中国东部几个地区新生代玄武岩中单斜辉石—熔体平衡温压—兼论幔源包体的成因

以中国东部宽甸、汉诺坝和明溪含有幔源包体的新生代玄武岩中的单斜辉石斑（巨）晶为研究对象,采用最新的单斜辉石－熔体平衡温压计对单斜辉石斑（巨）晶－熔体进行了平衡温压计算。结果表明,碱性玄武岩中的单斜辉石斑晶结晶温度和压力高于共生的亚碱性玄武岩中的单斜辉石斑晶,单斜辉石巨晶的结晶温度和压力高于单斜辉石斑晶。这说明碱性玄武岩的形成深度大于亚碱性玄武岩,单斜辉石巨晶是更高压力下的结晶产物,单斜辉石斑晶在岩浆上升的不同深度均有晶出。回归分析表明,尽管携带幔源包体的玄武岩浆上升速度较快,但并不是绝热上升。单斜辉石斑（巨）晶的结晶温压条件与同一地点幔源包体平衡温压条件的对比表明,单斜辉石巨晶和碱性玄武岩中的部分单斜辉石斑（巨）晶的结晶温压大于幔源包体的平衡温压,表明了包体寄主岩浆的来源深度大于包体的深度。因此,幔源包体是寄主岩浆上升途中捕虏的上地幔碎块,而非寄主岩浆形成源区的残留体。     

大陆亚碱性火山岩的成因多样性：以敦化—密山和东宁火山岩带为例

对东北牡丹江海浪、鸡西鸡林、东宁老黑山三处亚碱性玄武岩类进行了柏A卜”Ar定年和元素与Sr-Nd-Pb同位素组成研究,结果显示,始新世海浪（玄武）安山岩属钙碱性系列,相对富硅碱,贫铁钙,高度富集Rb、Ba、Sr,亏损Th、U、Nb、Ta,富集LREE及极低的HREE含量,与五大连池钾质火山岩相近的同位素组成（^206Pb／^204Pb=16．56～16．66,^207Pb／^204Pb=15．44—15．47,^208Pb／^204Pb=36．80—36．95;ISr=0．704882～0．705564;εNd=-4．05～2．29）,表明来源于较厚的、受交代作用影响的含石榴石富集（LoMu）岩石圈地幔;中中新世鸡林拉斑玄武岩分布极为局限,辉石斑晶发育骸晶结构,富铁、钙、钛,不亏损Nb、Ta,富集Ba、Sr,REE相对平坦,HREE高于OIB,Sr、Nd同位素组成相似于Samoa岛玄武岩,显示源区除软流圈成分外,还有EMII富集组分的加入;晚中新世老黑山拉斑玄武岩,低碱低钾,LREE轻度富集,Nb、Ta不明显亏损,同位素比值与镜泊湖一带中新世碱性玄武岩范围一致,主要来源于软流圈并与富集岩石圈（EMI）发生过相互作用。地幔源区经历了古近纪富集地幔源到中新世软流圈组分增多的演化。东北新生代拉斑玄武岩不同的地球化学特征为认识大陆拉斑玄武岩成因的多样性提供了有益启示。     

中国东部新生代玄武岩中巨晶矿物的地球化学

本文对安徽女山、河北汉诺坝和广东普宁碱性玄武岩中的单斜辉石和角闪石巨晶进行了主要元素、稀土元素、微量元天和Ｓｒ＿Ｎｄ同位素的综合分析。数据显示产出于３个研究区的单斜辉石巨晶有３类：Ａｌ普通辉石、透辉石和Ｆｅ＿Ｎａ透辉石。普宁地区的角闪石巨晶乃世界上罕见的绿钙闪石巨晶。女山和普宁的单斜辉石和角闪石巨晶是碱性玄武岩浆在幔源高压下的结晶产物；汉诺坝的单斜辉石巨晶既可以是碱性玄武岩浆又可以是拉斑玄武岩浆的高压结晶体。所有巨晶相对于寄主岩者属于偶然捕掳晶。巨晶的形成符合“流动结晶模式”。它们与共存的橄榄岩色体无成因     

