Controls on trace-element partitioning among co-crystallizing minerals: Evidence from the Panzhihua layered intrusion, SW China
Controls on trace-element partitioning among co-crystallizing minerals: Evidence from the Panzhihua layered intrusion, SW China
复制标题
共晶矿物间微量元素分配的控制：来自中国西南攀枝花层状岩体的证据
DOI：
10.2138/am-2017-5804
复制
发表时间：
2017-05
影响因子：
3.1
通讯作者：
Xie Wei
中科院分区：
文献类型：
--
作者：
Chen Lie-Meng;Song Xie-Yan;Hu Rui-Zhong;Yu Song-Yue;He Hai-Long;Dai Zhi-Hui;She Yu-Wei;Xie Wei
摘要在层状侵入体中，控制共结晶堆积矿物中微量元素分配的因素和过程长期以来一直存在争议。本文利用来自峨眉山大火成岩省攀枝花层状侵入体的磁铁矿、钛铁矿和单斜辉石的激光消融电感耦合等离子体质谱(ICPMS)新的微量元素数据来解决这个问题。堆积矿物表现出强烈的镍、钴和铬亏损，表明母岩浆中这些元素的浓度较低，这可能是由于先前硫化物的去除以及深部阶段性岩浆室中铬铁矿或铬磁铁矿的分馏所致。磁铁矿和单斜辉石的某些过渡元素(如铬、钒、镍)沿地层剖面呈周期性变化。这些过渡元素在磁铁矿中的平均浓度与在单斜辉石中的平均浓度呈正相关，可能是磁铁矿和单斜辉石共结晶的结果。下层堆积体矿物的不相容元素(如：Zr、Hf、Nb)的浓度与中部和上部带的不相容元素浓度差异很大。这些微量元素组成的巨大变化归因于下部带的“俘获液体移动”。攀枝花侵入体中的钛铁矿晶体在与磁铁矿的固相线下重新平衡过程中可能发生了过渡元素的大量变质，导致钛铁矿过渡元素在下带地层中的解耦变化。我们的研究表明，需要考虑主要堆积矿物组合的系统微量元素变化，而不是单一矿物，以更好地约束岩浆分异和层状侵入体的元素分馏。
Abstract The factors and processes that control trace-element partitioning among co-crystallizing cumulus minerals in layered intrusions have long been controversial. Here we address this issue using new laser ablation ICP-MS trace element data for magnetite, ilmenite, and clinopyroxene from the Panzhihua layered intrusion in the Emeishan large igneous province, SW China. The cumulus minerals display strong Ni, Co, and Cr depletions, indicative of parental magmas low in concentration of these elements probably due to prior sulfide removal and the fractionation of chromite or Cr-magnetite in a staging magma chamber at depth. Both magnetite and clinopyroxene show cyclical variations in some transition elements (e.g., Cr, V, and Ni) along the stratigraphic section. The average concentrations of these transition elements in magnetite are positively correlated with those in clinopyroxene, likely resulting from co-crystallization of magnetite and clinopyroxene. The incompatible element (e.g., Zr, Hf, and Nb) concentrations of the cumulus minerals from the Lower Zone are highly variable compared to those of the Middle and Upper Zones. These large variations in trace element compositions are attributed to a “trapped liquid shift” in the Lower Zone. Ilmenite crystals from the Panzhihua intrusion may have undergone extensive modification of transition elements during subsolidus re-equilibration with magnetite, leading to the decoupled variations of transition elements in ilmenite across the Lower Zone stratigraphy. Our study indicates that systematic trace element variations of the main cumulus mineral assemblage, rather than a single mineral, need to be considered to better constrain the magmatic differentiation and elemental fractionation of layered intrusions.
登录
查看更多内容
影响因子：
1.8
作者：
Zhang Xiao
通讯作者：
Zhang Xiao
影响因子：
--
作者：
B. Frost;D. Lindsley
通讯作者：
B. Frost;D. Lindsley
影响因子：
6.1
作者：
J. Shellnutt;S. Denyszyn;R. Mundil
通讯作者：
J. Shellnutt;S. Denyszyn;R. Mundil
影响因子：
3
作者：
Yuwei She;Xie‐Yan Song;Songyue Yu;Haijiang He
通讯作者：
Yuwei She;Xie‐Yan Song;Songyue Yu;Haijiang He
影响因子：
5.8
作者：
Yigang Xu;B. He;Sun‐Lin Chung;M. Menzies;F. Frey
通讯作者：
Yigang Xu;B. He;Sun‐Lin Chung;M. Menzies;F. Frey