The formation of three-grain junctions during solidification. Part II: theory
The formation of three-grain junctions during solidification. Part II: theory
复制标题
凝固过程中三晶粒结的形成。
DOI：
10.1007/s00410-022-01921-w
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发表时间：
2022
影响因子：
3.5
通讯作者：
Fowler A
中科院分区：
文献类型：
--
作者：
Fowler A
结晶岩石中颗粒交界处的热力学平衡二面角由晶界界面表面能决定，但达到平衡所需的较长时间意味着火成岩中观察到的二面角一般由结晶动力学决定。我们在镁铁质火成岩中区分出三种类型的辉石-斜长石-斜长石二面角。在第一种情况下，辉石生长在先前存在的斜长石骨架的孔隙中，伴随着斜长石孔壁的很少或没有向内生长。在第二种情况下，斜长石孔壁与辉石同时向内生长，除撞击角较大外，二面角一般都大于两斜长石颗粒的原始撞击角度。第一种是在快速结晶的岩石中看到的，而第二种是在缓慢冷却的岩石中观察到的。第三种是高度不对称的，类似于(所以我们称之为)鹰喙：只有在缓慢冷却的岩石中才能看到。它在辉长岩堆积岩中很常见，也存在于强烈正堆积托托岩中。用间隙相模式计算了朗姆和斯卡尔加德层状侵入体中一系列镁铁质堆积体中存在的间隙液体的数量，结果表明，随着岩石从堆积到正堆积(即随着橄榄石-斜长石晶体碎屑变得更加富液)，闪长岩中三粒结的不对称性增加，鹰喙成为含∼12vol.%间隙物质(相当于∼30vol.%液体在碎屑中)的闪长质熔块的主要三粒结几何形状。因此，镁铁质岩石中三粒结的几何形状不仅是冷却速度的函数，也是分馏过程中沿液体下降线的进程的函数。前两种类型的结点形成于相对原始的液体中，在此期间，凝固岩浆体边缘的结晶泥主要由斜长石和橄榄石形成，而一旦辉石形成堆积岩浆中晶体骨架的重要组成部分，要么因为它是形成骨架的原晶相，要么因为它来自高度丰富的间隙液体，就会出现鹰嘴几何形状。
The thermodynamic equilibrium dihedral angle at grain junctions in crystalline rocks is set by the grain boundary interfacial surface energies, but the long times required to attain equilibrium mean that the observed dihedral angles in igneous rocks are generally set by the kinetics of crystallisation. We distinguish three types of augite–plagioclase–plagioclase dihedral angle in mafic igneous rocks. In the first, augite grows in the pores of a pre-existing plagioclase framework accompanied by little to no inwards-growth of the plagioclase pore walls. In the second, the plagioclase pore walls grow inwards simultaneously with the augite, and the dihedral angle is generally larger than the original angle at which the two plagioclase grains impinged except when the impingement angle itself is large. The first type is seen in rapidly crystallised rocks, whereas the second is observed in slowly cooled rocks. The third type is highly asymmetric and resembles (and so we call) an eagle’s beak: it is only seen in slowly cooled rocks. It is common in gabbroic cumulates, and is also present in strongly orthocumulate troctolites. Using the mode of interstitial phases to calculate the amount of interstitial liquid present in a series of mafic cumulates from the Rum and Skaergaard layered intrusions, we show that the asymmetry of three-grain junctions in troctolites increases as the rocks progress from adcumulate to orthocumulate (i.e. as the olivine–plagioclase crystal mush becomes more liquid-rich), with eagles’ beaks becoming the dominant three-grain junction geometry for troctolitic mushes containing ∼ 12 vol.% interstitial material (corresponding to ∼ 30 vol.% liquid in the mush). The geometry of three-grain junctions in mafic rocks is thus a function not only of cooling rate, but also of the progression along the liquid line of descent during fractionation. The first two types of junction are formed in relatively primitive liquids, during which the crystal mushes on the margins of the solidifying magma body are formed predominantly of plagioclase and olivine, whereas the eagle’s beak geometry occurs once augite forms an important component of the crystal framework in the accumulating mush, either because it is a framework-forming primocryst phase or because it grows from highly abundant interstitial liquid.
斜长石生长速率控制辉长岩和辉长岩中的三晶粒连接几何形状
DOI：
--
发表时间：
2015
期刊：
影响因子：
--
作者：
M. Holness
通讯作者：
M. Holness
非线性扩散方程中的等待时间行为
DOI：
--
发表时间：
1982
期刊：
影响因子：
--
作者：
W. Kath;D. Cohen
通讯作者：
D. Cohen