Nb/Ta systematics in arc magma differentiation and the role of arclogites in continent formation
Nb/Ta systematics in arc magma differentiation and the role of arclogites in continent formation
复制标题
DOI：
10.1038/s41467-018-08198-3
复制
发表时间：
2019-01
影响因子：
16.6
通讯作者：
Ming Tang;Cin-Ty A. Lee;Kang Chen;Monica Erdman;G. Costin;Hehe Jiang
中科院分区：
文献类型：
--
作者：
Ming Tang;Cin-Ty A. Lee;Kang Chen;Monica Erdman;G. Costin;Hehe Jiang
岩石行星的表面大部分被玄武质地壳覆盖，但地球的独特之处在于它也有大面积的长英质地壳区域，以大陆的形式表现出来。当玄武岩岩浆是岩石行星地幔融化的主要产物时，长英质地壳究竟是如何形成的尚不清楚。争论的一个基本部分集中在与玄武岩 (15-16) 相比，地球大陆地壳 (11-13) 的 Nb/Ta 含量较低。在这里，我们发现，在弧岩浆分异过程中，Nb/Ta 分异程度随地壳厚度的变化而变化，在大陆弧岩浆中观察到最低的 Nb/Ta。由于存在高 Nb/Ta 岩浆金红石，深弧堆积物（弧辉岩）被发现具有高 Nb/Ta（平均~19）。我们表明，Nb/Ta 的地壳厚度控制可以通过较高压力下有利于金红石饱和度来解释。因此，深层岩浆分异，例如大陆弧和其他岩浆造山带中的岩浆分异，对于形成大陆是必要的。
The surfaces of rocky planets are mostly covered by basaltic crust, but Earth is unique in that it also has extensive regions of felsic crust, manifested in the form of continents. Exactly how felsic crust forms when basaltic magmas are the dominant products of melting the mantles of rocky planets is unclear. A fundamental part of the debate is centered on the low Nb/Ta of Earth’s continental crust (11–13) compared to basalts (15–16). Here, we show that during arc magma differentiation, the extent of Nb/Ta fractionation varies with crustal thickness with the lowest Nb/Ta seen in continental arc magmas. Deep arc cumulates (arclogites) are found to have high Nb/Ta (average ~19) due to the presence of high Nb/Ta magmatic rutiles. We show that the crustal thickness control of Nb/Ta can be explained by rutile saturation being favored at higher pressures. Deep-seated magmatic differentiation, such as in continental arcs and other magmatic orogens, is thus necessary for making continents.