五大连池钾质火山岩中的壳源捕虏体特征及地质意义

黑龙江省五大连池钾质火山岩石中普遍含有壳源捕虏体和捕虏晶,并多赋存于火山集块、浮岩砾、火山渣等各级火山碎屑物及盾状台地的表皮相到内部相火山熔岩中。花岗岩质捕虏体一般大小为5～50cm,捕虏晶一般为0.2～5mm,成分以二长花岗岩为主,少见花岗闪长岩及黑云母英云闪长岩和少量砂岩捕虏体。石英、斜长石、少数钾长石捕虏晶见于各期火山碎屑(物)和熔岩中,其中以石英捕虏晶最为常见。壳源捕虏体中的代表性矿物及浅色玻璃电子探针分析结果表明,火山岩SiO2偏高是岩浆上涌喷发过程中捕获了大量壳源物质的结果。五大连池火山群富钾火山岩岩石化学、地球化学长期保持均一,说明其岩浆直接来自EMⅠ型钾质地幔,岩浆在上升过程中遭受了地壳物质的明显混染。     

平潭和漳州深成杂岩中斜长石捕虏晶与岩浆混合作用

在闽东南平潭和漳州火成杂岩中,广泛发育岩浆混合现象,表现为花岗质岩石中存在辉长－闪长质同深成岩墙和淬冷岩石包体。花岗质和闪长质岩石中普遍存在Ａｎ＞７０％的斜长石捕虏晶。这种成分的斜长石是辉长岩特有的,而不是任一种花岗岩的斑晶。在斜长石捕虏晶四周,都有与花岗岩中的斜长石成分相当的斜长石加生膜。斜长石捕虏晶可分为自形的、熔融状、筛孔状和碎片状等四类,它们各自形成于不同的动力环境     

西昆仑阿卡阿孜山杂岩体的特征和成因

阿卡阿孜山杂岩体位于西昆仑昆南地体南侧,被新藏公路横切出一条南北长约2 km的剖面。在剖面范围内可见二长闪长岩、石英二长闪长岩、花岗闪长岩、二长花岗岩、正长花岗岩和碱长花岗岩等多种岩石类型出露。通过详细研究岩体的野外地质特征、地球化学和同位素地球化学特征发现：岩体中出现不平衡矿物组合;镁铁质微粒包体中可见石英和长石捕虏晶;各岩石样品的痕量元素配分型式呈现相似性;岩体的Sr、Nd、Pb同位素体系同时具有地幔和下地壳的贡献等,认为岩体形成于壳幔岩浆混合作用,幔源岩浆底侵作用可能是混合作用的直接原因。由此推测,幔源岩浆底侵作用是西昆仑地区印支晚期岩浆活动的重要诱发机制。     

北大巴山碱质基性—超基性潜火山杂岩的辉石矿物研究

北大巴山碱质基性-超基性潜火山杂岩中有7种岩石含有新鲜的单斜辉石,它们分属于透辉石、普通辉石及霓辉石。单斜辉石可划分为5种成因类型:(1)斑晶、微斑晶及微晶;(2)深源捕虏晶;(3)半同源捕虏晶;(4)异源捕虏晶;(5)地幔型捕虏晶,本文涉及前4类辉石。单斜辉石的研究表明:(1)7种含辉石的岩石为同源岩浆结晶分异作用的产物,源岩浆为碱性-过碱性幔源岩浆。(2)初始岩浆形成于77km以下深度,上升过程中岩浆曾在3个不同深度储积。(3)岩浆上升至近地表处,在冷凝固结前曾有多次潜火山隐爆活动发生。(4)霓辉石捕虏晶的出现代表区内存在另一种碱基性岩浆活动。(5)辉石成分指示碱质基性-超基性次火山杂岩形成于陆边板内裂陷带。     