南海新生代玄武岩中单斜辉石地球化学特征 及其地质意义

南海新生代玄武岩中发育有大量的单斜辉石斑晶,与橄榄石、角闪石等斑晶共存,多数被熔蚀,呈浑圆状,部分发育有很窄的反应边。研究表明单斜辉石具有巨晶的特征,是在高压下在与寄主岩同源的岩浆中形成,没有经历长时间的沉淀生长而直接向上运移被带到地表,因而具有巨晶的主量及微量元素的特征却不具有巨晶的形态。单斜辉石稀土元素含量不高,HREE及LREE亏损,而MREE富集;大离子亲石元素Rb、Ba、Sr均出现明显的亏损,高场强元素Nb、Zr出现亏损而Hf略富集。Nb、Ta与Zr、Hf分馏明显。Th较为富集,而Pb强烈亏损,U的变化范围较大。研究发现南海新生代玄武岩中的单斜辉石的来源较为简单,为地幔柱的直接产物,并没有受到洋中脊—地幔柱相互作用的影响,由于岩浆上升速度较快压力迅速下降,橄榄石大量晶出,引起了岩浆成分的变化,致使单斜辉石与寄主岩成分和结构上没有达到平衡。     

吉林平岗-渭津中性-中基性火山岩特征及成因

平岗-渭津中性-中基性火山岩的岩石化学特征显示:岩石类型主要有钾玄岩、玄武安山岩、安山岩、歪长粗面岩,岩浆系列以高K钙碱性系列为主,伴有钾玄岩系列和拉斑玄武岩系列;轻稀土富集,Eu异常不明显;Sr、K、Rb、Ba、Th等强不相容元素富集、高场强元素Nb相对亏损,反映出火山岩具火山弧与板内玄武岩构造背景的双重性.钾玄岩的Mg值及Ni含量表明钾玄岩属进化了的基性岩浆.根据Nd、Sr同位素比值及英安岩中辉石巨晶的结晶深度、松辽盆地东侧的地壳厚度等资料,认为钾玄岩浆来源于幔源基性岩浆.通过对岩浆密度及结晶压力、温度的估算认为多斑钾玄岩的形成与岩浆密度、斜长石密度及斜长石的结晶压力有关.     

延边地区中生代火山岩的岩浆源区:来自Sr-Nd同位素和深源捕虏体(晶)的证据

延边地区中侏罗世和早白垩世火山岩中包含有较多的辉石岩捕虏体和角闪石捕虏晶,前者为普通辉石变种,其化学成分类似于中国东部新生代玄武岩中单斜辉石巨晶的成分,具有岩浆堆积成因特征;后者为韭闪石和镁质绿钠闪石变种,其成分类似于中生代晚期玄武岩中角闪二辉石岩包体里的角闪石和新生代玄武岩中的角闪石巨晶.矿物温压计算结果显示,它们形成深度介于25～37km.延边地区中生代火山岩的(87Sr/86Sr)i值介于0.704 3～0.705 0,εNd(t)值介于2.33～4.71,表明岩浆源区应是一套具有亏损性质的新增生的地幔物质.综合上述结果,可以判定延边地区中生代火山岩的原始岩浆应来源于新增生的壳幔过渡带物质的部分熔融,地壳增生事件的时间为新元古代.     

太行山地区中、新生代玄武质岩浆的源区特征与时空演化

本文总结了太行山地区中生代辉长岩和新生代玄武岩的元素和同位素组成，其组成显示它们的地幔源区存在着明显的差别。新生代玄武岩以碱性玄武岩为主，含有少量橄榄拉斑玄武岩，它们来自软流圈的部分熔融，并伴有少量古老岩石圈地幔组分的加入。相比之下，中生代辉长岩具有明显不同的地球化学特征：SiO2含量高，LREE和LILE（Ba，Th，U）富集以及HFSE（Nb，Ta，Zr和Ti）亏损，Sr-Nd同位素富集（大多数^87Sr／^86Sri〉0．705，^143Nd／^144Nd；〈0．512）、Pb同位素亏损（^206Ph／^204Pbi〈17．5，^207Ph／^204Pbi〈15．5，^208Pb／^204Pbi〈38．0）。这些特征表明中生代辉长岩来源于经过富硅熔体强烈改造的古老岩石圈地幔，这种富集改造过程很可能与华北克拉通内部元古代的俯冲／碰撞事件有关。古老且同位素富集的岩石圈地幔残存至新生代，并被新生代玄武岩携带的地幔橄榄岩捕虏体所记录。     

