Brittle fracturing and fracture healing of zircon: An integrated cathodoluminescence, EBSD, U-Th-Pb, and REE study
Brittle fracturing and fracture healing of zircon: An integrated cathodoluminescence, EBSD, U-Th-Pb, and REE study
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DOI：
10.2138/am.2007.2458
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发表时间：
2007-07
影响因子：
3.1
通讯作者：
A. Rimša;M. Whitehouse;L. Johansson;S. Piazolo
中科院分区：
文献类型：
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作者：
A. Rimša;M. Whitehouse;L. Johansson;S. Piazolo
摘要瑞典西南部Tjärnesjö侵入体的混合花岗岩中的岩浆振荡环带锆石的整个种群揭示了精细尺度的脆性断裂。振荡分区碎片旋转但不分散。个别碎片之间的裂缝被新形成的CL-明亮锆石封闭。水力压裂是最有可能的机制。断裂锆石的内部结构和CL-亮锆石的LREE富集、低Th特征都表明，振荡环带锆石碎片之间的裂纹在断裂后被从热液流体中沉淀的CL-亮锆石快速封闭。用西姆斯离子探针和U-Th-Pb同位素测得的锆石破裂和裂缝封闭年龄为920 ± 51 Ma（下截距年龄，2σ，MSWD = 1.09），最小可能年龄为960 ± 16 Ma（207 Pb/206 Pb，2σ，MSWD = 0.23），由在破裂核上形成的扇形环带边缘确定。
Abstract The entire population of magmatic oscillatory zoned zircons in a migmatitic granite from the Tjärnesjö intrusion, southwest Sweden, reveal fine-scale brittle fracturing. The oscillatory zoned fragments are rotated but not dispersed. Fractures between individual fragments are sealed by newly formed CL-bright zircon. Hydraulic fracturing is the most probable mechanism. The internal structure of fractured zircons and the LREE-enriched, low Th character of CL-bright zircon both suggest that cracks between oscillatory zoned zircon fragments were rapidly sealed after fracturing by CL-bright zircon, precipitated from hydrothermal fluids. Zircon fracturing and crack-sealing has been dated by SIMS ion-probe and U-Th-Pb isotopes to 920 ± 51 Ma (lower intercept age, 2σ, MSWD = 1.09) with a limit for the youngest possible age of 960 ± 16 Ma (207Pb/206Pb, 2σ, MSWD = 0.23) dated by sector-zoned rims forming overgrowths on the fractured cores.