西昆仑山A型花岗岩带的发现及其地球动力学意义

西昆仑山发育一条醒目的Ａ型花岗岩带,空间上与库地幔台展布范围相一致;它形成于印支晚期,与海西晚期Ⅰ型花岗岩共生;岩石相对富碱、ＬＲＥＥ、Ｙ、Ｎｂ、Ｚｒ,贫Ａ１、Ｍｇ、Ｃａ、Ｂａ、Ｓｒ及过渡元素,又以ＳｉＯ２含量范围宽（６６％～７７％）为其显著特色,与澳大利亚东部ＣｈａｅｌｕｎｄｉＡ型花岗岩极为相似。研究表明,花岗岩属Ａ１型,形成于造山晚期相当稳定的拉张环境,是在岩石圈拆沉过程中侵位的。     

Nature and origin of A-type granites with particular reference to southeastern Australia

In the Lachlan Fold Belt of southeastern Australia, Upper Devonian A-type granite suites were emplaced after the Lower Devonian I-type granites of the Bega Batholith. Individual plutons of two A-type suites are homogeneous and the granites are characterized by late interstitial annite. Chemically they are distinguished from I-type granites with similar SiO₂ contents of the Bega Batholith, by higher abundances of large highly charged cations such as Nb, Ga, Y, and the REE and lower Al, Mg and Ca: high Ga/Al is diagnostic. These A-type suites are metaluminous, but peralkaline and peraluminous A-type granites also occur in Australia and elsewhere. Partial melting of felsic granulite is the preferred genetic model. This source rock is the residue remaining in the lower crust after production of a previous granite. High temperature, vapour-absent melting of the granulitic source generates a low viscosity, relatively anhydrous melt containing F and possibly Cl. The framework structure of this melt is considerably distorted by the presence of these dissolved halides allowing the large highly charged cations to form stable high co-ordination structures. The high concentration of Zr and probably other elements such as the REE in peralkaline or near peralkaline A-type melts is a result of the counter ion effect where excess alkali cations stabilize structures in the melt such as alkali-zircono-silicates. The melt structure determines the trace element composition of the granite. Separation of a fluid phase from an A-type magma results in destabilization of co-ordination complexes and in the formation of rare-metal deposits commonly associated with fluorite. At this stage the role of Cl in metal transport is considered more important than F.     

新疆乌伦古河碱性花岗岩的地球化学及其构造意义

在新疆北部准噶尔板块与阿尔泰造山带的缝合带即阿尔曼泰-扎河坝蛇绿混杂岩带附近,沿乌伦古河南岸分布一条碱性花岗岩带。它们形成的时代为292-309Ma,是阿尔泰地区海西期继同碰撞s型花岗岩类、碰撞后抬升Ⅰ型花岗岩类之后的最后一次岩浆活动的产物。这些碱性花岗岩以出现霓石、钠铁闪石、高硅、高碱、低钙、低镁、富集高场强元素为特征,属于典型的A型花岗岩。碱性花岗岩是海西期岩浆旋回的最后产物,活动时间很短暂,在空间上与蛇绿岩带伴生,为后造山A型碱性花岗岩(PA型),是阿尔泰海西期造山运动结束的重要标志。     

Two different magma series imply a Palaeogene tectonic transition from contraction to extension in the SE Korean Peninsula

Late Cretaceous–early Tertiary granites in the Gyeongsang Basin have distinctly different bulk-rock compositions. Calc-alkaline I-type metaluminous granites display petrographic features implying magma mixing, whereas A-type granites are hypersolvus and peralkaline. I-type plutons mainly consist of enclave-rich granodiorites and enclave-poor porphyritic granites typified by abundant plagioclase phenocrysts; these granitoids contain various mafic clots and magmatic/microgranular enclaves (MMEs). A-type bodies are perthitic alkali-feldspar granites characterized by interstitial annite + riebeckite-arfvedsonite. New SHRIMP-RG zircon U–Pb age dating of an I-type enclave-poor porphyritic granite and an A-type alkali-feldspar granite yielded ages of 65.7 ± 0.7 and 53.9 ± 0.3 million years, respectively. Based on prior geochronologic data and these contrasting ages of granitic magma genesis, SE Korea may have evolved tectonically from latest Cretaceous compression to late Palaeocene extension (i.e. orogenic collapse). The later part of the 66–54 Ma magmatic gap apparently includes the time of tectonic inversion in the SE Korean Peninsula, a far-field effect of the collision of the Indian subcontinent with Eurasia. This process is also reflected in the 69–52 Ma NNE-trending Eurasian apparent polar wandering path.     