小兴安岭晚石炭世花岗岩岩浆混合作用的岩相学证据及其地质意义

小兴安岭晚石炭世花岗岩具有明显的岩浆混合特征。岩体中暗色岩浆包体发育,主要为细粒闪长质岩浆包体,包体形态多样、大小不一,与寄主岩石呈截然、模糊或过渡关系。包体的矿物组合明显不平衡,如出现了寄主岩石中的碱性长石捕虏晶,有时可见其具暗色矿物镶边,发育针状磷灰石。这表明小兴安岭晚石炭世花岗岩的岩浆混合表现为基性岩浆和酸性岩浆的混合。这为探讨这些花岗岩的成因提供了岩石学依据,同时也暗示晚古生代佳木斯—松嫩古陆可能发生过地壳的垂向生长。     

新疆西准噶尔夏尔莆岩体中微粒镁铁质包体特征及意义

夏尔莆岩体寄主岩石为闪长岩-花岗闪长岩-二长花岗岩组合,其中镁铁质微粒包体十分发育.包体个体大小悬殊.多密集成群、成带状分布,具明显塑性变形特征.包体与寄主岩石或界线截然或渐变过渡.包体中发育斜长石异常环带、针状磷灰石和来自寄主岩石中的长石捕虏晶,包体中不平衡矿物间的共生现象普遍.岩相学特征表明为基性岩浆和酸性岩浆经岩浆混合作用而成.这一新认识为探讨夏尔莆岩体及达尔布特花岗岩带成因提供新佐证.     

江西相山潜火山岩中淬冷包体的发现及其成因机制探讨

在江西相山大型塌陷式火山盆地北部的潜火山岩岩墙中，笔者发现了闪长质的岩石包体，这种包体具典型的反向脉及淬冷边，且淬冷边内含有大量针状磷灰石。在包体内部或包体与寄主岩的边界均见有钾长石及斜长石捕虏晶，这种捕虏晶是包体岩浆从寄主岩岩浆中捕获的，常被熔蚀成筛状或浑圆状。包体与寄主岩（次斑状花岗闪长岩）的稀土元素曲线和不相容元素蛛网图的形态非常相似。因此，相山潜火山岩岩墙中的闪长质岩石包体是不同成分、不同温度的岩浆经对流及不均一岩浆混合作用而形成，在成因类型上属淬冷包体。     

辽东中生代晚期和古近纪玄武岩及深源捕虏晶--对岩石圈地幔性质的制约

辽东地区玄武岩的K-Ar定年结果表明,曲家屯玄武岩形成于晚白垩世,K-Ar年龄为81．58±2．46Ma;乱石山子玄武岩形成于古近纪,K-Ar年龄为58．36±1．64Ma。本区玄武岩含有丰富的橄榄石、单斜辉石和角闪石捕虏晶。乱石山子玄武岩中橄榄石捕虏晶的Mg^#值（79．5-88．5之间,平均值为84）较曲家屯玄武岩中橄榄石捕虏晶Mg^#值（77．0～79．8之间,平均值为78．4）偏高;单斜辉石捕虏晶为透辉石,其从核部到边部的Mg^#等变化趋势与橄榄石类似;斜方辉石捕虏晶为占铜辉石,其Mg^#值介于85．2-87．6之间,平均值为86．4。捕虏晶发育的环状裂隙、扭折带、矿物成分环带以及捕虏晶与主岩Mg^#值之间的不平衡均暗示它们为玄武质岩浆上升捕获的早期岩浆晶出矿物的堆晶体。玄武岩的岩石地球化学分析结果表明：（1）它们属于碱性系列,为碱性玄武岩,曲家屯玄武岩较乱石山子玄武岩贫硅、镁,富钙、铝,它们均具有原始岩浆的特征;（2）二者具有相似的稀土元素配分模式,但曲家屯玄武岩轻稀土元素总量更高,且轻重稀土元素分离程度高;（3）二者具有相似的Sr-Nd同位素组成,Isr和εNd（t）值分别介于0．7039～0．7045和＋1．60～＋3．69,反映了亏损的岩石圈地幔特征。     