汉诺坝捕虏体辉石岩和麻粒岩的成因探讨

汉诺坝新生代玄武岩中含有丰富的地幔和地壳岩石捕虏体,其中捕虏体辉石岩和庥粒岩由于外观上具有一定的相似性,两者容易混淆,导致研究上的误区.本文以辉石岩和麻粒岩捕虏体作为研究对象,通过岩相学观察结合矿物主量元素分析、单斜辉石微量元素和Sr-Nd同位素分析,对两种捕虏体进行深入的研究和对比以探讨其成因意义.结果表明,上述各方面二者都存在明显的差别,捕虏体麻粒岩具有层状堆晶构造,两种辉石矿物(次透辉石和古铜辉石)相对贫MgO富FeO,单斜辉石的REE相对富集,以高87Sr/86 Sr低143Nd/144Nd为特征;而捕虏体辉石岩一般呈块状构造,两种辉石矿物(透辉石和古铜辉石-顽火辉石)相对富MgO贫FeO,单斜辉石REE总量极低呈亏损模式,同位素组成上介于捕虏体橄榄岩和麻粒岩之间.捕虏体麻粒岩特征表明它是幔源岩浆底侵作用形成,岩浆受到了下地壳的混染;而捕虏体辉石岩明显不同于橄榄岩和麻粒岩的成因,来自于富集地幔.     

福建龙海天马山-牛头山玄武岩中捕虏体和巨晶特征的研究

本文研究了天马山-牛头山新生代玄武岩中二辉橄榄岩和橄辉斜长岩捕虏体的岩石学、矿物学和地球化学等特征并论及碱性玄武岩中单斜辉石和歪长石巨晶。尖晶石二辉橄榄岩存在于碱性玄武岩和橄榄拉斑玄武岩中,由尖晶石、橄榄石、斜方辉石、铬透辉石等组成,与模拟地幔岩相比,具低的MgO含量和不相容元素Ti丰度而富集Co、Ni相容元素。尖晶石二辉橄榄岩具低的稀土总量和平缓的球粒陨石标准化稀土元素分配模式,形成于温度约1000℃、深度为50—80公里的上地幔。橄辉斜长岩具正堆积结构,Al_2O_3、CaO、∑REE和La/Yb明显高于二辉橄榄岩。但MgO含量远低于后者,反映两者成因的不一致性。普通辉石巨晶以富铝为特征,歪长石以富钙为特征。     

滇东南马关巨晶单斜辉石原位Sr同位素特征及其含水性

对滇东南马关火山爆砾岩筒以及玄武岩中的单斜辉石巨晶进行了主量元素、微量元素、原位Sr同位素以及含水性研究,结果显示,单斜辉石巨晶均为铝质普通辉石,Mg#与Al、Fe、Ti呈负相关,与Ca呈正相关;稀土元素总量不高,HREE及LREE亏损,而MREE相对富集,大离子亲石元素均出现明显亏损,高场强元素Nb、Zr出现亏损而Hf略富集,Nb、Ta与Zr、Hf分馏明显,Rb、Ba的变化范围较大。原位Sr同位素87Sr/86Sr值为0. 703 92～0. 705 06,巨晶单斜辉石来源于上地幔,形成于同一母岩浆,与寄主玄武岩同源,为源岩浆在高压下的结晶产物。运用显微红外-傅里叶变换红外光谱仪(Micro-FTIR)分析测试了单斜辉石巨晶的水含量,结果显示OH吸收峰位于3 700～2 800cm-1,含水量赋值范围为318×10-6～693×10-6,水含量稍富于女山及汉诺坝地区的单斜辉石巨晶,也高于马关地区幔源橄榄岩包体中的单斜辉石结构水含量,暗示该区上地幔岩石圈具高含水性,这同时证实了俯冲洋壳在研究区的活动。新近纪到达地幔过渡带的西太平洋洋壳俯冲发生转向东撤,此时新特提斯洋洋壳正在NE向俯冲,是马关地区深部地幔富水的主因,到达软流圈(或地幔过渡带)的新特提斯洋俯冲洋壳导致该区地幔熔融,岩浆随之而生。     

山东胶州大西庄辉石巨晶Sr-Nd同位素组成及其源区性质

胶州大西庄玄武岩（73 Ma）中的辉石巨晶与寄主玄武岩具有几乎完全相同的同位素组成,其⁸⁷Sr/⁸⁶Sr（t）和ε_Nd（t）分别为0.703 3～0.704 1、+4.5～+6.5和0.703 5～0.703 8、+7.1～+7.6,暗示辉石巨晶和寄主岩具有相同的地幔源区,即辉石巨晶是玄武岩浆在高压下结晶的产物.亏损的同位素特征表明：在白垩世末期（～73 Ma）,胶东地区的岩石圈地幔已经由富集转变为亏损,表现出类似于中国东部新生代地幔的同位素特征,即表明当时岩石圈减薄（或置换）已经完成.     

