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鲁西早白垩世镁铁质岩石中有橄榄岩类和辉石岩类捕虏体,前者包括含尖晶石方辉橄榄岩(约占3%)、含铬铁矿纯橄岩(约占95%)和含铬铁矿异剥橄榄岩(约占2%).它们的岩相学、全岩地球化学与矿物地球化学为深俯冲陆壳对相邻岩石圈地幔的改造过程提供了直接证据.含尖晶石方辉橄榄岩主要由橄榄石(82%-89%)、斜方辉石(8%-13%)以及次要的尖晶石(1%-2%)、单斜辉石(-1.5%)和角闪石(-1%)组成,橄榄石的Mg#值介于92.1-93.8之间,其平均值为92.5,橄榄石的δ18O值介于5.5‰-5.6‰之间,全岩的Re亏损模式年龄(TRD)为2.6-2.68 Ga;部分纯橄岩和异剥橄榄岩中的橄榄石具有相对较低的Mg#值(85-90)和较高的δ18O值(6.1‰-7.7‰)以及明显偏高的全岩187Os/188Os比值(0.1269-0.5780).前者代表了鲁西早白垩世期间古老岩石圈地幔的少量残留,后者意味着鲁西早白垩世期间岩石圈地幔的绝大多数已经被改造.费县早白垩世玄武岩中含橄榄石的二辉石岩中可观察到橄榄石被斜方辉石所交代和相继出现的斜方辉石被单斜辉石所交代的改造过程,这与斜方辉石(1097-1491μg/g)和单斜辉石(581-809μg/g)明显富集Ni的地球化学属性相吻合.辉石岩中橄榄石的氧同位素组成(δ18O=7.28‰-8.21‰)和单斜辉石的锶同位素组成(介于0.70862-0.70979之间)表明,改造岩石圈地幔的熔体起源于深俯冲扬子板片的部分熔融.
The Lixi Early Cretaceous mafic rocks contain peridotites and pyroxenite xenoliths, the former including spinel-hzeenite (about 3%), chromite-bearing dunite (about 95% ) And chromite-bearing de-autolitization peridotites (about 2%). Their lithology, whole-rock geochemistry and mineral geochemistry provide direct evidence for the remodeling of the adjacent lithospheric mantle by deep-dive continental crust. The spinel-bearing hardenite is mainly composed of olivine (82% -89%), orthopyroxene (8% -13%) and minor spinel (1% -2% 1.5%) and amphibole (-1%). The Mg # values of olivine ranged from 92.1 to 93.8, the average values were 92.5 and the δ18O values of olivine ranged from 5.5 ‰ -5.6 ‰ The Re depletion mode age (TRD) of rocks is 2.6-2.68 Ga. Olivine in some dunites and dextral peridotites has a relatively low Mg # value (85-90) and a high δ18O value (6.1% o -7.7 ‰), and the 187Os / 188Os ratio (0.1269-0.5780) of the whole rock, which is obviously higher than that of the Lushui Early Cretaceous.The former indicates a small amount of residual of the ancient lithospheric mantle during the Lixi Early Cretaceous, The vast majority of the mantle has been transformed Peridotite, which contains olivine in the basalt, is characterized by the alteration of orthopyroxenes by orthopyroxacite, which is accounted for by orthopyroxenes and by clinopyroxenes, which is related to orthopyroxene (1097 -1491μg / g) and the clinopyroxenes of clinopyroxene (581-809μg / g) obviously enriched in Ni. The oxygen isotopic compositions of olivine (δ18O = 7.28 ‰ -8.21 ‰) and monoclinic The strontium isotope composition of pyroxene (between 0.70862 and 0.70979) suggests that the melt that reformed the lithospheric mantle originated from the partial melting of deep subducted Yangtze sheet.