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1.
东南沿海地区古近纪大陆岩石圈地幔特征及成因 总被引：3，自引：0，他引：3
东南沿海地区新生代玄武岩中的橄榄岩包体来自岩石圈地幔 ,上地幔橄榄岩包体的岩石学及地球化学特征都记录了地幔演化的历史。普宁橄榄岩包体斜方辉石含量与太古宙克拉通地幔类似 ,但在矿物学、REE、痕量元素和Sr Nd同位素上又与太古宙岩石圈地幔不同。橄榄岩包体的岩相学、矿物学、REE、痕量元素特征都提供了含H2 O富Si流体交代橄榄岩的证据 ,这种流体可能主要是洋壳物质局部熔融而成。流体交代使橄榄岩富Si,同时富Sr、Pb和强不相容元素等大洋岩石圈物质。这表明普宁大陆岩石圈地幔既保留太古宙岩石圈地幔的特征 ,又具有大洋俯冲地幔的特征 ,它是古老岩石圈地幔向大洋岩石圈地幔转换的一部分 ,这种转换可能是大洋岩石圈与大陆岩石圈地幔相互作用的结果。 相似文献
2.
上地幔熔体-岩石相互作用与大陆地幔演化 总被引：11，自引：2，他引：9
根据实验岩石学、幔源岩石的岩石地球化学资料以及微量元素地球化学理论模拟等,评述了上地幔熔体岩石相互作用研究领域的最新进展,指出熔体岩石相互作用不仅深刻地制约了岩石圈地幔的矿物学、地球化学和物理性质的变化以及地幔不均一性的形成及演化,而且也会最终控制各种构造环境下喷出岩浆的地球化学特征,以及深部岩浆的分离机制。 相似文献
3.
付建明 《矿物岩石地球化学通报》1995,(2)
海南岛蓬莱地区幔源包体的岩石地球化学特征付建明（宜昌地质矿产研究所，湖北宜昌４３３００３）关键词幔源包体，岩石地球化学特征，海南岛本区幔源包体的寄主岩石有橄榄玄武岩、碱性橄榄玄武岩和碧玄岩，它们的Ｋ－Ａｒ年龄为３．０４～５．４３Ｍａ，属晚第三纪火山喷... 相似文献
4.
吉林蛟河地幔橄榄岩捕虏体的Sr-Nd-Hf-Os同位素特征与岩石圈地幔时代 总被引：2，自引：2，他引：2
吉林省蛟河市境内大石河新生代玄武岩中含有丰富的地幔橄榄岩包体,详细的岩石学与矿物学研究显示,这些包体的主要岩石类型为尖晶石二辉橄榄岩-方辉橄榄岩,未发现石榴石橄榄岩。岩相学及地球化学资料显示它们都是经历过熔体抽取而形成的岩石圈地幔残留。矿物平衡温度计算发现,本区的这些地幔橄榄岩包体来自地下40～60km 深度,且下部以二辉橄榄岩为主,而上部以贫单斜辉石的二辉橄榄岩和方辉橄榄岩为主,显示明显的岩石圈地幔分层现象。Sr-Nd-Hf 同位素资料反映这些地幔包体均表现为亏损性质,而 Re-Os 同位素资料确定上述岩石圈地幔形成于中元古代,明显老于上覆地壳的新元古宙时代,反映壳幔年龄上的解耦。因此我们推测,该区曾经历过华北克拉通类似的早期岩石圈地幔的整体丢失事件,然后形成于其它地区的中元古宙岩石圈地幔在本区增生。 相似文献
5.
根据实验岩石学,幔源岩石的岩石地球化学资料以及微量元素地球化学理论模拟等,评述了上地幔熔体－岩石相互作用研究领域的最新进展,指出熔体－岩石相互作用不仅深刻地制约了岩石圈地幔的矿物学,地球化学和物理性质的变化以及地幔不均一性的形成及演化,而且也会最终控制各种构造环境下喷出岩浆的地球化学特征,以及深部岩浆的分离机制。 相似文献
6.
7.
