Geochronological and geochemical characteristics of fractionated I-type granites associated with the skarn mineralization in the Sangan mining region,NE Iran     

《Ore Geology Reviews》2017

The Sangan mining region, which has a proven reserve of approximately 1000 Mt of 53% iron ore, is located in the Khaf-Kashmar-Bardeskan volcano-plutonic belt in northeastern Iran. The geological units in the eastern zone of the Sangan region consist of Precambrian schists, Jurassic sedimentary rocks and Tertiary subvolcanic granitoid intrusions. Iron skarn mineralization consists of stratiform and massive bodies in the carbonate rocks that are adjacent to the granitoid intrusions. Detailed field mapping revealed that 39-Ma syenitic intrusive bodies in the western and central zones of the Sangan region were the main sources of heat and fluid for the iron mineralization.A Mid-Cenozoic biotite granite pluton is associated with the eastern anomalies. However, field relationships suggested that this pluton is not the source of the metals, heat or fluids that were responsible for the iron mineralization. This pluton is rich in silica (SiO₂ contents from 66.4 to 79.1 wt%) and is characterized by high-K series with metaluminous to slightly peraluminous affinity.Geochronological (U-Pb zircon method) and geochemical data, including major and trace elements and Sr-Nd-Pb isotopes, define the complex origin of these plutons, which consist of alkaline granitoids that appear to be A-type in character but also show I-type affinity.New geochemical and isotopic data from plutons in the eastern anomalies and data from previous studies of the western and central anomalies and the southeastern intrusive rocks in the Sangan region show that these plutons have close affiliation with lower to upper crust-derived melts and were largely modified into highly fractionated I-type granite. These rocks were derived from and emplaced by varying degrees of partial melting during the Middle Eocene (Bartonian to Lutetian, 38.3–43.9 Ma) from a crustal protolith in a normal to mature volcanic continental arc setting.The Sangan granitoids were produced from crustal assimilation by a heat source from mantle melts, which are associated with the Kashmar-Neotethyan slab that subducted under Eurasia. The Khaf-Kashmar-Bardeskan igneous rocks reflect an active Cenozoic plate margin that was related to the closure of the Kashmar-Neotethyan Sea between the Lut and Eurasia blocks because of the continuous convergence between the Arabian and Iran plates during the Late Cretaceous–Early Paleocene.  相似文献   

松潘造山带金川地区观音桥晚三叠世二云母花岗岩的成因及其地质意义     

朱毓  赖绍聪  秦江锋 《地质论评》2017,63(6):1465-1478

松潘造山带内发育大量印支期花岗岩,这些花岗岩类对于该地区岩浆活动、基底性质和构造演化的研究有着重要的意义。金川地区观音桥二云母花岗岩位于松潘造山带东部,属于晚三叠世花岗岩。岩石具有高硅(SiO_2=72.08%~73.95%)、富碱(K_2O=4.44%~5.84%、Na_2O=3.29%~3.93%)的特征,其A/CNK值为1.08~1.22,属于过铝质高钾钙碱性S型花岗岩类。岩石富集大离子亲石元素,亏损部分高场强元素,具有明显的Eu负异常(δEu=0.26~0.38)。观音桥二云母花岗岩的ε_(Nd)(t)=-7.9~-10.1(平均为-8.9)不高,Nd同位素二阶段模式年龄T_(2DM)值为1.42~1.57 Ga,显示源岩应该为中元古代地壳岩石。岩石高的Rb/Sr值和低的CaO/Na_2O值、较低的Al_2O_3/TiO_2值和低的Rb/Ba值,表明其起源于泥质源岩的部分熔融。综合地球化学、同位素特征和区域地质资料,笔者等认为金川地区观音桥二云母花岗岩是在松潘造山带挤压背景下,由中—上地壳泥质源岩发生部分熔融而形成。  相似文献   

