The mean composition of ocean ridge basalts
The mean composition of ocean ridge basalts
复制标题
DOI：
10.1029/2012gc004334
复制
发表时间：
2013-03-01
影响因子：
3.5
通讯作者：
Schilling, Jean-Guy
中科院分区：
文献类型：
--
作者：
Gale, Allison;Dalton, Colleen A.;Schilling, Jean-Guy
大洋中脊玄武岩（MORB）的平均组成是使用全球数据集的主要元素，微量元素，和同位素汇编新的和以前公布的数据。一个全球目录的771脊段，包括其平均深度，长度和扩展速度，使计算的平均组成为每个部分。段平均值允许按段长度和扩展速率加权，并减少由不均匀采样引入的偏差。自举统计技术提供了严格的误差估计。根据这些数据的特点，我们建议对MORB的命名进行修订。“ALL MORB”是除弧后盆地外的地壳总成分，N-MORB是距热点沿着洋脊最可能遇到的玄武岩成分，D-MORB是亏损端元。所有MORB和N-MORB大大超过正常的脊玄武岩的早期估计更丰富。弧后扩张中心的平均成分要求更高程度的熔融和更高浓度的流体流动元素，反映了水对弧后岩石成因的影响。平均数据允许重新评估全球地球化学的几个问题。此处报告的K/U比（12，340 +/- 840）与之前的估计值雅阁，远低于阿雷瓦洛等人（2009）的估计值。ALL MORB和N-MORB的低Sm/Nd和Nd-143/Nd-144比值对地球具有非南极原始地幔的假设提供了限制。要么地球在Sm/Nd中是稀土的，假设是不正确的，要么MORB优先采样富集的储层，需要在地幔深部有一个大的贫化储层。
The mean composition of mid-ocean ridge basalts (MORB) is determined using a global data set of major elements, trace elements, and isotopes compiled from new and previously published data. A global catalog of 771 ridge segments, including their mean depth, length, and spreading rate enables calculation of average compositions for each segment. Segment averages allow weighting by segment length and spreading rate and reduce the bias introduced by uneven sampling. A bootstrapping statistical technique provides rigorous error estimates. Based on the characteristics of the data, we suggest a revised nomenclature for MORB. "ALL MORB" is the total composition of the crust apart from back-arc basins, N-MORB the most likely basalt composition encountered along the ridge >500 km fromhot spots, and D-MORB the depleted end-member. ALL MORB and N-MORB are substantially more enriched than early estimates of normal ridge basalts. The mean composition of back-arc spreading centers requires higher extents of melting and greater concentrations of fluid-mobile elements, reflecting the influence of water on back-arc petrogenesis. The average data permit a re-evaluation of several problems of global geochemistry. The K/U ratio reported here (12,340 +/- 840) is in accord with previous estimates, much lower than the estimate of Arevalo et al. (2009). The low Sm/Nd and Nd-143/Nd-144 ratio of ALL MORB and N-MORB provide constraints on the hypothesis that Earth has a non-chondritic primitive mantle. Either Earth is chondritic in Sm/Nd and the hypothesis is incorrect or MORB preferentially sample an enriched reservoir, requiring a large depleted reservoir in the deep mantle.