Anhydrous PT phase relations of an Aleutian high-MgO basalt: an investigation of the role of olivine-liquid reaction in the generation of arc high-alumina basalts
Anhydrous PT phase relations of an Aleutian high-MgO basalt: an investigation of the role of olivine-liquid reaction in the generation of arc high-alumina basalts
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DOI：
10.1007/bf00310781
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发表时间：
1992-12
影响因子：
3.5
通讯作者：
D. Draper;A. Johnston
中科院分区：
文献类型：
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作者：
D. Draper;A. Johnston
我们报道了对ID16的无水1大气压和活塞-圆柱体实验的结果，ID16是一种阿留申高镁玄武岩(HMB)，旨在研究弧形高铝玄武岩(HABS)和不常见的HMBS之间的潜在岩石成因联系。ID16与斜长石/尖晶石二辉橄榄石矿物组合(橄榄石、斜长石、单斜辉石、斜辉石、尖晶石)在12kbar的液线下多次饱和。在ID16的10-20kbar熔融区间内的高温下产生的衍生液体的成分与许多中CaO HABS公布的成分相似，尽管较低温度的液体比典型HABS的CaO含量更低，碱的含量更丰富。等摩尔拟三元推算和数值质量平衡模拟表明，ID16的衍生熔体在10kbar和1,200°C-1,150°C时与橄榄石进入复杂的反应关系。我们试图测试这样的机制来解释在SSS等镁铁质高铝玄武岩的无水实验中缺少液橄榄石的原因。1.4(约翰斯顿1986年)。然而，这些衍生液体与典型的弧形高铝玄武岩并不相似，这表明橄榄石-液体反应不能解释Johnston(1986)的观察。相反，我们认为橄榄石只有通过水的参与才能被带到这种成分的液相线上，这将在低于∼12kbar的压力下影响CaO、MgO和Al_2O_3的体积含量对HAB液相线相(橄榄石或斜长石)的识别的影响。
We report results of anhydrous 1 atm and piston-cylinder experiments on ID16, an Aleutian high-magnesia basalt (HMB), designed to investigate potential petrogenetic links between arc high-alumina basalts (HABs) and less common HMBs. ID16 is multiply saturated with a plagioclase/spinel iherzolite mineral assemblage (olivine, plagioclase, clinopyroxene, orthopyroxene, spinel) immediately beneath the 12 kbar liquidus. Derivative liquids produced at high temperatures in the 10–20 kbar melting interval of ID16 have compositions resembling those published of many moderate-CaO HABs, although lower-temperature liquids are poorer in CaO and richer in alkalies than are typical HABs. Isomolar pseudoternary projections and numerical mass-balance modeling suggest that derivative melts of ID16 enter into a complex reaction relationship with olivine at 10 kbar and 1,200° C–1,150° C. We sought to test such a mechanism to explain the lack of liquidus olivine in anhydrous experiments on mafic high-alumina basalts such as SSS. 1.4 (Johnston 1986). These derivative liquids, however, do not resemble typical arc high-alumina basalts, suggesting that olivine-liquid reaction does not account for Johnston's (1986) observations. Instead, we suggest that olivine can be brought onto the liquidus of such compositions only through the involvement of H2O, which will affect the influence of bulk CaO, MgO, and Al2O3contents on the identity of HAB liquidus phases (olivine or plagioclase) at pressures less than ∼12 kbar.