广西岑溪地区糯垌A型花岗岩的厘定及其构造意义     

李程 《地质与勘探》2017,53(6):1090-1104

广西糯垌岩体位于华夏古陆与钦杭结合带的交接部位,主要岩性为黑云母钾长花岗岩,其锆石LA-ICP-MS U-Pb年龄为(151.1±1.9)Ma和(152.6±1.2)Ma,显示为燕山早期晚侏罗世岩浆活动的产物。糯垌岩体具有富碱、高钾、高铁、贫镁的特征,alk的质量分数为10.29%~10.91%,Fe OT的质量分数为3.60%~5.10%,Fe OT/Mg O值为10.33~11.69。岩石为碱性准铝质系列,δ43为4.78~5.38,A/CNK值为0.96~0.98,A/NK值为1.21~1.24;具有右倾型的稀土配分模式图,稀土总量较高,具强烈的负铕异常,其∑REE值为(610.03~790.48)×10~(-6),δEu值为0.30~0.37。原始地幔标准化蛛网图显示明显亏损Ba、Sr、P、Ti,富集Rb、Th、La、Ce、Zr、Hf、Y等元素;具有较高的10 000Ga/Al值(3.03~3.31)和Zr+Nb+Ce+Y值((857.7~1244.4)×10~(-6))。上述地球化学特征表明糯垌岩体为铝质A型花岗岩,同时具较低的Ce/Nb、Y/Nb、Yb/Ta元素比值,暗示为A1型非造山花岗岩。εNd(t)值为-2.25~-1.52,εSr(t)值为22.34~37.59,TDM值为(0.86~1.24)Ga,表明糯垌岩体来源于中新元古代的地壳物质,可能有地幔物质的参与。糯垌岩体形成于板内环境,说明广西岑溪地区晚侏罗世经历特提斯构造域向太平洋构造域转换后进入板内非造山构造环境。  相似文献   

辽东黄花甸地区古元古代花岗质岩浆作用及其地质意义   总被引：5，自引：4，他引：1  

王鹏森  董永胜  李富强  高铂森  甘宜成  陈木森  许王 《岩石学报》2017,33(9):2708-2724

胶-辽-吉古元古代造山/活动带的辽东黄花甸地区出露大量古元古代花岗质岩石,前人将该区的花岗质岩石统称为花岗质混杂岩。本文通过详细的野外地质调查和室内综合研究,将该套花岗质混杂岩解体为时代及性质完全不同的两类花岗岩——黑云母二长花岗岩和花岗闪长岩。其中黑云母二长花岗岩具有块状、条痕状、片麻状的不同构造类型,均显示富SiO_2(72.37%~77.44%)、贫Al_2O_3(11.69%~13.21%)、富K_2O(3.97%~5.11%)的特征,Na_2O/K_2O=0.64~1.08,TiO_2含量在0.18%~0.34%之间,MnO、MgO和P_2O_5的含量较低,分别为0.01%~0.07%、0.12%~0.32%和0.01%~0.06%,铝饱和指数A/CNK集中分布在1.33~1.45之间,A/NK在1.49~2.60之间,属于过铝质高钾钙碱性系列;微量元素Sr、Ba、Ti、P强烈亏损,具有明显的Eu负异常,具有A型花岗岩的特征。黑云母二长花岗岩的锆石大部分为具有清晰震荡环带结构的岩浆锆石,从3个样品获得LA-ICP-MS锆石U-Pb谐和年龄分别为2185±29Ma、2183±13Ma、2166±10Ma,据目前所获得南辽河群碎屑锆石年龄(1.95~2.15Ga),本文认为黑云母二长花岗岩的侵位时代要早于南辽河群地层沉积的时间,构成了南辽河群地层沉积的基底。花岗闪长岩呈岩枝状侵入黑云母二长花岗岩和里尔峪组地层中,富SiO_2(72.54%~74.31%)、Al_2O_3(15.01%~16.17%),全碱(K_2O+Na_2O)平均7.77%,相对富钠(Na_2O/K_2O=1.27~2.82),贫钙、镁,MgO平均为0.26%,CaO平均为1.59%,Mg#值平均为54.0,铝饱和指数A/CNK集中分布在1.61~1.78之间,A/NK在1.49~2.60之间,属于过铝质钙碱性系列,具明显的Eu正异常,Y/Yb低,Sr/Y高,而且强烈亏损Th、Ta、Nb、Ti等高场强元素,富集Ba、K、Rb、Sr等低场强元素,具有埃达克质花岗岩的特征。花岗闪长岩的锆石大部分为具有清晰震荡环带结构的岩浆锆石,从2个样品获得LAICP-MS锆石U-Pb年龄分别为1995±18Ma、1995±13Ma。可以推断花岗闪长岩的侵位时代为2.0Ga左右。本文认为具有A型特征的黑云二长花岗岩是陆块内部拉伸减薄-裂解过程中下部地壳部分熔融的产物,具有埃达克质特征的花岗闪长岩是俯冲过程中所形成火山弧或活动大陆边缘岩浆活动的产物。以上研究表明胶-辽-吉古元古代造山/活动带可能经历了在2.2~2.15Ga左右的拉伸裂解过程和2.0Ga左右俯冲挤压的构造演化过程。  相似文献   

