher Re-Os isotopic ratio due to Re addition after mantle formation. In addition, the model age of 1.3 Ga recorded by one interstitial sulfide, having similar T _DM and T _RD, should be meaningful to deep thermal event. The coexistence of different ages, revealed by in situ Re-Os isotope, indicates frequently-occurring mantle events beneath Hannuoba area. Supported by the National Natural Science Foundation of China (Grant Nos. 40602009 and 40425002) and the Research Foundation for Outstanding Young Teachers, China University of Geosciences, Wuhan (Grant No. CUGQNL0510)