The importance of crystal chemistry on REE partitioning between mantle minerals (garnet, clinopyroxene, orthopyroxene, and olivine) and basaltic melts
The importance of crystal chemistry on REE partitioning between mantle minerals (garnet, clinopyroxene, orthopyroxene, and olivine) and basaltic melts
复制标题
DOI：
10.1016/j.chemgeo.2013.08.045
复制
发表时间：
2013-11
期刊：
影响因子：
3.9
通讯作者：
Chenguang Sun;Yan Liang
中科院分区：
文献类型：
--
作者：
Chenguang Sun;Yan Liang
稀土元素在地幔矿物和玄武岩熔体之间的分配是理解晶体-熔体分馏过程的基础，可以用晶格应变模型定量描述。我们使用非线性回归方法分析了已发表的石榴子石和玄武质熔体之间的REE和Y分配数据以及橄榄石和玄武质熔体之间的REE、Y和Sc分配数据，并将晶格应变模型中的关键分配参数（D 0、r 0和E）参数化为温度、压力以及矿物和熔体成分的函数。结果表明，REE和Y在石榴子石和玄武质熔体中的分配系数与温度和压力呈负相关，REE分配系数与石榴子石中Ca含量（XCa）的相关性为D 0与XCa的负相关和r 0与XCa的正相关所卷积。REE、Y和Sc在橄榄石和玄武岩熔体间的分配系数与橄榄石中Al含量呈正相关，与橄榄石中镁橄榄石含量和压力呈负相关。为了测试模型开发中使用的假设和简化的有效性，我们结合了石榴石和橄榄石模型与最近的单斜辉石和玄武岩熔体之间的稀土元素分配模型，以获得两个矿物-矿物分配模型。我们发现，模型推导的石榴石-单斜辉石和橄榄石-单斜辉石的稀土元素分配系数是一致的，从平衡良好的榴辉岩和橄榄岩捕虏体在亚固相线条件下的测量数据。这证明了我们的参数化晶格应变模型的内部一致性稀土分配石榴石，橄榄石，单斜辉石和斜方辉石。总的来说，石榴石，橄榄石，单斜辉石和斜方辉石的分区模型都表明晶体化学，温度和压力在确定地幔矿物和玄武岩熔体之间的稀土元素分配的重要性，熔体成分只有次要或间接的影响。
Partitioning of rare earth elements (REEs) between mantle minerals and basaltic melts is fundamental to understanding crystal-melt fractionation processes and can be quantitatively described by the lattice strain model. We analyzed published REE and Y partitioning data between garnet and basaltic melt and REE, Y, and Sc partitioning data between olivine and basaltic melt using the nonlinear regression method, and parameterized key partitioning parameters in the lattice strain model (D0,r0andE) as functions of temperature, pressure, and mineral and melt compositions. We show that REE and Y partition coefficients between garnet and basaltic melt are inversely correlated with temperature and pressure, and that the correlation between REE partition coefficients and Ca content in garnet (XCa) is convoluted by the inverse relationship betweenD0and XCaand the positive correlation betweenr0and XCa. REE, Y, and Sc partition coefficients between olivine and basaltic melt are positively correlated with Al content in olivine and inversely correlated with forsterite content in olivine and pressure. To test the validity of the assumptions and simplifications used in the model development, we combined the garnet and olivine models with a recent model for REE partitioning between clinopyroxene and basaltic melt to obtain two mineral–mineral partitioning models. We found that the model-derived garnet-clinopyroxene and olivine-clinopyroxene REE partition coefficients are consistent with the measured data from well-equilibrated eclogite and peridotite xenoliths at subsolidus conditions. This demonstrates the internal consistency of our parameterized lattice strain models for REE partitioning in garnet, olivine, clinopyroxene and orthopyroxene. Taken collectively, the partitioning models for garnet, olivine, clinopyroxene and orthopyroxene all suggest the importance of crystal chemistry, temperature and pressure in determining REE partitioning between mantle minerals and basaltic melts, and that melt composition has only a secondary or indirect effect.