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   总被引：41，自引：0，他引：41  

蒋少涌  赵葵东  姜耀辉  戴宝章 《高校地质学报》2008,14(4):496-509

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。  相似文献   

安徽繁昌中生代侵入岩的特征和锆石SHRIMP测年   总被引：37，自引：0，他引：37  

楼亚儿  杜杨松 《地球化学》2006,35(4):359-366

安徽繁昌地区属于长江中下游铁、铜、硫、金成矿带的一部分。区内广泛发育燕山期侵入岩。侵入岩的岩性主要为黑云母石英二长岩至花岗岩,但以花岗岩为主。岩石富含钾长石,SiO2、K2O含量明显比铜陵地区中生代侵入岩的要高。锆石SHRIMP法测年表明繁昌板石岭黑云母石英二长岩的形成年龄为(125.3±2.9)Ma,滨江花岗岩的形成年龄为(124.3±2.5)Ma,铜陵侵入岩(鸡冠石花岗闪长岩、小铜官山石英闪长岩)的SHRIMP年龄分别为(135.5±4.4)Ma、(139.5±2.9)Ma,因而确定繁昌侵入岩的形成比铜陵岩体至少要晚十几百万年。岩石的全岩主元素以及微量和稀土元素分析结果表明,繁昌地区的板石岭岩体和浮山岩体为典型的A型花岗岩类,而滨江花岗岩体是岩浆演化到最晚期的产物,形成于与A型花岗岩类似的构造环境,因而暗示125Ma左右是长江中下游地区地壳强烈伸展的阶段。这一研究成果对探讨长江中下游地区早白垩世早期(135～140Ma)与晚期(约125Ma)左右的动力学背景具有重要的意义。  相似文献   

大别山超高压变质带中型花A岗岩确定及成因探讨     

钱存超  路玉林 《安徽地质》1999,(3)

大别山超高压带中变质花岗岩特征：（１） 岩石组合较单一,以二长花岗岩（ 原岩） 为主,缺乏中基性岩和正长岩类;（２） 具鳞片花岗变晶结构,片麻状构造,保留残存的岩浆岩组构;（３） 与榴辉岩及其它超高压变质岩石有明显侵入接触关系,并可见有其捕虏体;（４） 岩石化学表现为富硅、富碱、贫钙、贫镁等特征,一般地ＳｉＯ２ ＞ ７６ ％ ,（ Ｎａ２ Ｏ＋ Ｋ２ Ｏ） ＞ ８ ％ ,ＣａＯ＜ ０ ．５ ％ ,ＭｇＯ ＜ ０ ．４ ％ ;（５） 痕量元素表现为Ｚｒ 、Ｙ、Ｎｂ 、ＲＥＥ 含量高,Ｓｒ 、Ｓｃ 、Ｖ、Ｎｉ 等低;（６） 变质矿物组合为斜长石＋ 石英＋ 钾长石＋ 白云母＋ 石榴石＋ 绿帘石,属于低角闪岩相。（７） 锆石Ｕ － Ｐｂ 同位素年龄值为６８５ ±４１ Ｍａ 。大别山超高压变质带中变质花岗岩为Ａ 型花岗岩,更接近Ａ２ 亚类。变质Ａ 型花岗岩的确定,对进一步认识大别山的大地构造演化、榴辉岩等超高压变质带的形成、折返机制等提供了重要地质依据。  相似文献   

Generation of rhyolite magmas by melting of subducting sediments in Shodo-Shima island, Southwest Japan, and its bearing on the origin of high-Mg andesites   总被引：1，自引：0，他引：1  

G. Shimoda and  Y. Tatsumi 《Island Arc》1999,8(3):383-392

Abstract Geochemical characteristics of rhyolites from the Miocene Setouchi volcanic belt in the Southwest Japan arc were examined. The following observations may be best explained by the derivation of rhyolite magmas by melting of subducting sediments as follows. (i) Sr-Nd-Pb isotope compositions of Setouchi rhyolites are close to those of the local trench-fill sediments; (ii) major element compositions of rhyolites are identical to those of experimentally produced sediment melts; and (iii) concentrations of incompatible elements in rhyolites are consistent with partial melting of the local trench-fill sediments in the presence of residual garnet. Furthermore, trace element and isotope signatures of Setouchi high-Mg andesites can be also rationalized by interaction of such rhyolitic sediment melts with overlying mantle peridotites.  相似文献   