Origin of clinopyroxene megacrysts in volcanic rocks from the North China Craton: a comparison study with megacrysts worldwide

ABSTRACT

Clinopyroxene megacrysts in volcanic rocks can provide substantial information on the evolution of the magmatic system at depth. Although considerable attention has been paid to these crystals, their origin is not yet completely resolved. The clinopyroxene megacrysts worldwide can be divided into two major types in general: the green Cr-diopside type and the black Al-augite type. There is a consensus view that the Cr-diopside megacrysts are mantle xenocrysts, whereas two contrasting opinions exist regarding the origin of the black Al-augite megacrysts. One favours a cognate origin, viewing them as crystallization products of the host magmas under high-pressure; while the other argues that they are xenocrysts crystallized from previous alkali basalts or fragments of mantle peridotites, pyroxenites or pegmatite veins. A review study on the clinopyroxene megacrysts in Meso-Cenozoic volcanic rocks from the North China Craton (NCC) and their comparison with those worldwide provides new constraints on their origin, namely, the Cr-diopside megacrysts, as previously thought, are all xenocrysts, representing disaggregated clinopyroxene crystals from clinopyroxene-rich mantle rocks. Contrary to the formerly proposed cognate origin, the Al-augite megacrysts are also xenocrysts, having no direct genetic link to their host rocks. They crystallized from melts that have formed earlier than the host magmas, and probably accumulated in a magma chamber or occurred as sheets or veins filling a fracture network surrounding a magma chamber in the upper mantle. During the subsequent eruption of the host lavas, these previously formed crystals were incorporated into the magma and were brought up to the surface.     

中国东部碱性玄武质岩石中的辉石和角闪石巨晶

在中国东部,北起黑龙江、南到海南岛,广泛地分布着新生代碱性玄武质岩石,例如碱性橄榄玄武岩、碧玄岩、霞石玄武岩等。它们含有丰富的超镁铁岩包体和各种巨晶。已发现的有辉石、角闪石、石榴石、歪长石、钛铁矿和云母等巨晶。Harte(1978)把巨晶定义为大的单矿物单个晶体,它比超镁铁岩团块中的矿物粗得多(2—20cm)。然而有的地质学家把巨晶的粒度下限定在1cm(Eggler 等,1979)。笔者遵循这一定义和采纳后一界线,在此基础上着重对中国东部部分地区的辉石和角闪石巨晶进行研究,研究情况见表1。     

汉诺坝幔源单斜辉石巨晶氢同位素组成的离子探针分析:微尺度不均一性

运用离子探针技术测定了河北汉诺坝新生代玄武岩中3个单斜辉石巨晶的氢同位素组成,结果显示同一颗粒内部表现出微尺度的不均一性,2mm范围内δD的变化达到60‰。δD和氢含量之间不存在同步的变化,巨晶内部的化学成分均一,因此我们认为巨晶的氢同位素不均一性继承自母岩浆。母岩浆的氢同位素变化可能是去气过程中气相与熔体之间的分馏引起的。单斜辉石巨晶形成后很短的时间内即被寄主岩浆带至地表并经历了快速淬火。     

雷琼地区晚新生代玄武岩地球化学：EM2成分来源及大陆岩石圈地幔的贡献

对雷琼地区21个晚新生代玄武岩样品的主量、微量元素和Sr、Nd、Pb同位素分别用湿化学法、ICP-MS和MC-ICPMS进行了测定.这些玄武岩主要为石英拉斑玄武岩,其次为橄榄拉斑玄武岩和碱性玄武岩.大多数样品的微量元素和同位素成分与洋岛玄武岩(OIBs)相似,而且随着SiO_2不饱和度增加,不相容元素含量也增加.除R4-1可能受到地壳混染外,其他样品相对均一的Nd同位素(ε_(Nd)=2.5-6.0)以及变化明显但范围有限的Sr同位素(0.703106～0.704481),可能继承了地幔源区的特征.~(87)Sr/~(86)Sr与~(206)Pb/~(204)Pb的正相关和~(143)Nd/~(144)Nd与~(206)Pb/~(204)Pb的负相关特征暗示DM(软流圈地幔)与EM2(岩石圈地幔)的混合.地幔捕虏体的同位素特征暗示EM2成分不可能存在于尖晶石橄榄岩地幔,而La/Yb和Sm/Yb系统表明岩浆由石榴石橄榄岩部分熔融产生,这意味着EM2成分可能存在于石榴石橄榄岩地幔.雷琼地区玄武岩的地球化学变化可以用软流圈地幔为主的熔体加入不同比例石榴石橄榄岩地幔不同程度熔融产生的熔体来解释:碱性玄武岩和橄榄拉斑玄武岩是软流圈熔体与石榴石橄榄岩地幔较低程度(7%～9%)熔融体混合,而石英拉斑玄武岩是软流圈熔体与石榴石橄榄岩地幔较高程度(10%～20%)熔融体的混合.     

