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1.
南秦岭城口火山岩锆石LA-ICP-MS U-Pb定年和地球化学研究 总被引：3，自引：0，他引：3
南秦岭大巴山城口断裂带出露一套玄武安山岩、安山岩组合,火山岩锆石LA-ICP-MS U-Pb定年测试结果为716±4Ma,表明其为新元古代岩浆产物;岩石地球化学研究表明火山岩富集轻稀土元素,原始地幔标准化微量元素蛛网图显示以富集大离子亲石元素Cs、Ba、Th、U及高场强元素分异为特征,Nb、Ta强烈亏损以及低的Ti(Ti O_20.85%)含量,与典型的岛弧火山岩相似;微量元素La/Nb、Th/Yb及Hf/Ta比值特征也显示岛弧岩浆属性,相对高的Zr/Y、Ta/Yb和低的Zr/Nb比值区别于大洋岛弧火山岩,具有明显的大陆亲缘性,表明城口火山岩形成于陆缘岛弧环境。综合已有的地质、地球化学及同位素年代学研究表明新元古代晚期扬子板块北缘及南秦岭地区为一活动陆缘岩浆杂岩弧,暗示中国华南板块很可能位于Rodinia超大陆的边缘部位。 相似文献
2.
内蒙古乌拉特中旗北七哥陶辉长岩SHRIMP锆石 U-Pb年龄、地球化学特征及其地质意义 总被引：12，自引：3，他引：9
内蒙古乌拉特中旗温更地区北七哥陶辉长岩岩体由橄榄辉长岩和角闪辉长岩组成,主要造岩矿物为橄榄石、辉石、斜长石及角闪石等.锆石SHRIMP U-Pb同位素定年结果表明,橄榄辉长岩形成于269±8Ma,为晚古生代华北板块北缘岩浆活动的产物.橄榄辉长岩和角闪辉长岩具有相似的稀土元素、微量元素以及同位素特征,即:轻稀土元素( LREE)富集的右倾平滑配分模式;大离子亲石元素(LILE)K、Sr、Ba明显富集,高场强元素(HFSE) Nb、Ta、U、Th相对亏损,但Zr-Hf不亏损;87Sr/86Sr(t)平均值分别为0.706776和0.706960,εNd(t)平均值分别为-8.8和-8.9,206pb/204Pb、207pb/204Pb、208Pb/204Pb比值的平均值分别为17.2019和17.2277、15.4252和15.4524、37.3082和37.4724,在s7 Sr/86Sr(t)-143Nd/144 Nd (t)图解上,北七哥陶辉长岩都落在了EMI型富集地幔附近.根据以上事实,结合区域资料表明,橄榄辉长岩和角闪辉长岩产于后碰撞的构造环境,并且来自相同的岩浆源区,主要继承了华北陆块内部EMI型富集地幔,可能受到了古亚洲洋俯冲消减过程中再循环下地壳组分对岩石圈地幔的改造. 相似文献
3.
为查明柴达木盆地北缘西段早石炭世沉积物来源和构造背景,本次研究采集小赛什腾山怀头他拉组沉积岩进行碎屑岩锆石U- Pb年代学和全岩微量元素地球化学分析。研究表明：测试样品微量元素蛛网图呈平坦型,富Th、U、Hf,贫Co、Sc、Ni、V元素;砂岩轻重稀土元素分馏明显,属轻稀土富集型,具有中等负Eu异常;Cr/Zr、Sm/Nd、Th/Sc及Th/U等微量元素比值和判别图版显示研究区怀头他拉组为上地壳长英质物源区。沉积岩微量元素、稀土元素含量及特征比值显示,研究区样品与大陆弧环境砂岩具有极为相似的地球化学特征,相关构造环境投图同样表明怀头他拉组沉积环境以大陆弧为主,兼有主动大陆边缘特征。怀头他拉组碎屑锆石U- Pb年龄可划分出3个年龄区间,480～402 Ma,1493～900 Ma和1908～1803 Ma。年龄谱呈早古生代单峰值特征,峰值年龄为414 Ma,反映物源区与柴北缘加里东期构造带内早古生代晚期的岩浆作用关系密切。结合前人区域上古地理、古水流证据,综合分析认为小赛什腾山下石炭统怀头他拉组物源主要来自于柴北缘高压—超高压变质带。 相似文献
4.