内蒙古阿巴嘎旗中元古代片麻状花岗岩锆石U-Pb年龄、地球化学特征及大地构造意义   总被引：1，自引：1，他引：0  

孙立新  张云  李艳锋  许凡  任邦方 《岩石学报》2020,36(3):781-798

在内蒙古阿巴嘎旗南部新发现一处面积约为9.2km2的片麻状正长花岗岩体,采用LA-MC-ICP-MS锆石U-Pb测年法获得该岩体的同位素年龄为1377±10Ma～1385±14Ma,属中元古代。它是继苏尼特左旗南部锡林浩特微地块的中元古代花岗岩发现后又一处中元古代片麻状正长花岗岩体。片麻状正长花岗岩具条纹状-弱片麻状构造,矿物组成为石英(25%～30%)、微斜长石(30%～40%)、条纹长石(15%～20%)、斜长石5%～10%以及少量黑云母(约5%)。其地球化学成分显示高SiO_2(76.05%～78.16%)、高碱(K_2O+Na_2O=6.69%～8.04%)和较高的K_2O/Na_2O比值(1.01～2.48),低TiO_2(0.17%～0.23%)、A1_2O_3(10.99%～11.97%)、MgO(0.08%～0.44%)和CaO(0.15%～0.37%),铝饱和指数A/CNK值均大于1.1,里特曼指数主体小于1.8,属于过铝质和钙质系列;并且它们具有稀土元素总量高,轻稀土富集而重稀土亏损的特征,显示强烈负铕异常(δEu=0.44～0.53)和高的10000Ga/Al比值(均值为4.43)。上述岩相学、地球化学组成均显示A型花岗岩的特点,暗示其形成于伸展环境。片麻状正长花岗岩锆石ε_(Hf)(t)值主体介于+0.5～+4.6,两阶段模式年龄t2DM为1.88～2.10Ga,表明岩浆可能来源于古元古代新增生地壳的部分熔融。阿巴嘎旗与苏尼特左旗中元古代岩体的发现为锡林浩特微地块的存在提供了直接证据。区域对比显示中亚造山带中的阿拉善微地块、中天山微地块、库鲁克塔格微地块和锡林浩特微地块上均具有～1.4Ga岩浆事件产物,可能是全球哥伦比亚超大陆裂解事件(1.5～1.3Ga)的岩浆响应。  相似文献   

云南安宁地区石虎山花岗岩年代学、地球化学特征和锆石Hf同位素组成及其成因          下载免费PDF全文

刘军平  孙柏东  崔晓庄  熊波  宋冬虎  白春东  张坤  杨仕潘 《中国地质》2020,47(3):693-708

石虎山花岗岩岩体位于安宁市德滋村附近,本文对该岩体开展了LA-ICP-MS锆石U-Pb定年、岩石地球化学、锆石Hf同位素组成研究。结果获得(616±20) Ma的岩浆结晶年龄和(839±17) Ma、(766±15) Ma、(705.5±9.4) Ma的继承性年龄,说明岩体形成于新元古代埃迪卡拉纪;其中(839±17) Ma、(766±15) Ma、(705.5±9.4) Ma的继承性年龄组合可能是Rodinia超大陆裂解构造过程的记录,839 Ma、616 Ma可能是Rodinia超大陆在扬子板块西缘开始裂解与最终裂解时限。花岗岩主量、微量元素特征显示,其产生于伸展环境的高硅、过铝、高钾的A型花岗岩;锆石ε_(Hf)(t)值均小于0,在t-t(Ma)和t-(~(176)Hf/~(177)Hf)图上,所有样品点均落在上地壳演化线之上,二阶段模式年龄变化范围为1.77～2.31 Ga,结合Nb/Y—Rb/Y图解,表明成岩物质主要来源于古元古代古老下地壳页岩60%部分熔融。  相似文献   

Mineralogical and geochemical characteristics of hydrothermal alteration and episyenitization in the Königshain granites, northern Bohemian Massif, Germany     