小兴安岭鹤岗地区晚三叠世花岗岩闪长质包体特征及成因探讨

小兴安岭鹤岗地区晚三叠世花岗岩中普遍发育暗色细粒闪长质岩浆包体,大小不一、形态各异,边界有平滑状、棱角状,与寄主岩石边界呈现截然、模糊或过渡的特征.发育针状磷灰石.矿物组合明显不平衡,出现寄主岩碱性长石捕虏晶及碱性长石的黑云母暗色矿物眼镶边.异常的结晶顺序,说明包体是镁铁质岩浆注入长英质岩浆并发生混合、流动、搅拌后分散在寄主岩浆中的细小基性岩浆团固结而成.小兴安岭鹤岗地区晚三叠世花岗岩中识别出岩浆混合作用成因的MME型类型包体,对于从深部壳-幔相互作用角度来分析本区晚三叠世经历的大陆地壳垂向生长和演化具有重要意义.     

岩浆混合作用:来自岩石包体的证据

镁铁质岩浆与长英质岩浆之间的混合作用是导致壳幔混源花岗岩类形成的主要机制。暗色、细粒且具火成结构的岩石包体是指示岩浆混合作用存在的可靠证据。这些岩石包体具有下列特征:(1)包体常呈等轴状,表明包体岩浆曾以液态球滴状存在于寄主岩浆中;(2)由于基性岩浆温度恒高于酸性岩浆(温度超出约300℃),这类包体常具有淬冷边;(3)包体有时含有反向脉;(4)包体中能见到自寄主岩浆捕获的长石捕虏晶。进一步分析了三个典型的含暗色微粒包体的花岗质杂岩(平潭、普陀山、花山—姑婆山)研究实例,认为暗色微粒包体的形成,可用来自深部岩浆房的玄武质岩浆向浅部酸性岩浆房的注入作用来解释。     

Geochemistry of a Rapakivi Granite Suite in a Proterozoic Rift Trough in Beijing and Its Vicinity

Controlled by E-W-trending faults, a Proterozoic (1.4-1.8 Ga old) rapakivi granite suite was intruded inBeijing and the area to its east (within Hebei Province), forming three parallel belts of igneous rocks. Theisotopic, trace element and rare earth element geochemical data of a bimodal rock association made up ofanorthosite, gabbro and alkali basalt and olivine-bearing quartz-syenite, rapakivi granite and trachyte as wellas potassic A-type granites and anorogenic granites—— all suggest that there exists an incipient rift in thestudy area. Fractional crystallization of a mixed magma formed by the magma derived from the upper mantleand the magma derived by small degrees of fusion of the lower crust produced anorthosite cumulates. Thewater-deficient granitic magma was differentiated into a subalkaline series. When the fractional crystallizationwas incomplete, rhythmic eruptions took place.     

秦岭-昆仑造山型环斑花岗岩与世界典型环斑花岗岩的对比

通过秦岭-昆仑造山带中的环斑花岗岩同世界元古宙环斑花岗岩的岩石学、岩相学、岩石地球化学和构造环境等方面的对比研究发现,二者具有相同或一致的特征:具环斑结构,属准铝、高钾、富碱岩浆,具双峰式岩浆组合,形成于后碰撞环境,但其地球化学的某些指标、岩浆形成时代和出露的大地构造位置等有一定差异.世界元古宙环斑花岗岩的岩石化学及暗色矿物明显富铁,w(FeT)/w(FeT Mg)较高,多数在0.9以上,岩石成因类型多数是A型花岗岩,产在稳定地台区的边缘,而昆仑地区多数环斑花岗岩的w(FeT)/w(FeT MgO)＞0.8,亦较富Fe,且多数是A型花岗岩;秦岭地区的岩体铁指数相对较低,只有0.62,岩石成因类型的地球化学判据既有A型也有Ⅰ型花岗岩特征.秦岭-昆仑造山带中环斑花岗岩的显著特征是都产在造山带中,与板块缝合带关系密切,时代从元古宙到古生代直到中生代都有发现,具多旋回性.它们出现在每一个大的造山旋回晚期,即向另一个构造旋回的转折期,这在世界造山带中是十分罕见的,反映出世界上造山带与稳定区元古宙和显生宙的地幔与地壳状态是不一样的,有着不同的构造演化历史和动力学过程,表明秦岭-昆仑地区的环斑花岗岩是一种有别于元古宙稳定区的造山型环斑花岗岩.     