华北东部早白垩世A型花岗岩与克拉通破坏

A型花岗岩是非造山的、无水的碱性花岗岩, 具有独特的矿物学、岩石学和地球化学特征, 形成于造山后、板内非造山或者地幔热柱等伸展动力学背景, 蕴涵着大陆地壳生长、岩石圈演化及区域构造发展等大陆动力学的重要信息.在华北东部广泛分布着一期中生代A型花岗岩及伴生的碱性岩, 结合前人的研究成果以及笔者近年来的研究发现: 它们主要侵位于早白垩世(130~110Ma), 来源于上地壳、下地壳和地幔等多元源区, 是不同成分的岩浆经过分离结晶、岩浆混合作用形成; 综合区域地球动力学研究和A型花岗岩本身的地球化学特征, 认为华北东部早白垩世A型花岗岩形成于地壳伸展背景之下, 是岩石圈减薄和克拉通破坏的浅部地质响应, 标志着华北东部岩石圈减薄和克拉通破坏作用的峰期.      

十杭带湘南—桂北段中生代A型花岗岩带成岩成矿特征及成因讨论

十杭带是华南内陆一条重要的北北东向、具有高εNd (t )值和低t DM值的花岗岩带,该带在湘南—桂北段的花岗质岩体（千里山、骑田岭、西山、金鸡岭、花山和姑婆山等）均形成于151~163 Ma间。但从西南往东北方向,形成时代有逐渐变年轻的趋势。这些岩体在地球化学组成上显示出较为相似的特征,岩石均富碱、高钾,富含Rb,Th,U等大离子亲石元素（LILE）和REE,Nb,Ta,Zr,Hf等高场强元素（HFSE）。在地球化学图解上均落入A型花岗岩区域,因此该花岗岩带应属于一条A型花岗岩带。进一步划分,这些花岗岩应该属于A2亚类。这些花岗岩均具有较低的（87Sr/86Sr）i 值、较高的εNd (t )值和相对低的Nd模式年龄值,但从西南往东北方向,εNd (t )值具有逐渐降低的趋势。在这些花岗质岩体中暗色包体非常发育,岩石学和地球化学,特别是锆石的Hf同位素组成,指示这些花岗质岩石是通过壳-幔岩浆混合作用形成的,幔源岩浆端元来自亏损地幔,可能是软流圈地幔物质的直接参与。该A型花岗岩带可能形成于古太平洋板块俯冲引起的弧后或弧内拉张构造环境,软流圈地幔上涌及诱发的幔源岩浆沿超壳深断裂底侵,导致了强烈的壳幔岩浆混合作用,形成了该花岗岩带。该拉张事件从西南往东北方向进行,拉张强度由强变弱,混入花岗岩中的地幔物质也由多变少。该花岗岩带也是我国 一条重要的W-Sn多金属成矿带。研究表明,这些花岗岩均属于富Sn花岗岩,但Sn在这些花岗岩中的富集机制与传统的结晶分异富集的方式不同。该区锡矿化类型十分丰富,除了存在传统的岩浆热液演化成矿外,还存在新类型的绿泥石化花岗岩锡矿化,丰富了A型花岗岩的成矿理论。     

The Late Triassic Dengfuxian A-type granite,Hunan Province: age,petrogenesis, and implications for understanding the late Indosinian tectonic transition in South China

