Ultrabasic magmas and high-degree melting of the mantle
Ultrabasic magmas and high-degree melting of the mantle
复制标题
超基性岩浆与地幔高度熔融
DOI：
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发表时间：
1977
期刊：
影响因子：
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通讯作者：
N. Arndt
中科院分区：
文献类型：
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作者：
N. Arndt
随着地幔橄榄岩熔化程度的增加，形成的液体变得更加碱性且粘度降低，并且残余晶体之间的间距增加。因此，随着液体比例从 15% 增加到 60%，部分熔体中残余晶体的沉降速度将增加几个数量级，对于 1 cm 橄榄石颗粒，从 9.4 × 10−4 cm/s 增加到 4.3 × 10−1 cm/s。要从具有通常假设的地幔成分的源中产生超基性科马提质岩浆，需要 50% 到 80% 的熔化。在达到这种程度的熔化之前，由 30% 至 50% 熔化产生的高流动性苦苦参岩浆将从源头分离出来。超基性岩浆可能是通过连续的熔融过程形成的，并且源自由难熔矿物和先前部分熔融和岩浆提取留下的滞留液体组成的残留物。超基性科马提岩熔岩中的微量元素浓度与这一理论一致。
As the degree of melting of mantle peridotite increases, the liquids that are formed become more basic and less viscous, and the spacing between residual crystals increases. The settling velocities of residual crystals in partial melts consequently will increase by several orders of magnitude, from 9.4 × 10−4 cm/s to 4.3 × 10−1 cm/s for a 1 cm olivine grain, as the proportion of liquid increases from 15 to 60%.To produce an ultrabasic komatiitic magma from a source with commonly assumed mantle composition requires 50 to 80% melting. Before this degree of melting can be reached, a highly fluid picritic magma produced by 30 to 50% melting will segregate from the source. Ultrabasic magmas probably form by a sequential melting process and are derived from a residuum composed of refractory minerals and trapped liquid left by previous episodes of partial melting and magma extraction. Trace element concentrations in ultrabasic komatiite lavas are consistent with this theory.