小兴安岭北部二龙山林场辉长岩的主量、微量和稀土元素的测试分析结果显示: 二龙山辉长岩为钙碱性系列、偏铝质岩石; δEu 正异常,Sr 元素含量富集明显,具有堆晶辉长岩特征; Rb /Sr、Nb / Ta、LILE/HFSE、Th /Ta、Nb /U 和Nb /La 比值特征均显示,辉长岩岩浆来自受到俯冲流体交代的地幔源区。Nb /Zr、Th /Nb、Th /Ta 和Ta /Hf 比值特征及对Th /Hf --Ta /Hf 构造环境判别图解投点表明,二龙山辉长岩形成于陆内拉张环境。 相似文献
5.
牛鼻子梁地区首次发现的高镁闪长岩对于探讨柴北缘地区岩石圈地幔演化历史具有重要意义.为确定该类岩石成因及地球动力学过程,对其开展矿物学、岩石主-微量元素分析、锆石U-Pb定年和Hf同位素分析工作.岩石地球化学特征显示,岩石均为钙碱性岩石,具有富Mg（Mg#=62~72）、Cr、Ni、LREE（LREE/HREE=2.84~4.61）值、低FeOT/MgO（0.70~1.12）比值特征,属于高镁闪长岩;所有样品均表现出富集大离子亲石元素（Rb、Ba、Th、U、K）和LREE,而相对亏损高场强元素Nb、Ta、Ti、P和HREE,与典型的"赞岐岩"地球化学特征一致;锆石U-Pb同位素年代学研究表明岩石形成时代为388 Ma,为中泥盆世岩浆作用的产物.锆石Hf同位素特征显示岩石εHf（t）均为正值（4.4~11.6）,表明岩浆起源于亏损地幔.结合区域构造演化过程认为,牛鼻子梁高镁闪长岩是由早古生代（540~520 Ma）消减带流体交代地幔楔后的富集地幔经历晚古生代（400~388 Ma）岩石圈伸展作用部分熔融的产物. 相似文献
6.
扬子陆块西缘古元古代基性侵入岩LA-ICP-MS锆石U-Pb年龄和Hf同位素及其地质意义 总被引：7，自引：2，他引：5
扬子陆块西缘康滇南北向构造带内发育大量古元古代基性岩脉(墙),它们对于认识扬子陆块早期的构造演化具有重要意义.对四川会理地区侵入到元古界通安组内的辉长岩进行LA-ICP-MS锆石U-Th-Pb同位素测定,获得的207pb/206Pb加权平均年龄为1694Ma±16Ma(MSWD=0.9),代表了该辉长岩的形成和侵位时代,这一结果指示会理地区通安组应为古元古代地层.辉长岩全岩地球化学具有类似于N-MORB的特征.辉长岩锆石初始(176H f/177Hf)i值为0.281881～0.281982,对应的εHf(t)为6.2～9.8,单阶段亏损地幔Hf模式年龄tDM1为1738～1883Ma,平均值为1803Ma.这些数据表明古元古代辉长岩来源于亏损地幔,指示古元古代晚期扬子西缘之下存在亏损地幔.结合扬子西缘大量古老的碎屑锆石,推测扬子陆块西缘存在太古宙—古元古代的结晶基底.与扬子陆块西缘古元古代晚期基性侵入岩形成有关的幔源岩浆事件明显晚于扬子陆块古元古代碰撞造山及造山后的伸展作用,记录了扬子陆块古元古代晚期一次伸展过程,可能是Columbia超大陆裂解作用在扬子陆块的响应. 相似文献
7.
