摘要:在岩浆结晶演化过程中，橄榄石是最早结晶的矿物之一，其化学成分不仅受到母岩浆成分的控制，而且还受到岩浆的结晶分异、部分熔融程度、压力、岩浆混合作用以及橄榄石与残余岩浆相互作用等因素的影响。学术界基本的认识是，橄榄石的成分主要与源区、分离结晶作用以及岩浆演化程度有关，是鉴别玄武岩是否为原始岩浆的重要证据，根据橄榄石的Fo值可以恢复岩浆是富镁还是富铁的。之前的学术界很少认为橄榄石与其形成的构造环境有关。本文在对全球大洋中脊玄武岩（MORB）、洋岛玄武岩（OIB）、岛弧玄武岩（IAB）中橄榄石主量元素特征进行了研究和对比后发现，橄榄石也有判断构造环境的功能，尤其OIB 橄榄石在许多元素含量上与MORB 和IAB 的橄榄石不同，可以通过Ni、P、Mg、Fe、K 和Mn等元素之间的关系进行较好的区分。目前的情况是，OIB 与IAB 中的橄榄石在某些情况下也能够区分开，但MORB 与IAB 中的橄榄石很难区分，这是需要进一步研究的。全球全体数据研究表明，OIB 的橄榄石富Ni是一个很重要的现象，本文认为，MORB 和IAB 来源于亏损的上地幔，故其橄榄石的Fo值高；OIB来源于富集的下地幔，可能Fe-Ni地核对OIB橄榄石化学成分有比较明显的影响，故导致OIB的橄榄石贫Fo和富Ni。?
关键词: 洋中脊玄武岩/
洋岛玄武岩/
岛弧玄武岩/
橄榄石/
化学成分/
判别图
Abstract:Olivine is one of the earliest crystallized minerals in the process of magma crystallization evolution. Its chemical composition is not only controlled by the parent magma composition, but also influenced by the crystallization differentiation of magma, part melting degree, temperature, pressure, magmatic mixing, the reaction between olivine and residual magma. The basic understanding is that the main composition of olivine is mainly related to the source area, fractional crystallization and magma evolution degree, which is important evidence to figure out whether the basalt is from original magma or not. According to the value of Fo we can rebuild the magma is rich in Mg or Fe. Few previous researchers believed that olivine was related to the tectonic environment. Based on the study of main elements of olivine in global mid-ocean ridge basalt（MORB）, ocean island basalt（OIB）and island arc basalt（IAB）, we find that olivine can be used to discriminate the tectonic background, especially the OIB has much difference with MORB and IAB in many elements. MORB and OIB can be distinguished by Ni, P, Fo, K, Mn, and OIB and IAB also can be distinguished in some cases, however, it is difficult to distinguish the olivine in MORB and IAB, which needs further study. Global data research shows that Ni-rich of olivine in OIB is a very important phenomenon, this paper believes that MORB and IAB derive from the depleted upper mantle, so value of Fo is high; OIB derives from the enriched lower mantle, and Fe-Ni core may have significant effect on its chemistry composition, which leads to olivine is poor in Fo and rich in Ni in OIB.?
Key words:Mid-ocean ridge basalt/
Ocean island casalt/
Island arc basalt/
Olivine, Main elements/
Chemistry composition/
Discrimination diagrams
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