全球新生代苦橄岩时空分布特征及意义

Characteristics of the temporal-spatial distribution of global Cenozoic picrite and their significance

苦橄岩是一种高温下形成的超镁铁质熔岩,形成温度一般高出地幔部分熔融而成的玄武岩300~400℃,可以为判断热点提供依据。该文以GEOROC和PetDB两个地质数据库为基础,通过对其中新生代苦橄岩年龄及构造环境数据的统计分析,以期查明新生代苦橄岩的时空分布特征和厘定出可能的高温热点分布情况。研究表明,新生代有苦橄岩产出的火山活动自中新世开始变得活跃,在更新世和全新世达到顶峰。同时,苦橄岩产出环境多样且具有演变特征,中新世前以CFB和洋岛环境为主,中新世后转为岛弧和洋岛环境为主,更新世和全新世则主要为洋岛环境,总体上来看新生代苦橄岩主要产于大洋环境,并以洋岛环境为主。另外,根据苦橄岩的出露特征可得出现代高温热点可能分布在夏威夷群岛、科隆群岛(厄瓜多尔)、冰岛、加那利群岛、欧洲造山带德国境内的埃费尔山地区、红海洋脊、东非裂谷处、法属留尼汪岛、中国东南沿海广东省境内以及堪察加岛弧10个地区。

Picrite is a kind of ultral-mafic rock formed at temperatures about 300-400 ℃ higher than the melting temperature of the mantle-derived basalt,thus it can indicate the presence of hotspots.In this paper,based on two geological databases,GEOROC and PetDB,we aim to find out the temporal-spatial distribution characteristics of Cenozoic picrite and figure out the possible locations of modern hightemperature hotspots by analyzing the aging and tectonic environmental information in the two databases.The study shows that Cenozoic picrite volcanism became active in the Miocene and peaked in the Pleistocene and Holocene.Meanwhile,the tectonic environment of picrite is diverse and regularly changeable.Its tectonic characteristics changed from CFB and ocean island to volcanic arc and ocean island before and after the Miocene and then turned to ocean island in the Pleistocene and Holocene.In general,Cenozoic picrite is mainly produced in oceanic environment,especially ocean island.We conclude that,depending on the picrite exposure characteristics,modern hotspots are occurred in the following 10 locations:Hawaii islands,Colon islands(Ecuador),Iceland,Canary Islands,Effer mountain(Europe),Red Ocean Ridge,East African Rift,Reunion island,Guangdong Province(China)and Kamchatka arc.