Magma mixing,the petrogenetic link between anorthositic suites and rapakivi granites, Åland,SW Finland

Summary The Åland, rapakivi batholith consists of several granites that differ texturally and mineralogically from quartz-porphyritic varieties to rapakivi varieties with K-feldspar ovoids (wiborgites and pyterlites) and aplitic granites. Closely associated with the batholith there is a mafc magmatic series of dolerite dykes, norites, anorthosites and monzodiorites.The earliest major intrusive phase of the Åland, rapakivi batholith consists of quartzporphyritic hornblende rapakivi. This rock contains small amoeboidal mafc enclaves, labradorite megacrysts, quartz ocelli, amphibole-mantled xenoliths and irregular clots of granophyric granite. These disequilibrium features are products of mixing between basaltic and granitic magmas. Geochemical modelling indicates that the quartzporphyritic hornblende rapakivi is a mixture of 15% hi-Fe monzodiorite (mafic endmember) and 85% quartz-feldspar porphyry (felsic end-member). The monzodiorite is derived from a norite-anorthosite-monzodiorite series. The quartz-feldspar porphyry is produced by partial melting of the country rock caused by intrusions of hot basic magma.Structural, textural and geochemical features suggest that magma mixing was an important petrogenetic process in the formation of the earliest rapakivi granite intrusions in the Åland, rapakivi batholith. Petrographic evidence of magma mixing can also be found in the major intrusion of the batholith, the wiborgite rapakivi granites. Chemically the mixing is difficult to specify in these rocks because of a high proportion of felsic component. Zircon and apatite fractionation trends, however, indicate that the wiborgite rapakivis also contain components from a mixed source.

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Magmamixing, die petrogenetische Verbindung zwischen Anorthositen und RapakiviGraniten, Åland, SW Finnland

Zusammenfassung Der Rapakivi Batholit von Åland besteht aus verschiedenen Graniten, die in ihrer Textur und Zusammensetzung das Feld von quarzporphyritischen über Rapakivigranite mit K-Feldspat-Ovoiden (Wiborgite und Pyterlite) und aplitischen Graniten abdecken. Eine mafische magmatische Serie von Dolerit-Gängen, Noriten, Anorthositen und Monzodioriten ist mit diesen Batholiten eng verbunden.Die erste größere Intrusivphase des Åland, Rapakivi Batholiten besteht aus quarzporphyritischem Hornblende Rapakivi. Dieses Gestein enhält kleine Amöboide, mafische Enklaven, Labradorit Megakristalle, Quarzocelli, Xenolithe mit Amphibolrändern und unregelmäßige Aggregate von granophyrischem Granit. Diese Produkte von Ungleichgewichts-Bedingungen gehen auf die Mischung zwischen basaltischen und granitischen Magmen zurück. Geochemische Modelle zeigen, daß der quarzporphyritische Hornblende-Rapakivi eine Mischung von 15%. eisenreichen Monzodiorit (mafisches Endglied) und 85% Quarz-Feldspatporphyr (felsisches Endglied) ist. Der Monzodiorit stammt von einer Norit-Anorthosit-Monzodiorit Serie. Der QuarzFeldspat-Porphyr entstand durch teilweise Aufschmelzung des Nebengesteines, die durch Intrusionen heißen basischen Magmas verursacht wurden.Strukturelle, texturelle und geochemische Daten zeigen, daß Magmamischung ein wichtiger petrogenetischer Prozeß der Bildung der frühesten Rapakivi-Granit-Intrusionen im Åland, Batholith waren. Petrographische Hinweise auf Magmamischung können auch in der größten Intrusion des Batholiths, dem Wiborg Rapakivi Granit, gefunden werden. Wegen des hohen Anteils felsischer Komponenten ist es schwierig, das Magmamixing in diesen Gesteinen chemisch zu quantifizieren. Zirkon- und Apatitfraktionierungs-Trends weisen jedoch darauf hin, daß auch die WiborgitRapakivis Komponenten aus einer gemischten Quelle enthalten.