北秦岭新元古代前属于扬子板块的地球化学证据 总被引：18，自引：1，他引：17
秦岭是扬子板块和华北陆块间的复合造山带,其中存在两个古缝合带,北面的新元古代到早古生代商－丹缝合带介于北秦岭和南秦岭之间,南面的晚古生代勉－略缝合带形成于南秦岭与扬子陆块北缘之间,属于确知的扬子陆块内部打开形成的类型。北秦岭在地壳增生历史,元古宙上地慢性质,以及元古宙以来地幔相对富Nb、Ta、Cu,高Rb／Sr、Ba／Sr、Ba／La、Th／La、Nb／Ta比值和相对贫Fe、Mo方面均与南秦岭和扬子陆块北段一致。而与华北板块南段明显不同。变玄武岩类的Pb同位素三维空间拓扑图和铀εNd（t）－206Pb／204Pb图显示,区域一级地球化学界面位于北秦岭与华北陆块的分界处,二级界面才是商丹－缝合带。构造侵位于该带中的松树沟蛇绿岩<1000 Ma士)中已发现并存着N—MORB和E—MORB型变拉斑玄武岩。表明它们的岩浆分别来自亏损地幔和深部地幔热柱源区。松树沟蛇绿岩与勉,略蛇绿岩中的N—MORB型岩石具有与此相似的同位素组成和特征元素对比值,暗示松树沟蛇绿岩所代表的古洋壳也应属于扬子板块内部型。加之,新元古代之前秦岭只存在裂谷系而无板块结合带,故可确定北秦岭原来应属于扬子板块的组成部分。对秦岭群和宽坪群变拉斑玄武岩及松树沟E—MORB和N—MIORB进行地球化学对比的结果,既能够支持北秦岭是在扬子板块的洋壳洋岛基础上发展形成的微陆块的推断,又可解释北秦岭幔源岩石具有特高Th／La、Yb／Hf、Sc／Th比值和壳幔更富于放射成因钳的原因。此外。对本研究结果在秦岭造山带发展动力学方面的意义也进行了初步讨论。 相似文献
8.
柴北缘冷湖盐场北山镍铜矿区发育辉长岩和角闪辉长岩;属亚碱性岩石系列。球粒陨石、 原始地幔标准化曲线呈两组特征;但配分型式基本一致;反映其来自同一源区。稀土标准化曲线表现为弱右倾型;Eu基本无异常;说明斜长石分离结晶作用不明显。Rb、 Nb、 Zr、Cr等微量元素丰度及比值具有近似平行部分熔融的演化趋势。结合岩体Mg#值和岩体固结指数（SI）高等特点;揭示原始岩浆具有幔源原生玄武岩浆特征;认为其成因与俯冲板片流体交代地幔楔源区的部分熔融有关;而且;Nb、 Zr、 Y元素丰度表明辉长岩源区为过渡型地幔。另外;两类岩体强烈亏损Nb、 Ta、 Zr、 Hf、 Ti等高场强元素（HFSE）;富集Ba、 Th、 U、 Pb等大离子亲石元素;反映明显的消减带和岛弧环境岩浆岩典型特征。LA-ICPMS锆石U-Pb测年结果表明辉长岩形成于254±3 Ma;结合该时期区域地质构造背景;认为柴北缘晚二叠世处于俯冲作用之下的岛弧构造环境;具有活动大陆边缘性质。 相似文献
9.
丹凤地区秦岭岩群片麻岩锆石U-Pb年龄:北秦岭地体中-新元古代岩浆作用和早古生代变质作用的记录 总被引：12，自引：7，他引：5
秦岭岩群被认为是出露于北秦岭地体内最古老的前寒武纪基底岩石,记录了北秦岭造山带的地壳形成和演化历史。本文报道丹凤-西峡地区五件秦岭岩群片麻岩锆石U-Pb年龄结果,限定其形成和变质时代,探讨北秦岭地体的构造归属。定年结果表明,岩浆成因锆石颗粒的年龄集中在1400～1600Ma左右和850～950Ma左右,记录两期主要岩浆活动。6粒锆石具有变质成因特征,低Th/U比值(0.03),206Pb/238U年龄变化在510～465Ma之间,加权平均值477±18Ma。这一古生代变质叠加时代与北秦岭地体南北缘高压变质作用时代基本一致,说明秦岭岩群遭受到北秦岭造山带俯冲-碰撞造山过程的变质作用。秦岭岩群主要形成于中元古代晚期至新元古代早期,基底岩石缺乏早元古代和太古代岩浆活动的记录。在岩浆作用时代上,北秦岭地体与广泛发育新元古代中-晚期岩浆作用的扬子陆块北缘有差别,也不同于晚太古代-早元古代的华北陆块南缘,可能是中-新元古代形成的独立微陆块。 相似文献
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鲁西早白垩世岩石圈地幔的属性:大昆仑辉长岩和辉绿岩年代学、岩石地球化学和Sr-Nd-Pb-Hf同位素制约 总被引：3，自引：3，他引：0
