文档介绍：Chapter 4
Open-system Melting
Chapters 1 to 3 consider melting and melt extraction. In this chapter, we
further take into account input of materials into the melting zone.
Melting in the crust and the mantle sometimes can be a open-system
process (Navon and Stolper, 1987; Iwamori, 1993; O'Hara, 1995; Ozawa
and Shimizu, 1995; Spiegelman, 1996; Vernieres et al., 1997; Zou, 1998;
Shaw, 2000). Ozawa and Shimizu (1995) proposed a quantitative open-
system melting model to explain the trace element patterns in ophiolites
from a volcanic arc environment where fluid enters into the melting
zone. Shaw (2000) suggested that, in addition to fluid, solid may enter
into the melting zone. Besides volcanic arc environment, the addition of
fluid and solid into the melting zone may take place in other tectonic
settings. Melting below continents may be often related to fluid addition.
In this chapter, we discuss models for open-system batch melting and
open-system dynamic melting.
-system Batch Melting (OBM)
. OBM with one-time instantaneous addition of melt
The one-time addition of fluids can be regarded as a one-time fluid
metasomatism of the solid rocks just as it starts melting. This is a
potential important model for mantle metasomatism.
The mass balance of the total mass gives
Mf+M, =M,+M,,
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Open-system Melting 61
where M, is the mass of the melt, M, is the mass of the solid, M, the
mass of the source before melting, and Mu the mass of the added melt.
The balance of the mass of an element requires
C, M ,+ C, M = C,M, + CUM,, ()
,~
where C, is the concentration of an element in the melt, C,y is the
concentration in the solid, C, is the concentration in the source before
melting, and C, is the concentration in the added melt.
The amount of one-time fluid metasomatism is related to the mass of the
melting zone source rocks by
Mu= WM, . ()
Note that Mu is independent of F in this one-