The Triassic (Indosinian) granites in the South China Block (SCB) have important tectonic significance for understanding the evolution of Eastern Asia. The Dengfuxian biotite granite in eastern Hunan Province, China, reported in this article, was recognized as Late Triassic (late Indosinian) weakly peraluminous A-type granite with a zircon laser ablation inductively coupled plasma mass spectrometry U–Pb age of 225.7 ± 1.6 Ma. It is enriched in F, Cs, Rb, Th, high field strength elements, and rare earth elements (REEs) and depleted in Ba, Sr, P, Ti, Nb, and Ta, with high Ga/Al ratios and zircon saturation temperatures. The Dengfuxian biotite granite shows high initial Sr isotope values (0.715932 to 0.716499) and negative ?_Nd(t) (?10.46 to ?9.67) and ?_Hf(t) (?9.92 to ?6.29) values, corresponding to the Nd model ages of 1.79 to 1.85 Ga and the Hf model ages of 1.65 to 1.88 Ga. It is proposed that the Dengfuxian biotite granite was derived from high-temperature partial melting of the Palaeoproterozoic lower crust undergoing granulitization. Some Late Triassic A-type granites were recently identified in the SCB with the ages between 202 and 232 Ma. These A-type granites have the same geochemical characteristics and petrogenesis as Dengfuxian A-type granite, and show A₂-subtype granite affinity. The Late Triassic A-type granite formed a NE-trending granite belt, which is consistent with the main NE-trending faults in the SCB. The formation of these A-type granites was in response to the subduction of the palaeo-Pacific plate underneath the SCB, and indicates an extensional tectonic environment in the SCB. Combined with previous studies on tectonic evolution, we suggest that there may be a tectonic transition inside the SCB from compression to extension at least from 225 to 230 Ma.     

Petrology,geochemistry and genesis of Kuiqi granite batholith

The Kuiqi granite batholith outcrops in the vicinity of Fuzhou City, Fujian Province and constitutes one of the typical alkali granitic complexes in the “Belt of Miarolitic Granites” extending along the southeast coast of China. The complex is believed to have been emplaced at higher levels of the crust in a tensional fault environment. Petrographically it is composed mainly of aegirine-arfvedsonite granites with early biotite granites scattered. Miarolitic structure and granophyric texture are commonly observed. The Rb-Sr isochron age of the complex is 107.65 m.y. Both petrological and petrochemical studies show that the Kuiqi granite is of A-type. Data on chemical composition, REE pattern and transition elements reveal that there is a close genetic connection between granites and associated volcanic rocks. Thus, syntexistype (I-type) granite, A-type granite and volcanic rocks form a cogenetic “trinity”, in which the A-type granite is usually the latest member of the volcanic-intrusive series.     

皖南及邻区燕山期A2型花岗岩地球化学特征及岩石成因

皖南及邻区早白垩世中—晚期酸性岩浆岩产于扬子陆块江南古隆起东段,岩体类型为花岗岩、碱长花岗岩及钾长花岗岩。岩体含有丰富的锆石、富F的萤石及富含稀土的磷钇矿、独居石、褐帘石等矿物。主量元素具较高含量的SiO2和K2O,较低含量的TiO2、MgO、CaO,高(Na2O+K2O)/Al2O3值,高FeOT/MgO比;富集REE(Eu亏损),HREE亏损不严重,稀土配分模式表现为海鸥型;明显富集Zr、Nb、Rb、Ta、Y、Yb,显著亏损Cr、Co、Ni、V、Ba、Sr。地化特征分析认为早白垩世中—晚期花岗岩为A2型花岗岩,产生于造山后的伸展环境,是正常安山质地壳在皖南印支期加厚地壳熔融结束之后继续受地幔物质底侵部分熔融所形成。     

西藏班公湖-怒江缝合带中段碰撞后A型花岗岩的时代及其对洋盆闭合时间的约束

近年来地质调查在班公湖-怒江缝合带中段发现了一批A型花岗岩,岩体呈面积不大(＜1 km2)的岩株产出,岩性上分为钾长花岗岩和花岗闪长斑岩两种,侵入白垩系地层中.岩石化学上这些A型花岗岩相对富硅,SiO2含量在68.62％～75.36％之间,全碱含量(K2O+Na2O=8.03％ ～ 9.37％)和全铁含量(FeO(T)...     