大昆仑辉长岩和辉绿岩锆石LA-ICP-MS U-Pb年代学、锆石Hf同位素和全岩地球化学及全岩Sr-Nd-Pb同位素的研究为探讨鲁西地区早白垩世岩石圈地幔的属性提供了制约。结果表明,大昆仑辉长岩中少量锆石和辉绿岩中锆石发育条痕状吸收,具有相对高的Th/U比值(0.11~3.12),暗示它们均为岩浆成因,辉长岩中多数为岩浆成因的捕获锆石。辉长岩和辉绿岩中岩浆锆石的~(206)Pb/~(238)U加权平均年龄分别为132±3Ma和112±1Ma;辉长岩中捕获锆石的谐和年龄主要介于2469~1752Ma之间,暗示古老地壳物质的存在。辉长岩和辉绿岩整体具有低Si O_2(49.08%~52.61%)、高MgO(4.52%~9.67%)、Na_2O含量(2.58%~3.49%)以及高Mg~#值(45~65)特征;富集轻稀土元素和大离子亲石元素(Rb、Ba、Th)、贫重稀土元素和高场强元素(Nb、Ta、Zr和Hf),其(La/Yb)_N=8.98~10.2,Eu负异常不明显(δEu=0.83~0.93)。辉长岩的初始~(87)Sr/~(86)Sr比值变化于0.7046~0.7060之间,ε_(Nd)(t)值介于-16.71~-15.54之间,~(206)Pb/~(204)Pb、~(207)Pb/~(204)Pb和~(208)Pb/~(204)Pb初始比值分别为16.596~16.776、15.255~15.290和36.328~36.648。辉绿岩中岩浆锆石的ε_(Hf)(t)值介于-12.0~-2.5之间。上述结果表明,大昆仑辉长岩和辉绿岩形成于早白垩世,与华北克拉通东部早白垩世岩石圈减薄的峰期时间一致;起源于受华北克拉通古老下地壳物质改造的富集岩石圈地幔的部分熔融,形成于岩石圈减薄的伸展构造背景。 相似文献
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西藏玛依岗日地区侵入脉岩为辉长岩,通过采集辉长岩样品,观察显微照片,并进行主量元素、微量元素和稀土元素含量测试。结果表明：Na2O与K2O含量变化范围不大,全碱(K2O+Na2O)含量为186%～411%,样品K2O/Na2O值的范围为025～066。岩石富集轻稀土、亏损重稀土,铕无正负异常。总体富集Hf、La、Nd、Ti,亏损P、Yb、Y等元素。地球化学特征表明其形成于陆内裂谷环境,岩浆来源于富集地幔,受到硅铝质地壳物质的混染。结合辉长岩围岩为晚石炭世—早二叠世浅变质岩系以及早二叠世晚期之后的地层中不发育岩墙群的事实,而且根据前人对藏北羌塘南部地区基性岩墙群为晚石炭世—早二叠世的年龄约束,推断研究区内南北向辉长岩可能为古特提斯洋拉张初期的产物。 相似文献
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北京燕山地区薛家石梁杂岩体特征、成因、源区性质及岩石圈减薄方式 总被引：14，自引：1，他引：14
薛家石梁杂岩体位于北京北山地区,在平面上呈北西向的椭圆状,主要由辉长岩、二长辉长岩、二长岩、正长岩和花岗岩组成。根据锆石SHRI MP定年结果为132·8~123·3Ma,形成于早白垩世早期。野外地质特征、矿物学特征、岩石学特征及地球化学特征表明,薛家石梁杂岩体中二长岩是二长辉长岩岩浆与正长岩岩浆混合作用的产物,从辉长岩岩浆到二长辉长岩岩浆经历了结晶分异作用。薛家石梁杂岩体中正长岩具高Sr,低Y及Eu正异常特征,推测其可能来源于加厚陆壳的底部。薛家石梁杂岩体中辉长岩中Mg#值为65,w(Nb)/w(U)值为37·8,这些特征暗示其可能为原生岩浆。辉长岩中ε(Nd)值为-6·5,表明其源区岩石不具亏损地幔特征;而辉长岩具富集Pb、Ti、Nb正异常,Hf的负异常,与EMI型富集地幔特征(具Nb、Hf正异常及Pb的负异常)不一致;辉长岩中Rb、Th、Nb、U、La、Ce元素含量比EMI型富集地幔低一个数量级;杂岩体中N(87Sr)/N(86Sr)与N(206Pb)/N(204Pb)值具正相关关系也表明不具交代富集型地幔特征。因此,我们认为辉长岩岩浆源区应为软流圈地幔,而不是富集型地幔(EMI)。辉长岩中ε(Nd)的负值是辉长岩岩浆与太古宙下地壳相互作用的结果。因此,我们认为中国东部岩石圈减薄的主要机制是岩石圈的拆沉作用。 相似文献
13.