西大别造山带夏店岩体锆石U-Pb年代学、地球化学特征及其A型花岗岩的厘定     

万俊  吴波  郭盼  刘万亮  刘成新 《岩石矿物学杂志》2017,36(5):633-645

对西大别造山带夏店岩体进行了系统的锆石LA-ICP-MSU-Pb定年、岩石地球化学研究,发现该岩体化学成分具富硅、碱,贫钙、镁、铝等特点;岩石轻稀土元素富集,重稀土元素亏损,轻重稀土元素分馏明显,Eu亏损明显;Rb、K、Th等大离子亲石元素和Pb元素富集,Ta、Nb、Ti等高场强元素亏损和Sr、Ba元素亏损;岩石成因类型上属于A型花岗岩。LA-ICP-MS锆石U-Pb定年结果显示夏店岩体~(206)Pb/~(238)U加权平均年龄为130.0±1.8 Ma,代表岩体的结晶年龄,显示该岩体为早白垩世岩浆活动的产物。夏店岩体A型花岗岩形成于造山期后环境,预示着桐柏-大别造山带板内演化阶段的到来。  相似文献   

江南造山带西段岩浆作用特性   总被引：12，自引：1，他引：11  

周金城  王孝磊  邱检生 《高校地质学报》2005,11(4):527-533

在湖南浏阳南桥的中元古代冷家溪地层中发现了一种高度亏损、具N—MORB属性的玄武岩一辉绿岩。这种玄武岩的K2O特低,不相容的高场强元素,如Nb,Zr,Hf,Ti等和稀土元素的丰度都低于（少数元素接近）N-MORB的丰度,εNd（1271Ma）为6．86～8、98。在俯冲带附近N—MORB的发现为“九岭古岛弧”的存在提供了新的证据。湘西黔阳、古丈新元古代玄武岩-辉绿岩属碱性玄武岩．其微量元素特征近似于OIB,它的规模值得进一步调查。广西北部丹洲群中基性-超基性岩的TiO2,Ta及Nb的含量低,Hf／Th,Ti／Y和Ti／Zr等的比值也低,La/Ta和Th／Yb等的比值高,具有“弧玄武岩”特性。它们不具有CFB及OIB的地球化学特征,在构造环境判别图解上的标绘点集中在“火山弧玄武岩区”,少数样品位于“弧后盆地玄武岩区”。至今未发现具高温特征的高镁熔岩,也未见大规模放射性岩墙群。这些基性岩的规模极小（约100km^2）,不具有地幔柱来源的镁铁质岩浆的特性。桂北及湘东北的新元古代强过铝（SP）花岗岩体与江西九岭和安敞许村、休宁、歙县等岩体具有相似的特征,它们沿江南造山带呈带状分布,其形成与华夏和扬子板块之间的碰撞事件有关。在全球不同时代的造山带中都有S-型花岗岩出露;地幔柱岩浆作用形成的“镁铁质大火成岩省”中,出现的少量花岗岩是非造山、板内或A-型花岗岩,而不会是S-型花岗岩。不能把S-型花岗岩作为地幔柱岩浆作用的证据。这些都说明“江南造山带”的厘定有充分的岩石学证据。  相似文献   

