Experimental investigation of melts from a carbonated phlogopite Iherzolite : implcations for metasomatism in the continental lithospheric mantle
Experimental investigation of melts from a carbonated phlogopite Iherzolite : implcations for metasomatism in the continental lithospheric mantle
复制标题
DOI：
--
复制
发表时间：
1992-08
影响因子：
3.1
通讯作者：
Y. Thibault;A. D. Edgar;F. Lloyd
中科院分区：
文献类型：
--
作者：
Y. Thibault;A. D. Edgar;F. Lloyd
研究了碳酸化金云母二辉橄榄岩和金云母二辉橄榄岩模型地幔在3.0 GPa时形成的近固相线熔体的组成。在1100℃时，碳酸盐化金云母二辉橄榄岩产生4wt/o的碱性白云质熔体与富含石榴石的金云母二辉橄榄岩共存，而在1225℃时，金云母二辉橄榄岩与含钛金云母二辉橄榄岩平衡地产生7wo/o的含水钾钙硅酸盐熔体。这些熔体与橄榄岩的反应活性在2.0 Gpa和1000℃下测定，碱性白云岩熔体可以将方辉橄榄岩交代成富橄榄石的金云母，渗入到辉绿岩中可能产生含方解石的金云母。方辉橄榄石与含水硅酸盐熔体的相互作用导致单斜辉石和金云母的富集化。提出了大陆裂谷下活动的旋回交代作用模式。碳酸化的金云母二辉橄榄岩层位，最初形成于岩石圈底部，是由热地幔热柱释放的致密碱性流体形成的，随着裂谷作用的进行，它通过熔融、迁移、固化和反应的循环向上迁移。在100千米深处，碳酸化金云母二辉橄榄岩层位的分步熔融依次产生碱性白云质熔体和水合钾质。
The composition of near-solidus melts formed from a model mantle of carbonated phlogopite therzolite and phlogopite lherzolite was investigated at 3.0 GPa. At I100 "C, the carbonated phlogopite lherzolite yielded 4 wto/o of alkaline dolomitic melt coexisting with garnet-rich phlogopite lherzolite, whereas, at 1225 "C, the phlogopite lherzolite produced 7 wo/o of hydrous potassic and calcic silicate melt in equilibrium with titaniferous phlogopite-bearing lherzolite. The reactivity of these melts with peridotite was determined at 2.0 GPa and 1000 'C. Alkaline dolomitic melts can metasomatize harzburgite to olivine-rich phlogopite wehrlite, and infiltration in wehrlite may produce calcite-bearing phlogopite dunite. The interaction of harzburgite with the hydrous silicate melt results in enrichment in clinopyroxene and phlogopite. A model of cyclic metasomatism active beneath a continental rift is proposed. A horizon of carbonated phlogopite lherzolite, originally formed at the base of the lithosphere by the release of dense alkaline fluids from a hot mantle plume, migrates upward by means of cycles of melting, migrating, solidifying, and reacting as rifting progresses. At a depth of 100 km, fractional melting of the carbonated phlogopite lherzolite horizon yields successively an alkaline dolomitic melt and a hydrous potassic