ZHANG Jiheng GE Wenchun WU Fuyuan LIU Xiaoming College of Earth Sciences Jilin University Changchun Jilin Institute of Geology Geophysics Chinese Academy of Sciences Beijing Key Laboratory of Continental Dynamics 《《地质学报》英文版》2006,80(1):58-69
1 Introduction Mesozoic volcano-intrusive rocks are widely distributed in the Da Hinggan Range of northeastern China, and are considered as one of the most spectacular geological sights in eastern Asia. Recently, studies on granites with high εNd(t) values and Phanerozoic crustal growth in the Centra Asian Orogenic Belt have greatly promoted fundamental research into the geology of this area (Jahn et al., 2000, 2001, 2004; Wu et al., 2000, 2002, 2003). However, work on the eruption time,… 相似文献
14.
Geological observations in combination with previously published and new isotopic data allowed us to reconstruct the history of geological events that eventually gave rise to the formation of the Berdyaush pluton situated on the western slope of the South Urals: (1) emplacement of gabbro into Lower Riphean sedimentary rocks (1410–1390 Ma); an enriched mantle source of gabbro arising in the Archean or Paleoproterozoic; (2) formation of granitic melt in the lower crust; Archean TTG association subsequently enriched in K and correlative elements as a result of interaction with enriched mantle-derived magmas and related fluids was a magma source; mixing of mantle and crustal magmas in the course of their synchronous ascent with formation of hybrid intrusive rocks; injections of mafic and hybrid melts into incompletely solidified granite; fragmentation of such injections with the formation of melanocratic nodules; emplacement of basic dikes into the cooled granite—all these events took place 1410–1360 Ma ago; (3) discrete episodes of partial melting of enriched mantle source with waning intensity; formation of minor volumes of melt, which solidified under auto- and paraautochthonous conditions as local domains highly enriched in incompatible elements (1360–1270 Ma); (4) partial melting of those domains resulting in the formation of minor nepheline syenite intrusions (915–800 Ma), containing relict zircon grains dated at >1270 Ma; (5) injections of mantle-derived alkaline melt contaminated with crustal granitic material as microsyenite and syenite porphyry dikes (700–500 Ma ?). Thus, the Berdyaush pluton is a projection of a local domain of mantle and crustal magma generation, which periodically resumed its activity over almost a billion years. 相似文献
15.
中天山卡瓦布拉克地区侵入岩类广泛发育,并多处被中-基性岩脉穿插。LA-ICP-MS锆石U-Pb测年获得闪长岩和辉长岩脉年龄分别为296.1±2.5 Ma(MSWD=1.4),299.5±2 Ma(MSWD=1.07),均侵位于早二叠世。岩石学和岩石地球化学分析结果表明该区中-基性岩脉具有富集轻稀土元素(LREE)和大离子亲石元素(Rb,U,Th)、亏损高场强元素(Nb,Ta,Ti)的地球化学特征,SREE为69.19~234.62,LREE/HREE=3.97~11.18。闪长岩脉锆石(176Hf/177Hf)值为0.280 618~0.283 329,对应的εHf(t)值为-14.57^+25.06。研究数据表明,该区中-基性岩脉可能起源于亏损岩石圈地幔,原始岩浆在侵位过程中发生了分离结晶作用,同时还受到了地壳混染作用的影响。基于卡瓦布拉克地区中-基性岩脉的野外地质特征和地球化学分析结果,并结合区域地质资料,认为它们形成于南天山洋闭合之后的后碰撞伸展构造背景。 相似文献
16.