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Geochemistry and Origin of Early Proterozoic Dongargarh Rapakivi Granite Complex, Central India - An Example for Magma Mixing and Differentiation

Early Proterozoic Dongargarh granite complex of Central India, intruding the tonalitic to granodioritic Amgaon gneisses and the Nandgaon Group bimodal volcanic suite, comprises three different textural and compositional types, viz., porphyritic granodiorite (PG), coarse equigranular granite (EG) and microgranite (MG). Synplutonic mafic dykes are common in the granite complex. The PG is characterised by rapakivi texture and the EG is the dominant facies and exhibits sporadically developed rapakivi texture. Microgranular enclaves are common in the EG while they are rare in PG. Major and trace element geochemistry of PG shows marked I- type and some occasional A-type granite characters unusual for a rapakivi granite while the EG shows A-type granite signatures. The field, petrographic, chemical and isotopic data of these granites suggest their derivation by mixing of mantle derived basic magma with a crustal-derived partly crystalline granitic magma. Episodic mafic magma underplating caused the anatexis of the Archaean lower continental crust in a continental margin tectonic setting resulting first in the formation of the I-type granodiorite followed by A-type granite. The I-type granodiorite is mixed with the basic magma (synplutonic dykes) while the EG is formed by mingling of A- type granite magma and the intruding basic magma.     

鹰峰环斑花岗岩地球化学特征及其构造意义

柴达木北缘鹰峰环斑花岗岩出露于柴达木地块与南祁连地体之间的柴北缘造山带,是我国发现的又一元古宙环斑花岗岩体.初步研究表明,鹰峰环斑花岗岩是具环斑结构和A-型花岗岩特征的典型的元古宙环斑花岗岩体,且属于A1亚型,岩浆组合具双峰式特征.环斑结构主要由几个钾长石斑晶颗粒形成聚斑,中心有一斜长石内核,斑晶表面具不均匀高岭土化,条纹构造明显且有规律,基质由细粒-微粒的石英组成,有明显重结晶及定向构造; 岩石化学组成以高钾为特征,A/ NKC < 1,A/NK > 1,属准铝质; 微量元素组成上富集Ba、U、Th、Ce、Hf、Sm,亏损Sr、Ta、Nb、Zr、Y,Rb/Sr (0.17~0.6)和Rb/Ba (0.03~0.24) 很低,岩石分异演化程度不高; 稀土元素: REE、Ce、Zr含量高,Ga含量高达25×10-6以上,远远高出其他类型花岗岩,但Eu (0.75~4.3) ×10-6轻度亏损,属轻稀土富集型.通过对微量元素和稀土元素的地球化学行为分析,鹰峰环斑花岗岩是发生在板内的一种岩浆作用,是下地壳的麻粒岩受底侵或拆沉作用地幔上涌影响,发生部分熔融,然后经过分异演化形成了碱性的“干”岩浆,并在后碰撞的区域拉伸构造环境下侵位.同时伴随温度的降低,钠质的斜长石从钾长石中出溶,并迁移到钾长石的边沿,形成了具环斑结构的A1型花岗岩.      

Microstructural evidence for magma confluence and reusage of magma pathways: implications for magma hybridization,Karakoram Shear Zone in NW India