龙王(石童)A型花岗岩地质矿化特征

东秦岭北侧的华北古陆块南缘,发育一条碱性岩和碱性花岗岩带。龙王碴碱性花岗岩是该带中的一个典型的A型花岗岩体,岩石富含K、Na,缺Mg、Ca,多Fe少Al和水,含有碱性暗色矿物和很高的F及稀土元素,形成于非造山环境,属板内花岗岩。成岩时代为晋宁期(1035Ma,Rb-Sr)。龙王(石童)A型花岗岩的发现和厘定,证明华北地台南缘在中上元古代存在一个拉张的裂谷系。     

三江地区义敦岛弧碰撞造山过程：花岗岩记录

义敦岛弧碰撞造山带是特提斯－喜马拉雅巨型造山带中的一个复合造山带。本文利用义敦岛弧碰撞造山带29个花岗岩体的43件同位素测年数据，结合岩石地球化学特征，建立了造山带花岗岩的时间坐标。初步识别出4套不同成因类型的花岗岩，即印支期弧花岗岩、燕山早期同碰撞花岗岩、燕山晚期A型花岗岩和喜马拉雅期花岗岩。据此，再造了造山带的形成过程与演化历史：印支期的大规模俯冲造山作用（238－210Ma)，形成义敦火山岩浆弧；大约自206Ma始，发生弧－陆碰撞，伴随岛弧地壳挤压收缩和剪切变形，发育同碰撞花岗岩；进入燕山晚期（138－73Ma)，岛弧碰撞造山带发生造山后伸展作用，形成A型花岗岩带；喜马拉雅期发生陆内造山作用（65－15Ma)，岛弧碰撞造山带出现逆冲－推覆和大规模走滑平移，伴随喜马拉雅期花岗岩的侵位和拉分盆地的形成。     

黑龙江省五道岭地区花岗斑岩地球化学特征及地质意义

五道岭钼矿床是伊春—延寿成矿带上最南部的矽卡岩型矿床。本次工作通过调研矿床寄主岩石边缘的花岗斑岩发现,花岗斑岩与赋矿正长花岗岩不仅形成时代一致,还存在岩石地球化学的相似性:花岗斑岩的锆石U-Pb年代学显示其形成时代为(194.1±2.0)Ma,寄主岩石正长花岗岩形成时代为(193.9±1.3)Ma;花岗斑岩为I型向A型花岗岩过渡的岩石类型,更趋近于A型花岗岩,正长花岗岩属于典型的A型花岗岩,且两者均为高Si、富K-Na、富Al的高钾钙碱性-弱碱性、准铝-过铝质的岩石,具有富集大离子亲石元素Rb、K和轻稀土元素,亏损高场强元素Nb、Ta、P、Ti等特点,两者微量和稀土元素分布趋势一致,显示它们可能是同源岩浆的产物。花岗斑岩的初始Sr比值~(87)Sr/~(86)Sr为0.723 123,结合区域地质演化特征认为,五道岭花岗质岩体可能形成于古太平洋板块俯冲挤压后期的伸展环境,矽卡岩型钼矿床的成矿作用或许与花岗斑岩的侵入密切相关,暗示区域上存在这期花岗斑岩成矿的可能性。     

A型花岗岩研究进展与问题讨论

自"A型花岗岩"的概念提出以来,经过30年的研究,有关"A型花岗岩"的岩石类型、构造环境、岩浆来源及成因等的定义与认识都发生了很大变化,目前"A型花岗岩"有扩大化现象,不少所谓的"A型花岗岩"已与A型花岗岩的原始定义相去甚远,并可能有逐渐发展为"拉张环境下形成的花岗岩都属A型花岗岩"的趋势。笔者通过资料调研和对比研究,认为"A型花岗岩"的确定需回归其原始定义,注意强调其"3A"特征,在此基础上才能正确探讨岩浆成因及其构造指示环境。     