长白山地区位于华北克拉通东北部,广泛出露富含地幔橄榄岩包体的新生代玄武岩,为研究岩石圈地幔的性质和演化提供了优越条件。本文对长白山地区天池和龙岗新生代火山岩群中尖晶石相橄榄岩包体进行了岩石学、全岩主微量元素、矿物主量元素、单斜辉石微量元素和Sr-Nd-Hf同位素分析。研究结果表明,尖晶石相橄榄岩包体由二辉橄榄岩和少量的方辉橄榄岩组成,Mg#值为87.4～91.2,表现出新生饱满的特征,平衡温度为900～1100℃。橄榄石的Mg#值(%Fo)为85.6～91.3。单斜辉石包括四种类型:(1)轻稀土元素严重亏损型;(2)轻稀土元素亏损型;(3)向右微倾型和(4)"勺型"。单斜辉石表现出Sr同位素(87Sr/86Sr=0.702749～0.707276)整体亏损,部分样品富集的特征,单斜辉石的Nd-Hf同位素呈现出亏损特征(143Nd/144Nd=0.512886～0.51333、εHf=+17.7～+49.8)。长白山地区二辉和方辉橄榄岩分别经历了小于10%和略大于10%的部分熔融作用,并受到富水硅酸盐熔体的地幔交代作用。太平洋板块向西俯冲作用使得软流圈上涌并携带大量壳源物质进入地幔深部,与岩石圈地幔发生橄榄岩-熔体反应,形成了长白山地区不均一的岩石圈地幔,以新增生饱满地幔为主,夹有少量古老难熔岩石圈地幔碎片。 相似文献
8.
东南沿海地区第四纪大陆岩石圈地幔的特征 总被引：5，自引：0，他引：5
东南沿海地区新生代玄武岩中的橄榄岩包体来自年轻的大陆岩石圈地幔 ,该岩石圈地幔在岩石学、矿物组成、痕量元素以及Sr Nd同位素组成等各方面具有很大差异。这些差异反映了它们来自不同的地幔过程。南海张开与地幔热柱有关 ,南海扩张后第四纪形成的火山岩携至地表的包体更多保留了地幔热柱的信息。橄榄岩包体的矿物成分与深海橄榄岩类似 ,相对贫Opx而富Ol;在痕量元素上 ,表现为强不相容元素的富集 ,其配分模式类似于其寄主岩 ;Nd同位素强烈亏损 ,显示出比MORB源区更亏损的特征。大陆岩石圈地幔经历了来自地幔深处的贫SiO2 熔体的进一步改造。 相似文献
9.
吉林省伊通地区橄榄岩包体的同位素特征与岩石圈地幔时代 总被引：6，自引：2，他引：4
吉林省伊通新生代火山群中大孤山所伴生的东小山火山含有丰富的地幔橄榄岩包体,详细的岩石学和矿物学工作显示,这些包体的主要岩石类型为尖晶石二辉橄榄岩,含有少量的方辉橄榄岩和异剥橄榄岩。包体的结构类型多样,包括粒状变晶结构、碎斑状结构、糜棱结构和筛状变晶结构。主量元素及矿物化学资料表明,这些地幔橄榄岩包体大都比较饱满,说明其所经历的部分熔融程度较低。微量元素显示,包体在形成以后经受过不同程度地幔交代作用的影响。矿物平衡温度计算结果表明包体的平衡温度为989～1142℃,来源深度约为40～70km。Sr-Nd-Hf同位素资料反映二辉橄榄岩包体具有亏损地幔的特征。Re-Os同位素资料显示上述岩石圈地幔的主体形成于显生宙期间,少量具有中元古代Re亏损年龄的样品所代表的古老地幔与本区上覆地壳成因无关,可能是软流圈中固有的较古老的大陆岩石圈地幔。 相似文献
10.
