张广才岭北部苇河花岗岩基的地球化学特征与岩石成因     

李蓉  孙德有  苟军  魏红艳  柳小明  武鹏飞  刘玮 《世界地质》2012,31(3):462-470

张广才岭北部苇河花岗岩基的地质学、岩相学、全岩主量和微量及锆石Hf 同位素的详细解析显示: 苇河花岗岩基主体岩性为花岗闪长岩、二长花岗岩、正长--碱长花岗岩及少量的石英闪长岩和英云闪长岩,不同岩石类型之间呈侵入接触关系。岩石富硅富铝,为准铝质--弱过铝质岩石( A/CNK = 0. 97 ～ 1. 03) ,全碱( K₂O + Na₂O) 含量为6. 56% ～ 9. 10%,主要为高钾钙碱性系列I 型花岗岩。稀土和微量元素组成上,均富集LREE、Rb、Th、U、K、Hf,相对亏损Nb、Ta、P、Ti,δEu 从中等程度负异常到弱正异常。不均匀的锆石Hf 同位素成分( εHf ( t) = ( － 6. 68 ～ + 12. 13) ,TDM2 = 464 ～ 1 657 Ma) 表明,岩浆主体来源于显生宙--新元古代时期从亏损地幔中增生的基性下地壳物质,局部同化了更古老的地壳物质。  相似文献   

The Late Neoproterozoic granitoid magmatism of the Pelotas Batholith, southern Brazil     

Ruy Paulo Philipp  Rmulo Machado 《Journal of South American Earth Sciences》2005,19(4):117

Geological mapping, petrography, geochemistry, and isotope studies enable the division of the Pelotas Batholith into six granitic suites: Pinheiro Machado (PMS), Erval (ES), Viamão (VS), Encruzilhada do Sul (ESS), Cordilheira (CS), and Dom Feliciano (DFS). The rocks of the PMS show a large compositional range (granite through granodiorite to tonalite), and the suite is considered pre- to syncollisional. Other suites show restricted compositional variations (granite to granodiorite) and are late to postcollisional. In general, the suites are metaluminous to slightly peraluminous (PMS, ES, and VS) or peraluminous (CS) or have alkaline tendencies (ESS and DFS). The magmatic evolution corresponds to high-K calc-alkaline to alkaline magmatism. The suites are enriched in K, Rb, and REE compared with rocks of typical calc-alkaline series. Initial ⁸⁷Sr/⁸⁶Sr ratios vary from 0.705 to 0.716, except in the CS, where they attain values of 0.732–0.740. Sm–Nd T_DM model ages vary between 0.98 and 2.0 Ga, with initial ε_Nd values ranging from −0.3 to −10. U–Pb zircon dates of samples from PMS, VS, and ESS suggest an age between 0.63 and 0.59 Ga for magmatism. Rb–Sr dates of samples of alkaline granites from DFS present ages between 0.57 and 0.55 Ga. The main tectonic controls of the magmatism of the Pelotas Batholith are high-dip sinistral shear zones.  相似文献   

北京云蒙山花岗岩基的岩石变形及其成因   总被引：6，自引：0，他引：6       下载免费PDF全文

许继峰  王人镜 《地球科学》1994,19(6):806-814

云蒙山花刚岩基由１２个侵入体组成，岩基中的片麻状花岗岩是在１２６±２１Ｍａ时侵入的型花岗岩，根据岩基中花岗岩与围岩的变形循征，确定岩基的侵位机制为底辟定位型，花岗岩中的变形组构与环绕岩基的糜棱岩的岩基定位晚期、花岗岩浆完全结晶之前形成。由于云蒙山花岗岩基的强力定位，导致密怀变质核杂岩在燕山晚期再次发生伸展构造运动。  相似文献   

古特提斯缝合带澜沧江段花岗岩高温高压实验模拟   总被引：3，自引：0，他引：3  

刘海龄  王子江  施小斌  丘学林  张伯友  阎贫  夏斌 《热带海洋学报》2004,23(2):10-18

对古特提斯主体遗迹的云南西部昌宁-孟连构造混杂缝合带、临沧花岗岩基、澜沧江韧性变形变质带进行了岩石高温高压三轴变形实验模拟研究．以期对该构造带形成时期所处的构造物理环境作出判断。实验岩洋取自紧邻澜沧江韧性剪切变形变质带西侧的临沧花岗岩基。实验后样品产生了一系列新生显微构造，对应的地壳深度环境相当于中下地壳(13-18km)。澜沧江韧性变形变质带花岗岩的显微组构以动力重结晶颗粒极为发育为特征，表明其形成时的环境远比实验深度更深。综合考虑临沧花岗岩基现在的厚度(达15km)和花岗岩浆流动的上限深度(8-10km)以及风化剥蚀量．可以认为临沧花岗岩基的形成深度可大于25km，原始岩浆源于下地壳下部．接近莫霍面的顶面。澜沧江韧性变形变质带的形成与临沧岩基向东逆冲相关．它直抵古特提斯俯冲板块下插滑动顶面。研究表明，昌宁-孟连古特提斯曾发生过真正意义上的大规模洋壳俯冲．是一个具有较大规模的古洋盆。  相似文献   