新疆巴里坤县大加山一带碱性花岗岩的特征及构造环境探讨

大加山一带的碱性花岗岩按侵入先后可分为碱长花岗岩单元、钠闪石碱性花岗岩单元、霓石钠门石碱性花岗岩单元，由它们构成大加山超单元。这些岩石大都含碱性暗色矿物，从矿物组合看具贫水特征，岩石化学方面显示高硅、高碱、贫铝、镁、钙等特征；微量元素显示钾、铷、钍富集，锶、钡等强烈亏损特点；稀土元素总量较高，轻稀土较重稀土富集，并具有强的负铕异常。就位机制为断裂扩张并具顶蚀型被动定位类型，同源岩浆演化具反序列演化特点。上述特征和区域构造环境分析表明，大加山一带碱性花岗岩为非造山环境下形成的Ａ型花岗岩。     

A型花岗岩的研究进展及意义

A型花岗岩主要形成于伸展的构造背景中,是构造环境识别的重要岩石学标志之一。由于形成于特殊的构造背景和重要的地球动力学意义,A型花岗岩的研究一直得到广泛的关注,但是仍旧有许多问题(如命名、分类和成因等)在争论之中。本文从下面几个方面对A型花岗岩的研究现状进行了较系统的总结:(1)A型花岗岩的概念及特征;(2)A型花岗岩与高分异I、S型花岗岩的区别;(3)A型花岗岩的物质来源及成因模式;(4)A型花岗岩的实验岩石学成果;(5)A型花岗岩的分类;(6)A型花岗岩的构造背景及动力学意义。A型花岗岩在形成过程中斜长石、斜方辉石可能为主要的残留或分离结晶矿物相。除了传统的A1(非造山)、A2(后碰撞)分类外,"还原型"和"氧化型"的分类方案最近也受到广泛关注。     

Oxidized, magnetite-series, rapakivi-type granites of Carajás, Brazil: Implications for classification and petrogenesis of A-type granites

The varying geochemical and petrogenetic nature of A-type granites is a controversial issue. The oxidized, magnetite-series A-type granites, defined by Anderson and Bender [Anderson, J.L., Bender, E.E., 1989. Nature and origin of Proterozoic A-type granitic magmatism in the southwestern United States of America. Lithos 23, 19–52.], are the most problematic as they do not strictly follow the original definition of A-type granites, and approach calc-alkaline and I-type granites in some aspects. The oxidized Jamon suite A-type granites of the Carajás province of the Amazonian craton are compared with the magnetite-series granites of Laurentia, and other representative A-type granites, including Finnish rapakivi and Lachlan Fold Belt A-type granites, as well as with calc-alkaline, I-type orogenic granites. The geochemistry and petrogenesis of different groups of A-types granites are discussed with an emphasis on oxidized A-type granites in order to define their geochemical signatures and to clarify the processes involved in their petrogenesis. Oxidized A-type granites are clearly distinguished from calc-alkaline Cordilleran granites not only regarding trace element composition, as previously demonstrated, but also in their major element geochemistry. Oxidized A-type granites have high whole-rock FeO_t/(FeO_t + MgO), TiO₂/MgO, and K₂O/Na₂O and low Al₂O₃ and CaO compared to calc-alkaline granites. The contrast of Al₂O₃ contents in these two granite groups is remarkable. The CaO/(FeO_t + MgO + TiO₂) vs. CaO + Al₂O₃ and CaO/(FeO_t + MgO + TiO₂) vs. Al₂O₃ diagrams are proposed to distinguish A-type and calc-alkaline granites. Whole-rock FeO_t/(FeO_t + MgO) and the FeO_t/(FeO_t + MgO) vs. Al₂O₃ and FeO_t/(FeO_t + MgO) vs. Al₂O₃/(K₂O/Na₂O) diagrams are suggested for discrimination of oxidized and reduced A-type granites. Experimental data indicate that, besides pressure, the nature of A-type granites is dependent of ƒO₂ conditions and the water content of magma sources. Oxidized A-type magmas are considered to be derived from melts with appreciable water contents (≥ 4 wt.%), originating from lower crustal quartz-feldspathic igneous sources under oxidizing conditions, and which had clinopyroxene as an important residual phase. Reduced A-type granites may be derived from quartz-feldspathic igneous sources with a metasedimentary component or, alternatively, from differentiated tholeiitic sources. The imprint of the different magma sources is largely responsible for the geochemical and petrological contrasts between distinct A-type granite groups. Assuming conditions near the NNO buffer as a minimum for oxidized granites, magnetite-bearing granites formed near FMQ buffer conditions are not stricto sensu oxidized granites and a correspondence between oxidized and reduced A-type granites and, respectively, magnetite-series and ilmenite-series granites is not always observed.     

