Large magnesium isotope fractionation in peridotite xenoliths from eastern North China craton: Product of melt-rock interaction
Large magnesium isotope fractionation in peridotite xenoliths from eastern North China craton: Product of melt-rock interaction
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华北克拉通东部橄榄岩捕虏体中大镁同位素分馏：熔岩相互作用的产物
DOI：
10.1016/j.gca.2013.04.011
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发表时间：
2013-08
影响因子：
5
通讯作者：
Yang, Wei
中科院分区：
文献类型：
--
作者：
Xiao, Yan;Teng, Fang-Zhen;Zhang, Hong-Fu;Yang, Wei
为了研究熔岩相互作用对地幔镁同位素分馏和地幔镁同位素不均一性的影响，报道了北中国克拉通东部25个橄榄岩包体的高精度镁同位素数据。这些包体的范围从二辉橄榄岩、富环氧氯丙烷的二辉橄榄岩到魏橄榄岩，并进行了不同的交代作用。二辉橄榄岩具有Ol，Fo含量在~90之间，镁同位素组成均一(δ26 mg=−0.26~−0.20)，与典型地幔相似。相反，富含环氧氯丙烷的二辉橄榄岩和魏橄榄岩具有较低的Ol和Fo含量(78-88)，并具有较大的镁同位素变化，δ为26 mg，−为0.39~+0.09。这些包体中矿物的δ26 mg值也是不同的，Ol的−为0.45~−0.03，OPx的−为0.26~−0.01，CPx的−为0.34~+0.22，Sp1的−为0.16~+0.25。二辉橄榄岩和大多数轻质辉石中共存的辉石和Ol之间的矿物间分馏(Δ26MgOpx-Ol=−0.04~+0.09‰；Δ26MgCpx-Ol=+0.02~+0.25‰)随温度变化，与平衡的矿物间同位素分馏一致。相反，在大多数富Cpx的二辉橄榄岩中，共存的辉石和Ol之间存在较大的不平衡镁同位素分馏(Δ26MgOpx-Ol=+0.16~+0.32‰；Δ26MgCpx-Ol=+0.04~+0.34‰)。这两种类型的同位素分馏也发生在Spl和Ol之间，Spl始终比Ol重(Δ26MgSpl-Ol=+0.15-+0.55‰)。总体而言，同位素平衡的轻辉橄榄岩可能是由于同位素轻熔体的地幔交代作用而产生的，而富CPx橄榄岩中较大的不平衡同位素分馏可能反映了熔体-橄榄岩相互作用过程中的动力学同位素分馏。这两种作用都导致了北中国克拉通东部岩石圈地幔中镁同位素组成的不均一性。
To investigate the effects of melt–rock interaction on Mg isotope fractionation and mantle Mg isotopic heterogeneity, we report high-precision Mg isotopic data of olivine (Ol), orthopyroxene (Opx), clinopyroxene (Cpx) and spinel (Spl) for 25 peridotite xenoliths from the eastern North China craton. These xenoliths range from lherzolites, Cpx-rich lherzolites to wehrlites, and are variably metasomatised. The lherzolites have Ol with Fo contents from 89 to 90 and have a homogeneous Mg isotopic composition (δ26Mg=−0.26 to −0.20), similar to the typical mantle value. By contrast, Cpx-rich lherzolites and wehrlites have lower Ol with Fo contents (78–88) and exhibit larger Mg isotopic variations, with δ26Mg ranging from −0.39 to +0.09. The δ26Mg values of minerals in these xenoliths are also variable and range from −0.45 to −0.03 in Ol, from −0.26 to −0.01 in Opx, from −0.34 to +0.22 in Cpx and from −0.16 to +0.25 in Spl. Inter-mineral fractionations between coexisting pyroxene and Ol in lherzolites and most isotopically light wehrlites (Δ26MgOpx–Ol=−0.04 to +0.09‰; Δ26MgCpx–Ol= +0.02 to +0.25‰) vary as a function of temperature and are consistent with equilibrium inter-mineral isotope fractionations. By contrast, large disequilibrium Mg isotope fractionation occurs between coexisting pyroxene and Ol in the majority of Cpx-rich lherzolites (Δ26MgOpx–Ol=+0.16 to +0.32‰; Δ26MgCpx–Ol=+0.04 to +0.34‰). Both types of isotope fractionations also occur between Spl and Ol, with Spl being consistently heavier than Ol (Δ26MgSpl–Ol=+0.15 to +0.55‰). Overall, the isotopically equilibrated but light wehrlites may result from mantle metasomatism by isotopically light melt, whereas large disequilibrium isotope fractionations in Cpx-rich peridotites likely reflect kinetic isotope fractionation during melt–peridotite interaction. Both processes result in the heterogeneous Mg isotopic composition of the lithospheric mantle beneath the eastern North China craton.
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DOI：
10.1016/0168-9622(86)90054-0
发表时间：
1986
期刊：
Chemical Geology: Isotope Geoscience Section
影响因子：
--
作者：
Z. Peng;R. Zartman;K. Futa;D. G. Chen
通讯作者：
Z. Peng;R. Zartman;K. Futa;D. G. Chen
影响因子：
5.3
作者：
P. V. Strandmann;K. Burton;R. James;P. Calsteren;S. Gíslason;B. Sigfússon
通讯作者：
P. V. Strandmann;K. Burton;R. James;P. Calsteren;S. Gíslason;B. Sigfússon
影响因子：
2.7
作者：
Yan Xiao;Hong‐fu Zhang
通讯作者：
Yan Xiao;Hong‐fu Zhang
影响因子：
5.3
作者：
H. Williams;A. Peslier;C. McCammon;A. Halliday;S. Levasseur;N. Teutsch;J. Burg
通讯作者：
H. Williams;A. Peslier;C. McCammon;A. Halliday;S. Levasseur;N. Teutsch;J. Burg
影响因子：
5.3
作者：
E. Tipper;A. Galy;J. Gaillardet;M. Bickle;H. Elderfield;E. A. Carder
通讯作者：
E. Tipper;A. Galy;J. Gaillardet;M. Bickle;H. Elderfield;E. A. Carder