Petrology,geochronology and Sr–Nd isotopic geochemistry of the Konso pluton,south-western Ethiopia: implications for transition from convergence to extension in the Mozambique Belt     

Asfawossen?AsratEmail author  Pierre?Barbey 《International Journal of Earth Sciences》2003,92(6):873-890

Granites were shown to be excellent geochronological, structural and geodynamic markers. Among several generations of granites described in the Neoproterozoic of Ethiopia, we studied the post-tectonic Konso pluton to characterise the post-Pan-African evolution of the Mozambique Belt (MB) of southern Ethiopia. The Konso pluton is a composite intrusion of slightly peraluminous and ferro-potassic, bt (biotite)–leucogranites, bt–hbl (hornblende)–granites and subordinate coeval metaluminous monzodiorites, intruded into high-grade gneiss–migmatite associations of the MB. The whole suite displays chemical features of A-type granites. It is LIL- and HFS-elements enriched with Y/Nb and Yb/Ta1.2. The granites and leucogranites show non-fractionated to fractionated REE patterns [(La/Yb)_N=0.3–9.4] with strong negative Eu anomalies. The monzodiorites show fractionated REE patterns [(La/Yb)_N=5.5–7.4] with negligible negative Eu anomaly. The low initial (⁸⁷Sr/⁸⁶Sr)₄₅₀ ratios (0.70113–0.70441) and positive Nd₍₄₅₀₎ values (+1.8 to +3.3) suggest an isotopically primitive source. The Konso granites are likely to be derived from a basaltic parent, with minor contamination by crustal material with high Y/Nb and low Sr initial isotopic ratios. Age of pluton emplacement is constrained by a Rb–Sr isochron and zircon U–Pb data at 449±2 Ma. The Konso pluton is, therefore, the witness of an Ordovician A-type magmatic event, which marks a change from convergence, related to the Pan-African collision, to extension in the Mozambique Belt of southern Ethiopia.  相似文献   

鲍尔羌吉韧变花岗岩类地质特征   总被引：1，自引：1，他引：0  

李卫东  付延龙  李文铅 《新疆地质》2000,18(2):129-135

产于新疆东准噶尔红柳峡南扎曼苏－鲍尔羌吉变形带蝇的鲍尔羌吉超单元以强烈塑性变形为特征,形成于加里东早期造山运动大陆弧环境,属壳幔混熔的Ｉ型花岗岩。  相似文献   

Granites and granitic magmas: strange phenomena and new perspectives on some old problems   总被引：1，自引：0，他引：1  

J.D. Clemens 《Proceedings of the Geologists' Association. Geologists' Association》2005,116(1):9-16

  相似文献   

广东信宜-罗定地区含锡花岗岩类的稀土元素地球化学特征和成因   总被引：1，自引：0，他引：1  

陈炳辉  黄志国  俞受鋆  周永章 《矿产与地质》2005,19(5):465-468

广东信宜-罗定地区含锡花岗岩类呈复式小岩体产出,由花岗斑岩和花岗岩组成.岩石的稀土元素总量高(w(ΣREE)为236.75×10-6～383.28×10-6);从第一阶段花岗斑岩到第二阶段花岗岩的稀土总量降低;轻重稀土的比值ΣCe/ΣY(0.77～1.38)较低;具有弱的Ce负异常和强烈Eu亏损(δEu=0.015～0.119);稀土元素配分模式呈海鸥型.岩石属于大陆板内张性构造环境下高侵位形成的壳源重熔型花岗岩类.  相似文献