凉城、四子王旗、三义堂和大同的地幔包体的岩石学和矿物的主、微量元素成分显示华北克拉通中、西部北缘总体为过渡型岩石圈地幔,为原始地幔经过不同程度的熔体抽取和后期交代富集作用的残留.凉城岩石圈地幔经历的熔体抽取程度最低,后期交代富集作用比较强烈,这与其橄榄岩中尖晶石的Cr#较低,并且共存的单斜辉石的Mg#较低一致.三义堂岩石圈地幔经历的熔体抽取程度最高,后期交代富集作用最强烈,不同样品甚至同一样品中不同单斜辉石颗粒的La/Yb和LREE配分模式变化范围非常大,且矿物边部比核部更富集微量元素.大同、四子王旗岩石圈地幔经历的熔体抽取程度介于凉城和三义堂之间,但后期的交代富集作用明显不如凉城和三义堂强烈.研究区的岩石圈地幔主要受硅酸盐熔体交代作用的影响,只有三义堂岩石圈地幔还可能也受到了碳酸盐交代作用的影响. 相似文献
11.
Origin of the recrystallisation front in the Ronda peridotite by km-scale pervasive porous melt flow 总被引：5，自引：0，他引：5
It is well established that porous melt flow in the upper mantle may significantly affect partial mantle melt compositions.
Less well established are the length-scale of porous flow and whether porous melt flow can be a volumetrically important magmatic
process. The only source for observations concerning the length-scale and nature of pervasive porous melt flow are peridotite
massifs. Here we present such observations in the form of structural, and major and trace element data from peridotites of
the Ronda massif, southern Spain. Trace element concentrations were obtained with high analytical precision (ICP-MS) and include
trace elements rarely analysed in peridotites, such as Rb, Th, Nb and Ta. The western portion of the Ronda massif can be divided
into two structural facies. The first and oldest is composed of deformed, porphyroclastic spinel peridotites, the second of
virtually undeformed granular spinel peridotites. They are separated by a recrystallisation front across which grain growth
of all phases occurred. The granular domain can be further subdivided into three subfacies: coarse-granular, fine-granular,
and layered-granular peridotites. According to structural facies, km-scale spatial variations unrelated to Ca and Al abundances
have been recognised for mg-numbers [atomic Mg/(Mg±Fe)] and incompatible elements such as rare earth elements (REE), Th and
high-field-strength elements (HFSE; including Ti). Such variations are reminiscent of those commonly ascribed to mantle metasomatism,
but have never been documented on the km-scale. The origin of the recrystallisation front is related to km-scale pervasive
melt percolation. Feed-back processes between grain growth and melt fraction could have led to important accumulation of melt
at the recrystallisation front, accomplished mainly by melting/dissolution. Variation in melt fraction across the front explains
the spatial variation in the degree of recrystallisation, mg-numbers, REE fractionation, and HFSE abundances, and could account
for many of the classical differences between basalts from convergent and extensional tectonic settings. Whereas the coarse-granular
peridotites reflect a stage of steady-state pervasive porous melt flow, the fine- and layered-granular facies probably reflect
the terminate stages of porous melt flow. Processes associated with both domains are pyroxene-forming freezing reactions at
decreasing melt volumes, and progressive channelling of melt flow associated with olivine-producing reactions. Both processes
show complex overprinting relationships in both time and space.
Received: 10 January 1995/Accepted: 1 September 1995 相似文献
12.
Y.-G. Xu M. A. Menzies J.-L. Bodinier R. M. Bedini P. Vroon J.-C. C. Mercier 《Contributions to Mineralogy and Petrology》1998,132(1):65-84
Poikiloblastic harzburgite xenoliths (P-type) from Borée, France are characterised by large (>1 cm), essentially unstrained
olivines and high equilibrium temperatures (>1200 °C). Mineralogical data, trace element abundances and Sr-Nd-O isotopes of
the constituent minerals are consistent with formation as a result of melt percolation-reactions in a lherzolite precursor
during lithospheric erosion by an upwelling plume. This petrogenetic model contrasts with previous models involving isochemical
recrystallisation from a granular lherzolite precursor (G-type) or derivation as metacumulates from tholeiitic magmas. Numerical
simulation of percolation reactions at the lithosphere-plume boundary using the plate model of Vernières et al. (1997) indicates
that the different textured xenoliths may represent mantle from different levels in a percolation-reaction column. If correct
then the P-type harzburgites resulted from pyroxene-dissolving and olivine-producing reactions at increasing melt fraction
(>3%) at the lower part of column (base of the lithosphere), whereas the G-type lherzolites were located within the low-porosity
domain (<0.1%) above a permeability barrier, and are formed through a melt-rock reaction at decreasing melt mass. Given the
very low melt fraction, the REE fractionation in this zone is controlled by chromatographic effects coupled with source effects
of reaction. The variations in porosity, melt/rock ratio and melt-rock reaction mechanism are believed to be responsible for
the diversity of REE patterns and striking correlation between REE abundance and texture in Borée xenoliths.
