日本国家极地研究所Tomoaki Morishita研究团队报道了一个长寿的镁铁质岩浆库，从角闪石橄榄岩中获取锆石证据。这一研究成果发表在2023年10月11日出版的国际学术期刊《地质学》上。

研究小组报道了来自日本Hida带角闪岩橄榄岩中锆石的OUPb年龄、地球化学和HfO同位素数据，为研究弧环境中长寿命的镁质管道系统的寿命提供了独特的机会。该课题组研究人员找到了两个锆石UPb年龄测定仪:196 Ma不相容富元素测定仪和186 Ma不相容贫元素测定仪。它们的同位素特征(δ18O = 7.7‰±0.8‰，εHf = 10.3‰±1.7‰)均表明，尽管存在10 m.y的年龄差距，岩浆强度是相同的。

不同的锆石形成机制决定于锆石饱和是否需要高SiO2分异熔体。富集的较老锆石是由基性熔体-橄榄石界面局部锆石饱和形成的，而较年轻的贫锆石则是由与角闪石共存的间隙长英质熔体的沉淀而成。他们的发现证实了下火山口岩浆系统的寿命，这表明了跨火山口岩浆系统和火山口演化。

据介绍，锆石年代学有助于他们理解穿心岩浆系统的寿命。然而，由于锆石在基性-超基性岩中的产状有限，研究大多集中在长英质岩中的锆石记录上。

附：英文原文

Title: A long-lived mafic magma reservoir: Zircon evidence from a hornblende peridotite in the Hida Belt, Japan

Author: Keita Itano, Mami Takehara, Kenji Horie, Tsuyoshi Iizuka, Ikuya Nishio, Tomoaki Morishita

Issue&Volume: 2023-10-11

Abstract: Zircon geochronology has contributed to our understanding of the longevity of transcrustal magmatic systems; however, most studies focus on zircon records from felsic rocks due to the restricted occurrence of zircon in mafic-ultramafic rocks. We present UPb age, geochemical, and HfO isotope data for zircons from a hornblendite peridotite in the Hida Belt, Japan, that offers a unique opportunity to investigate the lifetime of a long-lived mafic plumbing system in an arc setting. We found two zircon UPb age clusters: an incompatible element-rich cluster at 196 Ma and an incompatible element-poor cluster at 186 Ma. Their homogeneous isotopic signatures (δ18O = 7.7‰ ± 0.8‰, εHf = 10.3‰ ± 1.7‰) indicate the same magma source despite the 10 m.y. age gap. These two clusters are explained by different zircon formation mechanisms that differ depending on whether or not zircon saturation requires differentiated melt with high SiO2. The enriched older zircons formed by local zircon saturation at the mafic melt-olivine interface, whereas the younger depleted zircons precipitated from the last drop of interstitial felsic melt co-existing with hornblendes. Our finding substantiates the longevity of mafic systems at lower crusts, which sustain transcrustal magma systems and crustal evolution.

DOI: 10.1130/G51560.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G51560.1/628564/A-long-lived-mafic-magma-reservoir-Zircon-evidenceredirectedFrom=fulltext