The Balmuccia alpine lherzolite massif is a fragment of subcontinental lithospheric mantle emplaced into the lower crust 251 Ma ago during the final, extensional phase of the Hercynian orogeny. The Balmuccia massif consists largely of lherzolite, with subordinate harzburgite and dunite, and an array of dike rocks formed in the mantle before crustal emplacement. Dike rocks include websterite and bronzitite of the Cr-diopside suite, spinel clinopyroxenite and spinel-poor websterite of the Al-augite suite, gabbro and gabbronorite of the late gabbro suite, and hornblendite of the hydrous vein suite. The dike rocks display consistent intrusive relationships with one another, such that Cr-diopside suite dikes are always older than dikes and veins of the Al-augite suite, followed by dikes of the late gabbro suite and veins of the hydrous vein suite. Phlogopite (phl) veinlets that formed during interaction with the adjacent crust are the youngest event. There are at least three generations of Cr-diopside suite dikes, as shown by crosscutting relations. Dikes of the Al-augite suite form a polybaric fractionation series from spinel clinopyroxenite to websterite and feldspathic websterite, which crystallized from aluminous alkaline magmas at relatively high pressures. The late gabbro suite of dikes intruded at lower pressures, where plagioclase saturation occurred before significant mafic phase fractionation. Hornblendite veins have distinct compositional and isotopic characteristics, which show that they are not related to either the Al-augite suite or to the late gabbro dike suite. Cr-diopside suite dikes have Nd and Sr isotopic compositions similar to those of the host lherzolite and within the range of compositions defined by ocean–island basalts. The Al-augite dikes and the hornblendite veins have Sr and Nd isotopic compositions similar to those of Cr-diopside suite lherzolite and websterite. The late gabbro dikes have Nd and Sr isotopic compositions similar to mid-ocean ridge basalt (MORB) asthenosphere. Lead isotopic compositions for all of the samples fall in the present-day MORB field on the 208Pb/204Pb vs. 206Pb/204Pb diagram but are displaced above this field on the 207Pb/204Pb vs. 206Pb/204Pb diagram. There is overlap in the data between the Cr-diopside suite and the Al-augite and hydrous vein suites, with the exception that the Cr-diopside websterite dikes have more radiogenic Pb than any of the other samples. In Pb–Pb space as well, the late gabbro suite has the least radiogenic isotopic compositions, reflecting a change in magma source region during uplift. These data show that tectonic thinning of subcontinental lithospheric mantle during extension caused a change in the source regions of mantle-derived magmas from an ocean island basalt (OIB)-like lithosphere to the underlying MORB asthenosphere. They also demonstrate that the upper mantle acquires its heterogeneous isotopic character through several different processes, including in situ radiogenic growth, addition of asthenospheric melts, dike-wall rock ionic exchange, redistribution of the lithospheric dike and vein materials by melting, and in the late stages of emplacement, assimilation of crustal materials. 相似文献
17.
达拉库岸镁铁-超镁铁质岩体位于东昆仑造山带南带之喀拉米兰晚古生代沟弧系,主要由二辉橄榄岩、单辉橄榄岩、橄榄二辉岩、单辉辉石岩和辉长岩组成。辉长岩的锆石U-Pb谐和年龄为244.4±1.5Ma,属于中三叠世。岩石普遍弱富集稀土元素和大离子亲石元素(Rb、Ba、Sr),亏损不相容元素(Nb、Ta)。岩体原生岩浆为高镁拉斑玄武质岩浆(Mg O 11.4%,Fe O10.8%)。元素地球化学和Nd、Sr同位素组成特征表明岩浆源区为富集岩石圈地幔,岩浆运移和侵位过程中遭受不同程度地壳物质的同化混染作用。依据橄榄石组分模拟获得橄榄石结晶过程中母岩浆达到硫饱和,并发生硫化物的熔离作用。从岩体特征、矿石结构、原生岩浆性质、深部硫化物熔离和物探信息等方面综合分析,岩体具有形成岩浆型铜镍硫化物矿床的良好条件。 相似文献
18.