福建太姥山地区和鼓山地区A型花岗岩对比及其地球动力学意义

太姥山和鼓山位于福建东南沿海地带。岩石学和岩相学研究表明太姥山地区和鼓山地区花岗岩分属铝质A型花岗岩和碱性A型花岗岩。锆石LA-ICP-MS U-Pb同位素定年结果表明,两地区花岗岩成岩年龄分别为(96.6±1.6)Ma(MSWD=0.65)和(99.4±2.3)Ma(MSWD=0.49),成岩时代均属晚白垩世早期。结合中国东部沿海两类A型花岗岩,讨论了它们在岩石学、岩相学、地球化学及其判别图解上的区别。总体上认为,碱性A型花岗岩在AKI值、TFeO/MgO比值、104×Ga/Al以及(Zr+Nb+Ce+Y)值上均大于同区域的铝质A型花岗岩,但上述化学指标的数值也存在一定范围的重叠;且传统A型花岗岩判别图解不完全适用于强分异的铝质A型花岗岩。地球化学特征表明,两地区A型花岗岩应具有相似的源区,即岩浆起源于地壳物质熔融,同时成岩过程有一定的地幔物质参与。但鼓山地区碱性A型花岗岩较太姥山地区铝质A型花岗岩有更多地幔物质的加入,导致前者显示出部分幔源岩浆起源的特征。结合地球化学、野外地质、区域背景及年代学综合判定,两地区花岗岩成因与古太平洋板块对欧亚板块的俯冲角度密切相关,均属于弧后拉伸体制之下的构造环境。     

A型花岗岩的实质是什么？

A型花岗岩是富碱、贫水的花岗岩类,地球化学上以贫Al、Sr、Eu、Ba、Ti、P为特征,形成于低压高温条件下,对源岩没有选择。A型花岗岩的实质为:在低压下部分熔融形成的花岗岩类,大多产于地壳伸展减薄的构造背景中。     

The Yenshanian—type Twin Granite Belts in Intracontinental Compression—subduction Environments in the Northern Part of East Qinlin Area

Calc-alkaline granites (excluding A-and M-type) could be divided into two petrogenic series,I,e,the syntexis series and the transformation series according to their genetic mechanisms.In the light of this classification we found that granites of these two series often aligne in paired zones parallel to contemporaneous B-type or intracontinental compression-subduction zones within ascended slabs,re-sulting in a regular zonal pattern together with subduction zones.Thus,they are defined as twin granite belts.According to the spatial relations between the granite belts and the subduction zones,the twin granite belts could be classified as A, AB and B-type .The zonation of granites of the two series in the northern part of the East Qinlin area could be cited as a typical example of A-type twin granite belts related to the Yenshanian intracontinenta compression-subduction movement in the area.In this paper the tectonic settings and petrogenic features of the twin granites belts in East Qinlin are systematically described,and a tectonic model for granitic magma genesis in intracontinental compression-subduction environments has been proposed.In this model the forma-tion of A-type twin granite belts is closely connected with tectonic movements in terms of the prince-ple,rule and dynamics of material differentiation in the lithosphere.