河北汉诺坝玄武岩中深源包体和巨晶分布的动力学机理

汉诺坝碱性玄武岩是深源包体和巨晶的主要寄主岩,同时,也有不含包体的碱性玄武岩和含包体的拉斑玄武岩。本文基于理论计算,探讨了包体和巨晶分布的动力学机理。     

The Skien lavas, Oslo Rift: petrological disequilibrium and geochemical evolution

The Skien lavas, which form the earliest phase of basaltic magmatism within the Permo-Carboniferous Oslo Rift, contain multiple generations of clinopyroxene which exhibit strong petrological and geochemical disequilibrium. Three principal core compositions have been identified: (1) low-jadeite, high-Mg, Cr-diopside cores (CrMgDi) with strongly depleted trace-element signatures, which are believed to be xenocrystic in origin; (2) Mg-rich, Cr-poor diopside cores (MgDi) with moderately depleted trace-element signatures which probably represent early cognate growth; and (3) more dominant, low-Mg, phenocrystic diopside cores (PhenDi). Several samples contain CrMgDi or MgDi cores which have been subjected to resorption and partial re-equilibration with their host melts, indicative of extensive disequilibrium and magma mixing. These three core types are overgrown by trace-element-enriched Ti-augite, which also forms megacrysts and late-stage lava groundmass. Calculated Ti-augite/melt partition coefficients show clinopyroxene compatibility of the M-HREE, Zr, Hf and Y. The LILE, Sr, and Nb remain incompatible. )Sr₃₀₀ and )Nd₃₀₀ of Ti-augite overgrowths, phenocrystic diopside, and MgDi diopside cores show that intrasample isotopic disequilibrium existed when the host basalts were erupted. All epsilon values lie within the range of data previously published for the Skien lavas. Detailed examination of the chemical, isotopic and textural disequilibrium features seen in these lavas has enabled us to place constraints upon the magmatic evolution of this basalt suite, ranging from xenocryst incorporation to cognate multistage pyroxene growth, as well as identifying clear evidence of magma mixing and possible crustal contamination.     

Geochemical and geochronological study of the Sanshui basin bimodal volcanic rock suite,China: Implications for basin dynamics in southeastern China

Sanshui basin is one of the typical Mesozoic–Cenozoic intra-continental rift basins with voluminous Cenozoic volcanic rocks in southeastern China. Thirteen cycles of volcanic eruptions and two dominant types of volcanic rocks, basalt and trachyte–rhyolite, have been identified within the basin. Both basalt and trachyte–rhyolite members of this bimodal suit have high values of εNd (+2.3 to +6.2) and different Sr isotopic compositions (initial ⁸⁷Sr/⁸⁶Sr ratios are 0.70461–0.70625 and 0.70688–0.71266 for basalts and trachyte–rhyolite, respectively), reflecting distinct magma evolution processes or different magma sources. The results presented in this study indicate that both of the trachyte–rhyolite and basaltic magmas were derived from similar independent primitive mantle, but experienced different evolution processes. The trachyte-rhyolitic magma experienced significant clinopyroxene and plagioclase fractionational crystallization from deeper magma chamber with significant crustal contamination, while the basaltic magmas experienced significant olivine and clinopyroxene fractionational crystallization in shallower magma chamber with minor crustal contamination. New zircon U–Pb dating confirms an initial volcanic eruption at 60 Ma and the last activity at 43 Ma. Geologic, geochemical, and geochronological data suggest that the inception of the Sanshui basin was resulted from upwelling of a mantle plume. The Sanshui basin widened due to subsequent east–west extension and the subsequent volcanism constantly occurred in the center of the basin. Evidence also supports a temporal and spatial association with other rift basins in southeastern China. The upwelling mantle plume became more active during late Cenozoic time and most likely triggered opening of other basins, including the young South China Sea basin.     