In the Karakoram Shear Zone, Ladakh, NW India, Miocene leucogranitic dykes form an extensive, varied and complex network, linking an anatectic terrane exposed in the Pangong Range, with leucogranites of the Karakoram Batholith. Mineral paragenesis of the heterogeneous anatectic source rocks suggests melting has resulted from water influx into rocks at upper amphibolite facies conditions, and microstructures suggest anatexis was contemporaneous with shearing. The network is characterized by continuous and interconnected dykes, with only rare cross‐cutting relationships, forming swarms and chaotic injection complexes where magmatic rocks cover up to 50% of the outcrop area. Despite this volume of magma, the system did not lose continuity, suggesting that it did not flow en masse and that the magma network was not all liquid simultaneously. Leucogranites in this network, including leucosomes in migmatites, carry an isotopic signature intermediate between the two main anatectic rocks in the source, suggesting efficient homogenization of the magmatic products. Here, we describe a number of microscopic features of these magmatic rocks which suggests that several pulses of magma used the same pathways giving rise to textural and chemical disequilibrium features. These include: (i) narrow, tortuous corridors of fine‐grained minerals cutting across or lining the boundaries of larger grains, interpreted to be remnants of magma‐filled cracks cutting across a pre‐existing magmatic rock; (ii) corrosion of early formed grains at the contact with fine‐grained material; (iii) compositional zoning of early formed plagioclase and K‐feldspar grains and quartz overgrowths documented by cathodoluminescence imaging; (iv) incipient development of rapakivi and anti‐rapakivi textures, and (iv) different crystallographic preferred orientation of early formed quartz and fine‐grained quartz. Mapping of the fine‐grained corridors interpreted to represent late melt channels reveal an interlinked network broadly following the S‐C fabric defined by pre‐existing magmatic grains. We conclude that early formed dykes provided a pathway exploited intermittently or continuously by new magma batches. New influxes of magma opened narrow channels and migrated through a microscopic network following predominantly grain boundaries along an S‐C fabric related to syn‐magmatic shearing. A mixed isotopic signature resulted not from the mixing of magmas, but from the micro‐scale interaction between new magma batches and previously crystallized magmatic rocks, through local equilibration.     

北秦岭老君山环斑花岗岩的成因及大地构造意义

老君山环斑花岗岩分布于北秦岭造山带中，是沙河湾、朱厂沟脑、秦岭梁北秦岭环斑花岗岩带的一部分，以特殊的环斑结构，富含基性暗色微粒包体为特征，通过对其地质、岩石、地化资料研究，结合区域大地构造环境，认为老君山环斑花岗岩，具有岩浆混合成因类型，为造山后伸展环境的产物，标志着印支期末秦岭地区俯冲碰撞的板块构造体制已经结束，转入板内构造演化阶段。     

花岗岩暗色微粒包体特征及其研究方向

通过调研近年来国内外学者对于花岗岩类中暗色微粒包体的研究成果,总结了其野外地质、岩相学、地球化学和同位素等特征以及成因研究中的主要问题。暗色微粒包体(MME)广泛分布于I型花岗岩中,一般呈随机分布,形态多样,但以塑性特征为主;一般认为是岩浆混合成因,其原始物源是玄武质岩浆,具典型的火成岩结构,发育针状磷灰石、环带结构和筛状结构的斜长石;相对于寄主岩石,暗色微粒包体富Fe,Mg,贫Si,Na,其锆石U-Pb年龄在误差范围内与寄主岩石年龄一致等,反映了壳幔源岩浆的混合事件。暗色微粒包体与岩浆动力学行为、矿化关系及区域地质演化等方面值得进一步研究、探索。     

滇西富碱斑岩型矿床岩体和矿脉同位素地球化学研究

选取马厂箐铜钼金矿、金厂箐金矿、北衙铅金矿和姚安铅银金矿四个典型的富碱斑岩型多金属矿床，对岩体和矿脉的铅、硅、氢、氧、硫、碳及氦、氩同位素分析。结果表明，富碱岩浆和富硅成矿流体的最初和主要铅源均来自地幔，但混染了部分地壳或地层铅；富碱岩浆起源于地幔交代作用形成的富集地幔源区，而富硅成矿流体则具有原始地幔流体性质，前者的硅同位素组成表现为经历强烈动力分馏的高正值；后者则为几乎未经动力分馏的低负值。综合研究表明，该类矿床的成矿作用是在富碱岩浆的成岩过程中，伴随富硅成矿流体对岩体和地层围岩的(自)交代蚀变作用，并与岩石一定程度混染而实现的。因此，富硅成矿流体作用实质上是地幔流体交代作用在地壳内成矿作用中的延续。