Basalts as probes of planetary interiors: Constraints on the chemistry and mineralogy of their source regions
Basalts as probes of planetary interiors: Constraints on the chemistry and mineralogy of their source regions
复制标题
玄武岩作为行星内部的探针：对其源区化学和矿物学的限制
DOI：
10.1016/0301-9268(80)90014-5
复制
发表时间：
1980
影响因子：
3.8
通讯作者：
J. Papike
中科院分区：
文献类型：
--
作者：
A. Bence;T. Grove;J. Papike
玄武岩岩浆是由行星内部部分熔融形成的，其成分反映了形成行星的物质的增生前历史、行星、随后的演化历史、源区的化学和矿物学，以及在源区和就位点运行的密集热力学参数。对来自地球、月球和长晶母体的玄武岩组的研究揭示了其来源区域内在的成分差异，而这些差异反过来又是地球及其形成和演化历史的特征。主要的星际差异是在铁、Mg （Mg+ fe2 +）、tio2、al2o3、na2o、Cr、Ni和挥发性元素丰度上观察到的。在地球上，最原始的海母玄武岩的Mg值为0.70 ~ 0.72，太古宙的橄榄岩科马长岩的Mg值高达0.9。欧几里亚钠的Mg值接近0.5（除了Binda）。这些差异反映了其来源中Mg （Mg+ fe2 +）的内在差异。行星玄武岩中tio2丰度的显著差异反映了源化学在行星间和行星内的变化。原始morb和原始大洋板内拉斑岩在相同Mg#下的tio2含量差异系数为2 - 3（分别为0.7-1.2和2 - 3 wt.%）。在mare套件中可以识别出三个主要的二氧化钛群；高tio2 (8-13 wt.%)，低tio2 （2 - 5 wt.%）和极低tio2 （< 1 wt.%）。重晶的tio2含量< 1 wt.%。与陆相玄武岩相比，海玄武岩和绿长岩的Na 2o含量明显减少。这是行星前吸积的结果，从形成月球和长晶石母体的物质中失去了挥发物。海玄武岩的al2o3含量始终低于陆相玄武岩。这可能是由于母源中al2o3的固有含量较低，或者它可能反映了al2o3在铝相中的保留。过渡金属在所有三套玄武岩中都有分选。对于陆生玄武岩，这可能反映了岩心分离；然而，对于月球和长晶母体的增生前分离的金属和硅酸盐是一个更合理的解释。在陆相玄武岩中观察到明显的铬异常，而在海玄武岩中没有。这似乎与各自地幔的o2差异有关。总的来说，这三种物体的稀土元素丰度是相当的。海玄武岩具有明显的负Eu异常，这种负Eu异常继承自海玄武岩源区，是月球历史早期（4.4-4.6 Ga）结晶岩浆洋斜长石移出的记录。地球上斜长石的早期分离似乎是一个相对不重要的过程。
Basalt magmas, derived by the partial melting of planetary interiors, have compositions that reflect the pre-accretionary history of the material from which the planet formed, the planets, subsequent evolutionary history, the chemistry and mineralogy of the source regions, and the intensive thermodynamic parameters operating at the source and emplacement sites. Studies of basalt suites from the Earth, its Moon, and the eucrite parent body reveal compositional differences intrinsic to their source regions which are, in turn, a characteristic of the planet and its formational and evolutionary history. Major interplanetary differences are observed in iron, Mg (Mg+ Fe 2+), TiO 2, Al 2 O 3, Na 2 O, Cr, Ni, and in volatile element abundances. The most primitive mare basalts have Mg# s∼ 0.6, on the Earth they are 0.70–0.72 for mid-ocean ridge basalts (MORBs) and up to 0.9 for Archean peridotitic komatiites. Eucrites have Mg# s approaching 0.5 (excepting Binda). These differences reflect inherent differences in Mg (Mg+ Fe 2+) of their sources. Striking differences in the TiO 2 abundances of the planetary basalts reflect both inter-and intra-planetary variations in source chemistry. Primitive MORBs and primitive oceanic intraplate tholeiites have a factor of 2–3 difference in TiO 2 at comparable Mg#(0.7–1.2 vs 2–3 wt.% respectively). Three major titania groups are recognized in the mare suite; high TiO 2 (8–13 wt.%), low TiO 2 (2–5 wt.%) and very low TiO 2 (< 1 wt.%). The eucrites have TiO 2 contents< 1 wt.%. The mare basalts and eucrites have pronounced Na 2 O depletion relative to all terrestrial basalts. This is a consequence of the preplanetary accretion loss of volatiles from the material that formed the Moon and the eucrite parent bodies. Mare basalts have consistently lower Al 2 O 3 contents than the terrestrial basalts. This may be due either to an inherently lower content of Al 2 O 3 in the mare sources or it may reflect Al 2 O 3 retention in an aluminous phase. The transition metals are fractionated in all three basalt suites. For terrestrial basalts this may reflect core-separation; however, in the case of the Moon and eucrite parent bodies pre-accretionary separation of metal and silicates is a more reasonable explanation. A pronounced Cr anomaly is observed in terrestrial MORBs but not in the mare basalts. This appears to be related to f O 2 differences in the respective mantles. Overall rare earth element abundances are comparable between all three objects. Mare basalts have a pronounced negative Eu anomaly which is inherited from their source region and is record of plagioclase removal from crystallizing magma ocean early in lunar history (4.4–4.6 Ga). Early separation of plagioclase on the Earth appears to have been a relatively unimportant process.