香草坪花岗岩体年代学和地球化学特征

香草坪岩体主要岩性为中粗粒斑状黑云母花岗岩,SHRIMP锆石U-Pb法年龄为211±2Ma,属于印支期岩浆作用产物。岩石地球化学特征研究表明,其ACNK,微量元素模式图曲线形态总体向右倾,以及轻稀土富集、Eu明显亏损的稀土配分模式曲线特征,与华南S型花岗岩的地球化学特征相似。该岩体高(87Sr/86Sr)i和低εNd(t)的特点,表明其可能是前寒武系中等成熟度的基底岩石经部分熔融形成的。该区基底岩石较高的铀含量,可为香草坪岩体提供充足的铀元素,形成铀元素的初始富集。     

Strongly peraluminous granites of Mesozoic in Eastern Nanling Range,southern China: Petrogenesis and implications for tectonics

The strongly peraluminous granites (SPGs) of Eastern Nanling Range (ENR) are a characteristic of all bearing highly aluminous minerals, such as muscovite±AI-rich biotite±tourmaline±garnet, and lack of cordierite. In respect of petrography, geochemistry, Nd isotope, and single grain zircon U-Pb dating, the representative granite bodies of them are studied. The research shows that these granites were emplaced in two stages, namely 228-225 Ma BP and J2-3 159-156 Ma BP, belonging to Indosinian and early Yanshanian periods, respectively, and they have low εNd(t) values (-10.6--11.1), high A/CNK, Rb/Sr ratios and tDM values (1887-1817 Ma), and REE's tetrad effect (TE1,3=1.13-1.34). In comparison with related geology, petrology and chronology of granites in adjacent regions, it is suggested that Indosinian SPGs of ENR formed in the circumstance of post-collisional extension 20 Ma after the major collision of Indosinian Movement (258-243 Ma BP) in Indo-China Peninsula, and early Yanshanian SPGs formed in the     

磷对过铝质岩浆液相线温度影响的实验研究

以宜春414岩体中的钠长花岗岩作为实验初始物,利用"RQV-快速内冷淬火"高温高压装置实验研究了100MPa压力、含5%H2O条件下,P对过铝质花岗岩液相线温度的影响.实验结果表明,碱性长石是最早结晶的矿物;随着体系中P2O5含量从0.27%增加到7.71%,液相线温度从最初的810℃降低到740℃,表明P有效地降低了过铝质岩浆体系的液相线温度.在过铝质岩浆体系中,P5+与Al3+的结合形成AlPO4,降低了熔体中碱性长石组分的活度,很可能是液相线温度降低的机制.     

中阿尔泰造山带北缘早泥盆世构造环境探讨:来自托普色克他乌地区过铝质花岗岩年代学和地球化学的制约

中阿尔泰造山带北缘早泥盆世花岗岩的年代学和地球化学研究,对探讨该地区早泥盆世构造格架和演化过程具有重要意义。针对侵入于喀纳斯群哲里开特组的托普色克他乌花岗闪长岩体进行LA-ICP-MS锆石U-Pb定年,获得其^( 206)Pb/²³⁸U加权平均年龄为404 Ma±3.2 Ma(MSWD=0.32),为早泥盆世岩浆活动的产物。全岩地球化学分析表明,岩石具有高硅(w_SiO2     

西秦岭北缘天水地区新元古代花岗质片麻岩地球化学特征及其形成环境

西秦岭北缘新元古代花岗质片麻岩位于天水地区分隔北秦岭造山带和北祁连构造带的新阳-元龙韧性剪切带中。花岗质片麻岩具高Si、高Al的特征,属高钾钙碱性系列,A/CNK在1.104～1.389之间,为硅、铝过饱和类型,属典型的强过铝质S型花岗质岩石。轻、重稀土元素分馏较强,具中等负Eu异常。岩石富集大离子亲石元素（Cs、Rb、Ba、Th、U、K、La等）,强烈亏损高场强元素（Nb、Ta、Ti、Hf等）,明显的Ba、P、Sr负异常,相对富集Zr。该花岗质岩石是一种典型的壳源成因类型,主要为上地壳中以成熟度较低、含泥质成分较高的杂砂岩、岩屑杂砂岩为原岩的古元古界秦岭岩群中含水矿物相脱水部分熔融形成的,可能存在少量的分离结晶作用。该花岗质片麻岩具有同碰撞型花岗岩的特征,可能是北秦岭微地块与相邻地块在新元古代早期发生汇聚的产物,是Rodinia超大陆在西秦岭地区汇聚的响应。     

贵州梵净山白云母花岗岩锆石年代、铪同位素及对华南地壳生长的制约

贵州梵净山地区位于＂江南造山带＂西南段,出露地层为中新元古界梵净山群、青白口系板溪群、南华系及古生界地层。梵净山群已强烈褶皱,被青白口系板溪群角度不整合覆盖。浅色白云母花岗岩侵位于褶皱的梵净山群中;锆石原位LA-ICP-MS分析结果显示,其形成时代为（838.5±1.5）Ma。地球化学分析结果表明,其A/CNK值〉1....     