Petrology,geochemistry and thermobarometry of the northern area of the Flamenco pluton,Coastal Range batholith,northern Chile. A thermal approach to the emplacement processes in the Jurassic andean batholiths     

《Journal of South American Earth Sciences》2016

The Flamenco pluton is part of a N–S alignment of Late Triassic to Early Jurassic intrusive belt comprising the westernmost part of the Coastal Range batholith in northern Chile. The Jurassic-Cretaceous voluminous magmatism related to subduction in the western active continental margin of Gondwana is emplaced in the predominantly metasedimentary Paleozoic host-rocks of the Las Tórtolas formation, which in the northern area of the Flamenco pluton present an intense deformation, including the Chañaral mélange.Geochemically, the Flamenco pluton shows a wide compositional variability (SiO₂ between 48wt % and 67wt %). Gabbros, Qtz-diorites and tonalites, mesocratic and leucocratic granodiorites are classified as calc-alkaline, calcic, magnesian and metaluminous magmatism. Flamenco granitoids define cotectic linear evolution trends, typical of magmatic fractionation processes. Geochemical trends are consistent with magmas evolved from undersaturated and low-pressure melts, even though the absence of transitional contacts between intrusive units precludes in-situ fractionation. Although some granodioritic samples show crossed geochemical trends that point to the compositional field of metasediments, and large euhedral prismatic pinnite-biotite crystals, typical Crd pseudomorph, are observed in contact magmatic facies, geochemical assimilation processes are short range, and the occurrence of host-rocks xenoliths is limited to a few meters from the pluton contact.A thermal approach to the emplacement process has been constrained through the thermobarometric results and a 2D thermo-numerical model of the contact aureole. Some Qtz-diorites and granodiorites located in the north area of the pluton exhibit granulitic textures as Hbl-Pl-Qtz triple junctions, poikiloblastic Kfs and Qtz recrystallization. The Hbl–Pl pairs have been used for the thermobarometric study of this metamorphic process, resulting granoblastic equilibrium temperatures between 770 and 790 °C, whereas Hbl–Pl pairs in domains that preserve the original igneous textures yield temperatures above 820 °C. This is characteristic of self-granulitization processes during the sequential emplacement of composite batholiths.In addition, the thermal modeling was used in order to compare the expected and observed thermal contact aureole of the intrusive body. Model P-T conditions have been established between 3 and 4 kbars (extracted from the thermobarometric results), and temperatures between 1159 °C (liquidus temperature for a tonalitic composition) and 992 °C (fixed at the rheological threshold of a 50% crystal fraction). The thermal modeling estimates a homogeneous contact aureole, where the established temperatures for the melting reactions in the host-rocks are located at distances between 200 and 650 m from the magma chamber boundary, whereas the temperatures for Crd stabilization extend 1500 m far from the contact in the case of the emplacement at liquidus temperatures and 4 kbars. According to field observations, the contact aureole presents a scarce development in the northern area of the Flamenco pluton, with few migmatite outcrops and less than 1 Km in thickness for Crd-schists. However, in the southern contact, partially melted rocks are described at distances up to 2 km from the Flamenco pluton boundary.The processes of self-granulitization and the differences between the observed and calculated (by the thermal modeling of one single pulse) contact aureole suggests a process of incremental emplacement for the Flamenco pluton, by accretion of magmatic pulses from north to south (in its current position), where the thermal maturity reached through the repeated magmatic intrusion generates a more extensive area of high-grade metamorphism.  相似文献   

藏南冈底斯南缘程巴岩体高Sr/Y花岗闪长岩和包体形成机制及Sr-Nd-Hf同位素制约   总被引：1，自引：0，他引：1  

尚振  曾令森  高利娥  高家昊  陈福坤  侯可军  王倩  郭春丽 《地质通报》2016,35(1):71-90

程巴岩体位于藏南冈底斯岩基东段南缘,由花岗闪长岩、细粒闪长质包体等组成。测得的锆石U-Pb年龄可以代表岩石的形成年龄,即花岗闪长岩形成年龄为29.40±0.18Ma与29.42±0.25Ma,细粒闪长质捕虏体形成年龄为30.02±0.15Ma。花岗闪长岩具有较高的Si O2(65.2%~66.2%)、K2O(3.2%~4.0%),较低的铁(TFe O=3.2%~4.0%)和Mg O(约2%),同时具有高Sr(774×10-6~813×10-6)、低Y(9.9×10-6~11.2×10-6)、高Sr/Y值(63.4~82.2)等特征;闪长质包体表现出较低的Si O2(53%~56.1%)和K2O(1.5%~3.2%),较高的铁(TFe O=6.1%~8.1%)、Mg O(4.0%~6.2%)和Na2O/K2O≥2,同时具有负Eu异常(Eu/Eu*=0.432~0.804)。2种岩性都富集LREE及LILE,亏损HREE及HFSE,具有较高且一致的εHf(t)值(+1.1~+6.2)和全岩εNd(t)值(-2.9~-5.9)。以上数据表明,花岗闪长岩与细粒闪长质包体由同一岩浆分离结晶形成,花岗闪长岩经历磷灰石和角闪石的分离结晶,其高Sr/Y值为岩浆分离结晶的结果,并不代表原始岩浆组分。  相似文献   

