Ophiolites ophiolitic harzburgites

Partly based on the ophiolite record (see Section 2.04.2.2), the refractory degree of abyssal peridotites was tentatively associated with spreading rate (e.g., Boudier and Nicolas, 1985 Nicolas and Boudier, in press). Mildly refractory peridotites after moderate melt extraction degrees (Iherzolites and cpx-harzburgites) would be... [Pg.820]

The harzburgites and dunites from the Oman and Cuba ophiolites show relatively homogenous PM-normalized trace-element patterns characterized by (i) a subtle (Cuba) to significant (Oman)... [Pg.836]

Refractory peridotites harzburgites and dunites. In contrast with the ophiolitic and abyssal... [Pg.839]

Figure 23 Chondrite-normalized abundances of REEs in representative harzburgites from the Oman ophiolite (symbols—whole-rock analyses), compared with numerical experiments of partial melting performed with the Plate Model of Vemieres et al. (1997), after Godard et al. (2000) (reproduced by permission of Elsevier from Earth Planet. Set Lett. 2000, 180, 133-148). Top melting without (a) and with (b) melt infiltration. Model (a) simulates continuous melting (Langmuir et al., 1977 Johnson and Dick, 1992), whereas in model (b) the molten peridotites are percolated by a melt of fixed, N-MORB composition. Model (b) is, therefore, comparable to the open-system melting model of Ozawa and Shimizu (1995). The numbers indicate olivine proportions (in percent) in residual peridotites. Bolder lines indicate the REE patterns of the less refractory peridotites. In model (a), the most refractory peridotite (76% olivine) is produced after 21.1% melt extraction. In model (b), the ratio of infiltrated melt to peridotite increases with melting degree, from 0.02 to 0.19. Bottom modification of the calculated REE patterns residual peridotites due to the presence of equilibrium, trapped melt. Models (c) and (d) show the effect of trapped melt on the most refractory peridotites of models (a) and (b), respectively. Bolder lines indicate the composition of residual peridotites without trapped melt. Numbers indicate the proportion of trapped melt (in percent). Model parameters...

$Figure 23 Chondrite-normalized abundances of REEs in representative harzburgites from the Oman ophiolite (symbols—whole-rock analyses), compared with numerical experiments of partial melting performed with the Plate Model of Vemieres et al. (1997), after Godard et al. (2000) (reproduced by permission of Elsevier from Earth Planet. Set Lett. 2000, 180, 133-148). Top melting without (a) and with (b) melt infiltration. Model (a) simulates continuous melting (Langmuir et al., 1977 Johnson and Dick, 1992), whereas in model (b) the molten peridotites are percolated by a melt of fixed, N-MORB composition. Model (b) is, therefore, comparable to the open-system melting model of Ozawa and Shimizu (1995). The numbers indicate olivine proportions (in percent) in residual peridotites. Bolder lines indicate the REE patterns of the less refractory peridotites. In model (a), the most refractory peridotite (76% olivine) is produced after 21.1% melt extraction. In model (b), the ratio of infiltrated melt to peridotite increases with melting degree, from 0.02 to 0.19. Bottom modification of the calculated REE patterns residual peridotites due to the presence of equilibrium, trapped melt. Models (c) and (d) show the effect of trapped melt on the most refractory peridotites of models (a) and (b), respectively. Bolder lines indicate the composition of residual peridotites without trapped melt. Numbers indicate the proportion of trapped melt (in percent). Model parameters...$

Boudier F. and Nicolas A. (1985) Harzburgite and Iherzolite subtypes in ophiolitic and oceanic environments. Earth Planet. Set Lett. 76, 84-92. [Pg.861]

Edwards S. J. and Malpas J. (1995) Multiple origins for mantle harzburgites examples from the Lewis Hills, Bay of Islands ophiolite, Newfoundland. Can. J. Earth Sci. 32, 1046-1057. [Pg.862]

Gopel C., Allegre C. J., and Xu R.-H. (1984) Lead isotopic study of the Xigaze ophiolite (Tibet) the problem of the relationship between magmatites (gabbros, dolerites, lavas) and tectonites (harzburgites). Earth Planet. Sci. Lett. 69, 301-310. [Pg.863]

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