近日，华东理工大学Leng, Chengbiao团队研究了西昆仑造山带石炭系奥塔格岩体热态的锆石结构和元素证据。该项研究成果发表在2025年12月17日出版的《地球化学学报》杂志上。

研究组对中国西北西昆仑造山带石炭纪奥依塔格岩体中的锆石，提供了新的阴极发光图像与微量元素数据。他们在同一奥长花岗岩体中识别出反映平衡与非平衡晶体生长的振荡环带与扇形分带锆石。振荡环带锆石的铪含量（10,638–13,648 ppm）与钛含量（1.95–4.18 ppm）呈负相关，揭示了分离结晶作用在岩浆演化中的主导地位。相比之下，扇形分带锆石表现出与铪含量（8,951–10,085 ppm）无关的剧烈变化钛含量（0.72–6.07 ppm），这可能反映了快速冷却过程。

在快速生长与高度过冷条件下，相容元素（如铪）未能有效进入晶格，而不相容元素（如铌）未能及时从结晶前沿排出。浅色柱状生长区的铪/铌比值高于深色锥状生长区，但与平衡振荡环带锆石的该比值范围重叠。这表明浅色柱状生长区比深色锥状生长区更接近与熔体的平衡状态。研究组认为扇形分带与振荡环带锆石的形成，分别对应奥依塔格岩体边缘与内部区域的快速冷却与缓慢冷却过程。进一步推断，在奥依塔格弧后盆地发育过程中，早期小型岩浆系统可能比晚期形成的岩浆系统以更快的冷却速率凝固。

附：英文原文

Title: Zircon textural and elemental evidence for the thermal state of the Carboniferous Oytag pluton in the West Kunlun Orogenic Belt, northwest China

Author: Yu, Bingjin, Wang, Yanjun, Wei, Ying, Wang, Shuilong, Xu, Chuanlong, Wu, Chengquan, Zhu, Weiguang, Leng, Chengbiao

Issue&Volume: 2025-12-17

Abstract: This study presents new cathodoluminescence images and trace element data for zircon from the Carboniferous Oytag pluton in the West Kunlun Orogenic Belt, northwest China. We identify oscillatory and sector-zoned zircon grains that reflect equilibrium and disequilibrium crystal growth within the same trondhjemite pluton. The oscillatory zircon grains display negative correlations between Hf (10,638–13,648 ppm) and Ti (1.95–4.18 ppm) contents, highlighting the dominating role of fractionation in evolving magmas. In contrast, the sector-zoned zircon grains exhibit highly variable Ti contents (0.72–6.07 ppm) uncorrelated with Hf (8951–10,085 ppm), likely reflecting rapid cooling. At a fast growth rate with high undercooling, compatible elements (e.g., Hf) are not efficiently incorporated into the crystal lattice, while incompatible elements (e.g., Nb) are not promptly removed from the crystallizing front. Hf/Nb ratios in the light prismatic sectors are higher than those in the dark pyramidal sectors but overlap with those in the equilibrium oscillatory zircon. It is suggested that the light prismatic sectors are closer to the equilibrium with melts than dark pyramidal sectors. We attribute the formation of sector-zoned and oscillatory zircon to fast and slow cooling rates at the margin and interior of the Oytag pluton, respectively. We further infer that early, small magmatic systems may solidify at faster cooling rates than their postdating counterparts during the development of the Oytag back-arc basin.

DOI: 10.1007/s11631-025-00841-3

Source: https://link.springer.com/article/10.1007/s11631-025-00841-3