松潘造山带马尔康强过铝质花岗岩的成因及其构造意义

松潘造山带广泛出露印支期后碰撞型花岗岩类, 其中包括埃达克质花岗岩类、A型花岗岩和I型花岗岩, 但目前人们对该区印支期强过铝质花岗岩尚未有深入的研究.松潘造山带马尔康花岗岩属于强过铝质花岗岩(A/CNK=1.10~1.20), 其岩石类型主要为中粒二云母花岗岩和中细粒二云母花岗岩.利用LA-ICP-MS锆石U-Pb定年方法, 获得中粒二云母花岗岩的岩浆结晶年龄为208±2Ma, 中细粒二云母花岗岩的岩浆结晶年龄为200±2Ma.马尔康强过铝质花岗岩K₂O/Na₂O=1.13~1.75, 富Rb、Th和U, 贫Sr、Ba、Co和Ni等元素; 稀土元素组成上显示存在强到中等的负Eu异常(Eu/Eu*=0.15~0.65);全岩初始87Sr/86Sr比值(ISr) 为0.70712~0.71137, εNd (t) =-10.36~-8.43, 锆石εHf (t) =-11.8~-1.1.地球化学和Sr-Nd-Hf同位素组成一致表明, 它们的岩浆来自于地壳物质的部分熔融, 其中中粒二云母花岗岩的源岩类型主要为地壳中的泥质岩类, 而中细粒二云母花岗岩的源岩主要为地壳中的杂砂岩类.结合松潘带的地质背景、区域构造-岩浆事件及其岩浆岩的组合分析, 印支期岩石圈拆沉作用可以用来解释马尔康强过铝质花岗岩的形成机制.在松潘带, 印支期岩石圈拆沉作用导致软流圈物质上涌, 这不仅促使了加厚下地壳物质发生部分熔融, 如松潘带印支期埃达克质和I型花岗岩浆的形成, 而且还诱发了中地壳物质的部分熔融, 如马尔康强过铝质花岗岩的形成.这表明松潘带印支期岩石圈拆沉作用已使地壳不同层次发生部分熔融作用.      

Generation of Late Cretaceous silicic rocks in SE China: Age, major element and numerical simulation constraints

Rhyolite-dominating bimodal volcanic suites (rhyolite/basalt), mafic dikes and A-type granites distribute from N Zhejiang to S Fujian over 800 km in the Southeast Coast Magmatic Belt (SCMB) – the Late Yanshanian (LY) orogenic belt in SE China. Data of ⁴⁰Ar/³⁹Ar and K–Ar whole-rock ages and LA-ICPMS U–Pb zircon ages indicate that rhyolitic volcanism (101–72 Ma) is contemporaneous with the A-type granitic intrusions (100–90 Ma) and mafic dike injections (94–77 Ma). This time span is used to define the upper volcanic series in Zhejiang–Fujian areas. One striking feature of rhyolites in the SCMB is that many are strongly peraluminous (SP) and others, mostly restrict in Fujian, are peralkaline to mildly peraluminous (P-MP) and chemically resemble A-type granites. The SP character is unique among well-known large rhyolite provinces worldwide. Based on experimental works for a common thermal regime and inherited zircon age information, we suggest that SP and P-MP rhyolites represent low pressure melting of the felsic (quartzofeldspathic) granite (±metapelite) and the accompanied granodioritic, tonalitic and trondhjemitic member of the core complex assemblage, respectively, to account for the decreasing aluminosity. They could have also been contaminated by young igneous rocks, and ancient crust to a lesser degree, during ascent to the surface. Plate subduction and lithosphere extension processes, respectively, are numerically simulated for the magma generation of these rhyolites using the mafic underplating model. Results suggest that the most effective controlling factor to generate SP and associated P-MP (A-type) magmas during 95–80 Ma is thinning of the lithosphere thickness with a high exhumation rate. Under this circumstance, the core complex assemblage can be uplifted to lower level of the crust and match the constraint of experimental works.     

江西省武功山地区浒坑花岗岩的锆石U-Pb定年及元素地球化学特征

浒坑花岗岩侵入体位于武功山复式背斜东南翼,发育有大型的浒坑石英脉型钨矿床,其是武功山钨、铜、铋、钼多金属成矿带的重要组成部分.本文通过对浒坑白云母花岗岩精确的锆石LA-ICPMS U-Pb测年,测得其成岩时代为151.6±2.6Ma,属晚侏罗世,对应于华南中生代第一次花岗岩侵位事件(164～153Ma);其花岗岩岩浆的形成温度为676～695℃.通过浒坑花岗岩主微量元素结果的分析,认为浒坑白云母花岗岩属于高钾钙碱性系列,为准铝质-弱过铝质的分异S型花岗岩,其源岩为富粘土的泥质来源,形成于岩石圈伸展减薄环境.     

金川—过铝多阶段花岗岩体演化特征及其与成矿关系

可尔因岩体自前锋石英闪长岩-二长花岗岩-钾长花岗岩-二云母花岗岩-花岗伟晶岩,分布于同一复式背斜内,并具有时空的、多阶段的、连续系列演化特点。在岩石化学等方面是过铝、高碱质、富挥发组分F和稀有元素Li,Be等,并向晚阶段岩石富集。含矿岩体位于“岩浆树”顶端-二云母花岗岩-花岗伟晶岩带。伟晶岩围绕主岩体成群、带状分布。岩体成生于印支末期(206Ma)。