L. Hecht  K. Thuro  R. Plinninger  M. Cuney 《International Journal of Earth Sciences》1999,88(2):236-252

The late-Hercynian granites of Königshain underwent multistage hydrothermal processes. Extensive high-temperature late-magmatic alteration is, for example, indicated by low Zr/Hf and an REE pattern displaying the tetrad effect. Intensive post-magmatic alteration of the granite occurred along brittle structures. At least two main stages of post-magmatic hydrothermal alteration are involved. The first high-temperature stage, which is characterized by albitization and/or quartz leaching (episyenitization), resulted from fluid–rock interaction with late-magmatic fluids that very probably mixed with external low-salinity fluids. Quartz dissolution was triggered by vapour condensation and/or the cooling of these fluids (below 450??°C) along brittle structures. The high porosity resulting from quartz leaching during stage 1 assisted subsequent circulation of low-temperature fluids at stage 2; the latter is characterized by the chloritization and illitization of episyenites. Almost all major and trace elements were enriched or depleted during one of the main alteration stages. However, Zr, Hf, Th, and Ti were immobile during post-magmatic alteration. The significant depletion of LREE and the enrichment of HREE in albitized samples is controlled by the dissolution of monazite and the new formation of HREE-rich polycrase-(Y) or aeschynite-(Y) during post-magmatic stage 1. Negative Ce anomalies of episyenites are associated with illitization and suggest oxidizing conditions during stage 2.  相似文献   

小兴安岭东部清水岩体的锆石激光探针U-Pb年龄测定   总被引：46，自引：0，他引：46  

孙德有  吴福元  高山 《地球学报》2004,25(2):213-218

本文应用锆石激光剥蚀等离子质谱 (LA ICPMS)定年技术 ,测得小兴安岭东部清水岩体的侵位年龄为 2 2 2± 5Ma。岩石学和地球化学研究显示 ,该岩体为过碱性A型花岗岩 ,属于A2 型或PA型 ,形成于造山后构造环境 ,与华北板块和西伯利亚板块在二叠纪末期碰撞拼合后的岩石圈伸展作用有关。  相似文献   

青藏高原西南部查孜地区中新世钾质火山岩地球化学及其成因   总被引：4，自引：1，他引：3  

陈建林  许继峰  康志强  王保弟 《地球化学》2007,36(5):437-447

通常认为青藏高原的钾质-超钾质火山岩的形成多与地幔有着紧密的联系,然而最近对青藏高原的一些钾质-超钾质火山岩的研究显示一些钾质火山岩也可以起源于下地壳.青藏高原西南部查孜地区中新世火山岩是形成于13～11 Ma左右的一套钾质-超钾质岩石,根据岩石化学组成将其分为中基性火山岩组、中性火山岩组和流纹质火山岩.其中中基性火山岩组可能源于一个富含金云母的富集地幔源区;中性火山岩组可能是富钾的镁铁质下地壳部分熔融的产物;流纹质火山岩可能是拉萨地块在中新世时期的伸展构造运动而导致中上地壳因减压而发生部分熔融的产物.结合查孜地区及其邻近火山岩的年龄、化学组成以及岩浆组合,初步认为查孜地区火山岩可能与高原在中新世发生伸展活动而产生的南北向地堑系统有关.  相似文献   

The Origin of Mesozoic A-type Granitoids, Fujian Province, Southeast China: Insights from Geochronology, Mineralogy and Geochemistry     

XIE Qifeng  DONG Yunpeng  CAI Yuanfeng  ZHAI Mingguo  XIAO Aifang  ZHANG Hong 《《地质学报》英文版》2024,98(3):630-640

The magma sources, origins and precise forming ages of the miarolite from Qishan and Kuiqi intrusions are still uncertain. New results reveal that, miarolites from the Qishan and Kuiqi intrusions yield crystallization ages of ~101 and ~98 Ma, and they have a high formation temperature (~910°C) and low oxygen fugacity value, indicating crystallization condition at low pressure in the upper crust with temperature of 678°C. The Qishan and Kuiqi miarolites are characterized by enrichment in SiO2 and high-K alkali, depletion in Ca and Mg, and belong to the high-K weak peraluminous rock series. The samples are enriched in HFSEs (i.e., Ta, Zr and Hf) and LILEs (i.e., Ba, P and Sr), depleted in Ba and Sr with the negative anomaly of Eu. In the primitive mantle normalized trace element spider diagram, the samples show a right-inclined ''seagull-type'' pattern, combined the ratios of (La/Yb)N, 10000 × Al/Ga, Rb/Nb and Nb/Ta etc., they were proved to be alkaline A-type granite. Combined the characterize of the trace elements, they were derived from clay-rich source accompanied pelite melting, and subjected to K-feldspar crystallization fractional. The values of εHf(t) and tDM2 are distributed in the range of ?2.8 to 3.3 with ~1.2 Ga, and ?6.0 to 4.0 with ~1.2 Ga, revealing that they were generated from the Mesoproterozoic Cathaysia basement rocks. The comprehensive research reveals the Kuiqi and Qishan intrusions derived from crust-mantle mixing and partial melting of the crust, respectively, resulting from lithospheric extension generated by the Paleo-Pacific Plate subducted into the European–Asian Plate.  相似文献