天山东部冰川雪坑离子浓度特征的对比研究——以奎屯河哈希勒根51号冰川和哈密庙尔沟平顶冰川为例   总被引：2，自引：0，他引：2  

李向应  刘时银  韩添丁  李忠勤  卢爱刚 《地球科学进展》2008,23(12)

对2004年获取的天山奎屯河哈希勒根51号冰川1个雪坑和哈密庙尔沟平顶冰川4个雪坑的离子浓度特征进行了研究,结果表明:Ca2 、NO3-和SO24-是哈密庙尔沟平顶冰川雪坑雪层和积累区雪坑底部冰中的主要离子(尤其是Ca2 ),其雪层中的主要阳离子关系可在底部冰中得以较好的反映,但雪层中各离子浓度与海拔的相关性不明显,可能与海拔的跨度较小和挖取的雪坑较疏有关;雪坑底部冰中的离子浓度与海拔间明显的相关性说明淋融作用随着海拔升高、气温降低而逐渐减弱。SO24-和Ca2 是奎屯河哈希勒根51号冰川雪坑中的主要离子(尤其是SO42-),其雪坑离子化学特征与哈密庙尔沟平顶冰川差别较大,可能与哈密庙尔沟平顶冰川处于塔克拉玛干沙漠、古尔班通古特沙漠和鄯善沙漠的下风向相关,还可能与雪层内淋融作用的强弱和沉积通量的高程效应有关。哈密庙尔沟平顶冰川积累区雪坑中NH4 、NO3-和K 的Cs/Ci较Ca2 、Mg2 和Na 要大,奎屯河哈希勒根51号冰川Na 和NH4 的"雪冰比"较Cl-、SO42-、Mg2 和Ca2 要大,说明这两条冰川雪坑中的Ca2 和Mg2 信号较其它离子可能更易于在冰芯记录中保存下来,为冰芯研究和古气候记录的恢复提供了保障。  相似文献   

天山东部冰川雪坑离子浓度特征的对比研究     

李向应  刘时银  韩添丁  李忠勤  卢爱刚 《地球科学进展》2008,23(12):1268-1276

对2004年获取的天山奎屯河哈希勒根51号冰川1个雪坑和哈密庙尔沟平顶冰川4个雪坑的离子浓度特征进行了研究,结果表明：Ca²⁺、NO^-3和SO₄^2-是哈密庙尔沟平顶冰川雪坑雪层和积累区雪坑底部冰中的主要离子（尤其是Ca²⁺ ）,其雪层中的主要阳离子关系可在底部冰中得以较好的反映,但雪层中各离子浓度与海拔的相关性不明显,可能与海拔的跨度较小和挖取的雪坑较疏有关;雪坑底部冰中的离子浓度与海拔间明显的相关性说明淋融作用随着海拔升高、气温降低而逐渐减弱。SO₄^2-和Ca²⁺是奎屯河哈希勒根51号冰川雪坑中的主要离子（尤其是SO₄^2-）,其雪坑离子化学特征与哈密庙尔沟平顶冰川差别较大,可能与哈密庙尔沟平顶冰川处于塔克拉玛干沙漠、古尔班通古特沙漠和鄯善沙漠的下风向相关,还可能与雪层内淋融作用的强弱和沉积通量的高程效应有关。哈密庙尔沟平顶冰川积累区雪坑中NH₄⁺、NO₃^-和K⁺的Cs/Ci较Ca²⁺、Mg²⁺和Na⁺要大,奎屯河哈希勒根51号冰川Na⁺和NH4⁺的“雪冰比”较Cl-、SO₄^2-、Mg²⁺和Ca²⁺要大,说明这两条冰川雪坑中的Ca²⁺和Mg²⁺信号较其它离子可能更易于在冰芯记录中保存下来,为冰芯研究和古气候记录的恢复提供了保障。  相似文献   

福建武平岩基岩石谱系单位划分   总被引：1，自引：0，他引：1  

马金清  冯宗帜 《福建地质》1998,17(4):177-187

根据近几年来在１：５万区调中采用岩石谱系单位新理论、新方法填图的成果,以及岩石成分、结构构造特征、群居关系、侵入接触类型等,将过去１：２０万区调均划属燕山早期黑云母花岗岩及细粒花岗岩的武平岩体,解体为志留纪、晚三叠世、侏罗纪、白垩纪等不同时代深成岩体,划分出中（基）性、中酸性及酸性岩等岩石类型。圈定深成岩体４０个,独立侵入体１５个,共３３个单元,归并为６个超单元,５个独立单元。并认为志留纪侵入岩浆  相似文献   

浙江景宁花岗岩基的解体划分及其演化     

王天德  曹金用 《地质通报》1998,(4)

根据同源岩浆演化的观点,运用岩石谱系单位的划分方法,将景宁花岗岩基解体,划分为９个单元,归并成２个超单元。岩体定位方式为断裂扩张型。  相似文献