Received: 15 June 1997 / Accepted: 7 January 1998 相似文献
13.
Petrology, Geochemistry and Tectonic Significance of the Metamorphic Peridotites from Longmuco–Shuanghu Ophiolitic Melange belt, Tibet 总被引：2，自引：0，他引：2
Taoxinghu metamorphic peridotite is a firstly reported mantle sequence of ophiolite since Longmuco–Shuanghu–Lancangjiang suture zone (LSLSZ) was proposed, and it is also an important discovered for ophiolite studying in central Qiangtang. Based on detailed analyses of whole–rock geochemistry of Taoxinghu metamorphic peridotites and contrast to metamorphic peridotites in typical ophiolites worldwide, the paper investigates their petrogenesis and geological implication. The petrologic results show that the protolith of Taoxinghu metamorphic perdotites have the mineral assemblage and texture characteristic of mantle peridotite. Most metamorphic peridotites hav near global abyssal peridotites major elements contents, while the few is similar to SSZ–type peridotites. They exhibit typically U–shaped REE patterns, characterized by slight enrichment of LREE and HREE relative to MREE and a low fractionated LREE to HREE segment. Trace elements contents are low and all samples are strong enrichment in Cs, U, Pb, weak enrichment in Ba and depletion in Th, but negative Nb anomalies are only observed in few samples. That suggests Taoxinghu metamorphic peridotites have depletion mantle and suprasubduction affinities. A two–stage evolution history is considered: Taoxinghu metamorphic peridotites originated as the residue from melting at a ridge with 7%–20% degree of fraction melting and were subsequently modified by interaction with mafic melt and aqueous fluid within mantle wedge on subducted zone. Combined with previous studies, we preliminarily propose Taoxinghu metamorphic peridotites may be the Products of initial rifting of palo–Tethys, forming at middle Ordivician–upper Cambrian, and they may be the direct evidences for spreading of palo–Tethys. 相似文献
14.
云南双沟变质橄榄岩中蛇纹石的稀土元素空间分布 总被引：2，自引：1，他引：2
本文探讨变质橄榄岩的ＬＲＥＥ富集型及Ｕ型分布的ＲＥＥ球粒陨石模型，是橄榄石固有的还是后期蚀变形成的。并寻求复原蚀变前橄榄石的ＲＥＥ丰度及型式。我们用蛇纹石颗粒代表蚀变后的橄榄石，用分选法和化学分层剥离法对样品进行予处理。用中子活化分析（ＮＡＡ）手段进行了测试。结果表明：分选法确定了ＬＲＥＥ的主要赋存载体是蛇纹石。分层剥离最后内核的ＲＥＥ丰度及模型，可近似地作为原来（未蚀变前）橄榄石的ＲＥＥ丰度及模型。 相似文献
15.