中国东南部晚中生代-新生代玄武岩与壳幔作用

中国东南部的火山活动在早中生代时期仅有很小规模,晚中生代最早的、较大规模的岩浆活动始于中侏罗世早期,至早白垩世是火山岩浆活动的鼎盛期,在近100个Ma的时间内形成了大面积分布的晚中生代火山-侵入岩,而在新生代则以面积较小的玄武岩浆喷出活动为主,局限分布于沿海一带。以晚中生代湘南、赣南和闽西南的近EW向火山岩带和浙、闽沿海地区的近NNE向火山岩带,以及新生代近NNE向火山岩带为研究对象,对这些火山岩的地球化学特征对比研究,结合时空分布,讨论了它们的起源及其与壳幔相互作用的关系,以及它们形成的构造环境,其结果显示,EW向晚中生代火山岩带（180～170Ma）的西段玄武岩独立产出,且明显属碱性系列;而中段和东段玄武岩和流纹岩伴生,其中的玄武岩均为亚碱性系列的拉斑玄武岩。它们形成于板内拉张构造环境,是中国东南部特提斯构造域向太平洋构造域转换、晚中生代大规模岩浆作用的序幕。研究表明,该火山岩带自西向东表现出不同程度的壳幔相互作用,玄武岩在成岩过程中有少量陆壳组分加入。NNE向晚中生代火山岩带（130～90Ma）主要为流纹质岩石,安山岩和玄武岩很少。即使是双峰式火山岩也以酸性岩为主,玄武岩仅占全部火山岩体积的30％以下。其中的玄武岩主要属钙碱性系列,少数属拉斑系列。它们形成于火山弧构造环境,是中国东南部受太平洋构造域影响发生大规模火山岩浆作用的主旋律。其中玄武岩岩浆成分受到了较高程度的陆壳物质混染,同时代的中性火山岩是由底侵的玄武岩岩浆和陆壳物质来源的酸性岩浆发生岩浆混合作用而形成的,反映了强烈的壳幔相互作用。NNE向新生代火山岩带,分布在浙闽沿海,以碱性系列玄武岩为主,均含幔源包体,并受NNE向大陆边缘断裂构造的控制。它们形成于板内裂谷环境,是中国东南沿海由晚中生代火山弧构造环境转换为新生代板内裂谷环境的标志,起源于软流圈地幔,并有EMII岩石圈地幔的混合组分,但基本没有受到陆壳物质的混染。     

Genesis of zircon megacrysts in Cenozoic alkali basalts and the heterogeneity of subcontinental lithospheric mantle, eastern China

Zircon megacrysts are found in alluvial deposits associated with Cenozoic basalts from Changle in Shandong Province, Mingxi in Fujian Province and Penglai in Hainan Province within the coastal area of eastern China. They are colourless, transparent to light brown–maroon, and some of them are up to 16 mm long. U–Pb ages of zircon megacrysts from Changle, Mingxi and Penglai are 19.2?±?0.7 Ma, 1.2?±?0.1 Ma and 4.1?±?0.2 Ma respectively, slightly older than the eruption ages of their corresponding host rocks (16.05–18.87 Ma, 0.9–2.2 Ma, 3 Ma). ε_Hf(t) values of zircon megacrysts are 9.02?±?0.49, 6.83?±?0.47, 4.46?±?0.48 for Changle, Mingxi and Penglai, respectively, which indicates their mantle origin. We suggest that the zircon megacrysts originated from metasomatised lithospheric mantle and were later brought up quickly by the host basaltic magma. The euhedral forms, uniform internal structure and chemical homogeneity within a single grain suggest crystallization under stable conditions. Pronounced positive Ce anomalies and negligible Eu anomalies suggest oxidizing conditions and little or no fractional crystallization of plagioclase. The differences in Hf-isotope compositions among the zircon megacrysts from different localities are consistent with the Sr-Nd-Pb isotopic compositions of their respective host basalts. This indicates that the host basalts acquired their isotopic signatures from the lithospheric mantle from which the zircon megacrysts derived. These data document the lateral compositional heterogeneity in the upper mantle beneath eastern China. Like mantle xenoliths, zircon megacrysts also have the potential to fingerprint the composition and evolution of the subcontinental lithospheric mantle.