Aragonite in olivine from Calatrava, Spain-Evidence for mantle carbonatite melts from >100 km depth
Aragonite in olivine from Calatrava, Spain-Evidence for mantle carbonatite melts from >100 km depth
复制标题
西班牙卡拉特拉瓦橄榄石中的文石——超过 100 公里深度的地幔碳酸盐岩熔融的证据
作者：
Humphreys E
文石作为来自白榴石熔岩流的橄榄石中的内含物，为西班牙卡拉特拉瓦地球物理岩石圈下的高压结晶和碳酸岩活动提供了证据。文石以橄榄石 (Fo87) 内的单晶形式出现，被解释为是从地幔深处的碳酸盐硅酸盐熔体中结晶出来的。实验数据将文石的稳定性限制在 >100 km 深度、含 CO2-H2O 的地幔固相线温度下。这是岩浆文石在地幔中结晶的第一个有记录的证据。橄榄石以异晶的形式夹带，并未从载体熔体中结晶出来，而载体熔体一定是在地幔深处形成的。白榴石和碳酸盐包裹体的铅同位素数据表明，相对于大洋中脊玄武岩和大多数洋岛玄武岩，源熔体显示出同位素富集。我们的证据强化了在含有玛珥型火山活动的碱性火山省（如卡拉特拉瓦）中直接和深部地幔衍生的火山碳酸岩的论点。
Aragonite, as an inclusion in olivine from a leucitite lava flow, provides evidence for high-pressure crystallization and carbonatitic activity beneath the geophysical lithosphere in Calatrava, Spain. The aragonite occurs as a single crystal within olivine (Fo87), interpreted to have crystallized from a carbonated silicate melt at mantle depths. Experimental data constrain the stability of aragonite to depths of >100 km at CO2-H2O-bearing mantle solidus temperatures. This is the first documented evidence of magmatic aragonite crystallized in the mantle. Entrained as xenocrysts, the olivines have not crystallized from the carrier melts, which must have formed deeper within the mantle. Lead isotope data of the leucitite and carbonate inclusions indicate that the source melts show isotopic enrichment relative to mid-oceanic ridge basalt and most ocean island basalt. Our evidence strengthens the argument for direct and deep mantle-derived volcanic carbonatite in alkaline volcanic provinces containing maar-type volcanism, such as Calatrava.