西藏西南部休古嘎布蛇绿岩的成因:岩石学和地球化学证据 总被引：2，自引：0，他引：2
休古嘎布蛇绿岩块位于雅鲁藏布缝合带(YZSZ)西段,主要由地幔橄榄岩和侵入其中的基性岩墙所组成。基性岩墙具有弧后盆地地球化学亲缘性,其LREE亏损,(La/Yb)N为0.39~0.55;具有明显的Nb、Ti负异常及Sr、Ba正异常。Sr、Nd同位素特征表明它们起源于亏损地幔,并且受到了板片析出流体的影响。4个基性岩墙的Sm-Nd同位素样品获得内部等时线年龄为126.2±9.1Ma(MSWD=0.44)。地幔橄榄岩具有汤勺形和U形两组REE分布型式,显示出不同程度部分熔融和地幔交代作用的特征,具有弧-盆体系地球化学亲缘性。第一组橄榄岩的LREE弱富集或近于平坦,尖晶石的Cr#值低而且变化不大,部分熔融程度较低(15%~20%),可能形成于弧后扩张盆地;第二组橄榄岩的LREE明显富集,尖晶石的Cr#值高而且变化较大(0.4~0.77),部分熔融程度较高(25%~30%),并经历了强烈的交代富集作用,可能与洋内岛弧有关。 相似文献
16.
大冶-武山矿化夕卡岩的稀土元素地球化学研究 总被引：15，自引：1，他引：15
用ICP-MS分析了25个含矿夕卡岩样品的REE含量,其中对8个样品的石榴子石等矿物中的熔融包裹体进行了均一温度测定,还对5个夕卡岩样品石榴子石中的熔融包裹体进行了电子探针分析.在这些样品的石榴子石、辉石或方解石中都观察到熔融包裹体.夕卡岩的球粒陨石标准化REE分布模式具有两个突出特点:其一是以富集轻稀土元素(LREE)右倾为特征;其二是多数以具有Eu正异常为特征.夕卡岩球粒陨石标准化REE分布模式有三种类型:第一类型显示斜率不大的右倾直线;第二类型具有以Ce为峰值的折线的特征,即REE线段向上凸,在Ce处有一极大值(个别无峰值,LREE曲线向上凸,呈穹隆状);第三类型为过渡型REE分布模式.在当今REE资料有限的情况下,利用稀土元素地球化学特点鉴别夕卡岩成因是困难的. 相似文献
17.
Many of the coarse-grained peridotite inclusions in basanitesfrom Nunivak Island, Alaska, contain amphibole and a smallerfraction also contain phlogopite and apatite. All of these peridotiteshave light REE/heavy REE abundance ratios greater than chondritesand many have abundances of K, Rb, Sr, Ba and light REE whichexceed estimates for primitive mantle. On the basis of mineraltextures and compositions we infer that the clinopyroxene, amphibole,phlogopite and apatite equilibrated with a metasomatic fluid.Isotopic (Sr and Nd) ratios and parent-daughter abundance datafor the coarse-grained peridotites constrain the age of themetasomatism to be less than 200 million years. Associated amphibole pyroxenite inclusions are not metasomatized;these inclusions probably formed as crystal segregates froman alkalic magma. Both pyroxenites and coarse-grained peridotitesare isotopically similar to basalts from Nunivak Island. Usingthese data, we propose a model in which the metasomatized peridotiteswere wallrocks located adjacent to the pyroxenites, and thatmetasomatism of these peridotites was caused by the infiltrationof a residual silicate melt or volatile-rich fluid derived fromthe parental magma of the pyroxenites; i.e. the metasomatismwas a consequence of basaltic magmatism. Furthermore, the parentalmagma of the pyroxenites was probably petrogenetically relatedto the Nunivak volcanism. REE modelling of fluids in equilibriumwith clinopyroxenes from the coarse-grained peridotites is consistentwith this model. 相似文献
18.
Clinopyroxene/melt and garnet/melt partition coefficients have been determined for Ti, Sr, Y, Zr, Nb, Hf, and rare earth
elements from 19 doped experiments on 1921 Kilauea basalt. The experiments were carried out from 2.0 to 3.0 GPa and 1310°
to 1470 °C. The purpose was to derive a set of partition coefficients for high-field-strength elements (HFSE) and rare earth
elements (REE) in a systematic, linked set of experiments at P and T conditions relevant to basalt petrogenesis. These data are used in melting models to understand the development of negative
HFSE anomalies observed in many abyssal peridotite clinopyroxenes. It is shown that melting can account for the observed trace
element patterns in some residual peridotites, but that other processes may also be needed to account for most residual mantle
compositions in mid-ocean ridge systems. It is also shown that REE are more strongly fractionated by garnet at these P-T conditions than previously thought.
