Melting wedge

In many practical situations involving the flow of polymer melts through dies and along channels, the cross-sections are tapered. In these circumstances, tensile stresses will be set up in the fluid and their effects superimposed on the effects due to shear stresses as analysed above. Cogswell has analysed this problem for the flow of a power law fluid along coni-cylindrical and wedge channels. The flow in these sections is influenced by three factors ... 

In this technique the concentration of a drug in an agar plate may (theoretically) be varied infinitely between zero and a given maximum. To perform the test, nutrient agar is melted, the solution under test added, and the mixture poured into a sterile Petri dish and allowed to set in the form of a wedge (Fig. 11.6A). 

In summary, there is permissive evidence that the sedimentary component is added to the mantle wedge before the fluid addition and melting that leads to arc magmatism. 

In contrast to the southern volcanic zone, Parinacota volcano lies on very thick continental crust (> 70 km) in the central volcanic zone of Chile. Bourdon et al. (2000a) showed that young Parinacota lavas encompass a wide range of U-Th disequilibria. excesses were attributed to fluid addition to the mantle wedge but °Th-excesses in lavas from the same volcano are more difficult to explain. The lavas with °Th-excesses also have low ( °Th/ Th) (< 0.6) characteristic of lower continental crust characterized by low Th/U and in their preferred model. Bourdon et al. (2000a) attributed the °Th-excesses to contamination by partial melts, formed in the presence of residual garnet, of old lower crustal materials. 

Woodhead J, Eggins S, Gamble J (1993) High field strength and transition element systematics in island arc and back-arc basin basalts evidence for multi-phase melt extraction and a depleted mantle wedge. Earth Planet Sci Lett 114 491-504... 

This section describes the continuous flux melting model used in Bourdon et al. (2003) and has many similarities with the model of Thomas et al. (2002). A significant difference is that the model described here keeps track of the composition of the slab as it dehydrates. This model is based on mass balance equations for both the mantle wedge and the slab. We assume secular equilibrium in the U-series decay chain initially ... 

At each step, a fraction of fluid f is added to the mantle wedge from the slab. The bulk partition coefficients used for fluid dehydration can be derived from published mineral/fluid partition coefficients (see Tables Al and A2). The composition of the residual slab is estimated as follows after At which is the time step between two melt extractions (similar equation for Th and Pa) ... 

We assume that a constant mass fraction fr remains in the mantle wedge after melt extraction. As in Section A2 of the Appendix, the ratio of slab mass to wedge mass is assumed to be equal to 1 but more complex models are also possible. The bulk composition of the mantle wedge after melt extraction is calculated with the following equation after each extraction increment ... 

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