Christian Creixell Miguel Ángel Parada Diego Morata Pierrick Roperch César Arriagada 《International Journal of Earth Sciences》2009,98(1):177-201
Five mafic dike swarms between 30° and 33°45′S were studied for their geochemical signature and kinematics of magma flow directions
by means of AMS data. In the Coastal Range of central Chile (33°−33°45′S), Middle Jurassic dike swarms (Concón and Cartagena
dike swarms, CMDS and CrMDS, respectively) and an Early Cretaceous dike swarm (El Tabo Dike Swarm, ETDS) display the presence
of dikes of geochemically enriched (high-Ti) and depleted (low-Ti) basaltic composition. These dikes show geochemical patterns
that are different from the composition of mafic enclaves of the Middle Jurassic Papudo-Quintero Complex, and this suggests
that the dikes were injected from reservoirs not related to the plutonic complex. The mantle source appears to be a depleted
mantle for Jurassic dikes and a heterogeneous-enriched lithospheric mantle for Cretaceous dikes. In the ETDS, vertical and
gently plunging magma flow vectors were estimated for enriched and depleted dikes, respectively, which suggest, together with
variations in dike thickness, that reservoirs were located at different depths for each dike family. In the Elqui Dike Swarm
(EDS) and Limarí Mafic Dike Swarm (LMDS), geochemical patterns are similar to those of the mafic enclaves of the Middle Jurassic
plutons. In the LMDS, east to west magma flow vectors are coherent with injection from neighbouring pluton located to the
east. In the EDS, some dikes show geochemical and magma flow patterns supporting the same hypothesis. Accordingly, dikes do
not necessarily come from deep reservoir; they may propagate in the upper crust from coeval shallow pluton chamber.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
19.
内蒙古扎赉特旗辉长岩-闪长岩地球化学特征和LA-ICP-MS锆石U-Pb年龄 总被引：1，自引：0，他引：1
扎赉特旗地区发育的辉长岩-闪长岩属钙碱性岩石系列。岩石相对富集LREE、大离子亲石元素（K、Rb、Ba和Sr）及u,亏损高场强元素（Th、Ta、Nb和Ti）,类似于岛弧环境产物。推测其源区为岩石圈地幔,原生岩浆为幔源物质部分熔融产生,在上升过程中遭受微弱地壳混染。用LA-ICP-Ms同位素测定方法．测得其中变辉绿岩、角闪辉长岩和辉长闪长岩的锆石206Pb／238U年龄平均值分别为317．3Ma±1．1Ma（30个数据点）、328．1Ma±1．3Ma（29个数据点）、325．2Ma±0．9Ma（32个数据点）,为首次在扎赉特旗地区中基性岩体中获得较早的高精度岩体侵位年龄,指示扎赉特旗-带在早石炭世末期存在洋壳俯冲作用,为进一步研究二连浩特-贺根山碰撞拼合带东延至扎赉特旗-带的形成与演化提供了新的证据。 相似文献
20.
A. A. Arzamastsev R. V. Vesolovskiy A. V. Travin D. S. Yudin B. V. Belyatsky 《Petrology》2017,25(1):42-65
This paper focuses on the occurrences of tholeiitic magmatism in the northeastern Fennoscandian shield. It was found that numerous dolerite dikes of the Pechenga, Barents Sea, and Eastern Kola swarms were formed 380–390 Ma ago, i.e., directly before the main stage of the Paleozoic alkaline magmatism of the Kola province. The isotope geochemical characteristics of the dolerites suggest that their primary melts were derived from the mantle under the conditions of the spinel lherzolite facies. The depleted mantle material from which the tholeiites were derived shows no evidence for metasomatism and enrichment in high fieldstrength and rare earth elements, whereas melanephelinite melts postdating the tholeiites were generated in an enriched source. It was shown that the relatively short stage of mantle metasomatism directly after the emplacement of tholeiitic magmas was accompanied by significant mantle fertilization. In contrast to other large igneous provinces, where pulsed intrusion of large volumes of tholeiitic magmas coinciding or alternating with phases of alkaline magmatism was documented, the Kola province is characterized by systematic evolution of the Paleozoic plume–lithosphere process with monotonous deepening of the level of magma generation, development of mantle metasomatism and accompanying fertilization of mantle materials, and systematic changes in the composition of melts reaching the surface. 相似文献