Received: 1 July 1997 / Accepted: 11 May 1998 相似文献
19.
亏损上地幔中的富钾熔体和碳酸盐交代作用: 来自CCSD预先导孔橄榄岩的地球化学证据 总被引：1，自引：0，他引：1
中国大陆科学钻探工程预先导孔(CCSD-PP1) 打在苏鲁超高压变质带芝麻坊超镁铁岩体上,钻孔穿透超镁铁岩体115m.超镁铁岩体由二辉橄榄岩、方辉橄榄岩和少量单辉橄榄岩和纯橄岩组成,与上下围岩接触的橄榄岩被强烈蛇纹石化.多数橄榄岩含有石榴石或其假象,普遍含有金云母和菱镁矿,少量样品中有钛斜硅镁石.在化学成分上,橄榄岩的Mg#指数变化于90.392.6之间,MgO含量(36.61%49.15%,平均45.17%) 与Na2O (0.01%0.25%)、Al2O3 (0.07%3.71%,多数 < 2.0%,平均1.46%)和CaO (0.12%2.53%,一个高达3.30%,平均1.00%) 呈负相关关系.与主量易熔元素相对亏损的特点相反,橄榄岩中显示了稀土元素富集、分馏和配分曲线显示近于平行和相似的特点,(La/Lu) N比值为3.1833.05;此外,多数样品具有高Ba (最高比原始地幔高100多倍) 含量,在蛛网图上显示Rb、Nb、Ta、Zr、Hf和Sr的负异常,Ti/Eu比值均低于1300.岩相学特征和难熔主量元素与不相容元素之间的无相关性表明橄榄岩至少受到了形成金云母和菱镁矿的2次交代作用.富含金云母的橄榄岩(例如C25-143-61,C32-149-71) 具有富钾趋势,并且显示K2O与Rb、Ba和Th等大离子亲石元素的正相关关系,未见K2O和稀土元素、Sr和Ca之间的相关关系.这些特征表明橄榄岩被含水、硅铝质碱性熔体交代,之后又被高Ba低Rb和高场强元素的镁质(菱镁矿) 碳酸岩熔体交代,并且强烈地改变了Ba的丰度和显示了特定地幔碳酸盐的稀土元素配分型式.全岩具有不均一的高放射性Sr (87Sr/86Sr=0.70840.7201)和低放射性Nd (εNd (t) =-1.14-8.55) 组成,结合已有的氧同位素研究资料,表明预先导孔PP1中的橄榄岩所代表的地幔可能在早期就遭受了来自深部的介质的交代作用. 相似文献
20.
Martin Menzies 《Geochimica et cosmochimica acta》1976,40(6):645-656
Lherzolites from two Mediterranean peridotite masses have major and trace element data compatible with an origin as a fragment of relatively undepleted mantle. Field observations indicate a close association with in situ basaltic melt (gabbroic dikes and segregations) and a barren refractory residue (harzburgite) produced by the removal of the melt fraction.Two lherzolites Othris (ophiolite) and Lanzo (alpine1 periodotite) have approximately chondritic rare earth abundances with a slight depletion in light rare earths. The refractory material is moderately to heavily depleted in light REE dependent on the efficiency of removal of basaltic melt. Lherzolite xenoliths from the Massif Central probably contain an interstitial light REE enriched fraction as the recalculated lherzolite is depleted and not light REE enriched like the actual whole rock. These basaltic xenoliths are similar in major, trace and REE profile to the Lanzo and Othris mantle lherzolites, giving some indication of source homogeneity in the Mediterranean area. Partial fusion calculations on the Othris and Lanzo peridotites reveal that tholeiitic liquids could be generated by 10–30% partial melting. Such tholeiitic liquids separated from the Othris mantle section and probably formed early sea floor in a small ocean basin. Alkalic basalts are also associated with the Othris ophiolite as an early rifting sequence, and such liquids could have been generated from the source Iherzolite but difficulties would occur in removing such a liquid from the refractory residue. 相似文献