拉萨地块南木林盆地北缘中新世高锶低钇岩浆作用:锆石U-Pb年龄、Hf同位素和地球化学特征   总被引：1，自引：0，他引：1       下载免费PDF全文

付燕刚  胡古月  高一鸣  杨宗耀  林彬 《地质论评》2017,63(3):643-658

拉萨地块南木林盆地北缘的林子宗群火山岩地层侵位有大量的花岗斑岩岩株和岩脉,空间分布上与南北向正断层的次级断裂相一致。本次研究对南木林盆地北缘的花岗斑岩进行了系统的元素地球化学,LA-MCICP-MS锆石U-Pb年代学和Lu-Hf同位素测试。数据结果表明:花岗斑岩具有高硅(68.31%~71.34%)、高钾(4.52%~4.96%)、高(La/Yb)N(21.59~36.81)、Sr/Y(Sr/Y=15.59~38.10)等特征,富集大离子亲石元素(LILE),亏损高场强元素(HFSE);花岗斑岩LA-MC-ICP-MS锆石U-Pb年龄为12.2±0.1Ma,ε_(Hf)(t)值为-0.6~+4.0。拉萨地块南木林盆地北缘花岗斑岩岩石学、地球化学特征显示其为新生下地壳部分熔融产物,且源区残留了石榴子石、金红石、角闪石,无斜长石残留,在岩浆上侵过程中,发生了碱性长石的分离结晶作用。花岗斑岩侵位于中新世,与区内南北向裂谷发育时代一致,成分上类似于拉萨地块南部同时期发育的高锶低钇斑岩、钾质岩,同为印度—欧亚大陆碰撞后东西向伸展背景产物。  相似文献   

Geology, Geochemistry and Zircon U-Pb Geochronology of Porphyries in the Dabate Mo-Cu Deposit, Western Tianshan, China: Petrogenesis and Tectonic Implications     

DUAN Shigang  ZHANG Zuoheng  WANG Dachuan  LI Fengming 《《地质学报》英文版》2017,91(2):530-544

The Dabate Mo-Cu deposit is a medium-sized porphyry-type deposit in the Sailimu Lake region, western Tianshan, China. We present the geology, geochemistry and zircon U-Pb geochronology of granite porphyries from the Dabate district with the intent to constrain their tectonic setting and petrogenesis. Porphyries in the Dabate district include granite porphyry I(gray white color with large phenocrysts), granite porphyry II(pink color with small phenocrysts) and quartz porphyry. Granite porphyry II is the Cu and Mo ore-bearing granitoid in the Dabate deposit. LA-ICPMS zircon U-Pb analyses indicate that granite porphyry II was emplaced at 284.2±1.8 Ma. Granite porphyry I and II have similar geochemical features and are both highly fractionated granites:(1) They have high SiO_2 content(70.93–80.18 wt% and 72.14–72.64 wt%, respectively), total alkali(7.58–8.95 wt% and 9.35–9.68 wt%, respectively), mafic index(0.95–0.98 and 0.93–0.94, respectively) and felsic index(0.79–0.94 and 0.89–0.91, respectively);(2) They are characterized by pronounced negative Eu anomaly, "seagullstyle" chondrite-normalized REE patterns and "tetrad effect" of REE;(3) They are rich in Rb, K, Th, Ta, Zr, Hf, Y and REE, but depleted in Sr, P, Ti and Nb. The magma of granite porphyries in Dabate can be interpreted to have been generated by partial melting of the upper crust due to mantle-derived magma underplating in a post-collisional extensional setting.  相似文献   

An extensional and transtensional origin of elongated magmatic domes and localised transfer faults in the northern Menderes metamorphic core complex,western Turkey     

Fuat Erkül  Sibel Tatar Erkül  Hatice Seval Manap  Cihan Çolak 《Geodinamica Acta》2017,29(1):139-159

The northern Menderes metamorphic core complex has complex exhumation history and is one of the key localities to investigate the spatial and temporal relationships of extensional and compressional structures. Detachment faults and syn-extensional plutons are linked to a series of antiforms and synforms and the denudation of the northern Menderes Massif occurred in three stages. The first stage is related to the development of detachment faults under the consistent NE–SW-directed extension. The second stage is represented by a series of elongated magmatic domes that were oriented parallel, oblique and perpendicular to the regional extension direction. Emplacement of these asymmetrical magmatic domes appears to have been controlled by heterogeneous extension and post-dates the extensional Simav detachment fault. On the third stage, progressive heterogeneous extension that led to updoming of plutons has been finally accommodated by a localised and short-lived transfer zone, which was described as the Gerni shear zone for the first time in this study. The transfer zone is formed by a NE-striking, dextral ductile/brittle shear zone that accommodated the propagation of folds, conjugated strike-slip faults and normal- and oblique-slip faults. Mylonites associated with the transfer zone are related to the localisation of strain along the thermally weakened strike-slip fault systems by short-lived intrusions rather than to the development of regional-scale detachment faults. These structures are consistent with a transtensional simple shear model, which properly explains the evolution of extensional and compressional structures exposed in the northern Menderes core complex. Structural setting of the E?rigöz region is somewhat similar to that of the NE-trending gneiss domes in the northern Menderes Massif and updoming of magma during late stages of detachment faulting appears to have played an important role in the exhumation of lower and upper plate rocks.  相似文献   

湘中紫云山岩体的成因:锆石U-Pb年代学、元素地球化学及Hf-O同位素制约   总被引：5，自引：4，他引：1  

鲁玉龙  彭建堂  阳杰华  胡阿香  李玉坤  谭辉跃  肖秋越 《岩石学报》2017,33(6):1705-1728

位于湘中盆地周缘的紫云山岩体主要由似斑状石英二长岩(主体)和二云母花岗岩(补体)组成,前者分布于该岩体的周边,后者分布于其内部,岩体内可见有大量岩浆结构的镁铁质暗色包体。利用高精度SIMS锆石U-Pb定年方法得到主体岩体的年龄为225.2±1.7Ma和225.6±1.4Ma,补体岩体的年龄为227.0±2.2Ma,两者均形成于印支晚期,基本上是同时形成的。该区两类岩石均具有富SiO_2、Na_2O和K_2O,贫Ca O、Mg O和Al2O3的特征,A/CNK比值为0.85~1.05,固结指数较高,主体岩石为3.61~5.05,补体岩石为4.13~14.06;其微量元素均表现出富集Rb、U、La、Nd和Zr,亏损Ba、Nb、Ta、Sr、P和Ti的特征;稀土元素配分模式均呈明显的右倾"V"字型,轻重稀土分馏明显((La/Yb)N=7.35~11.7),Eu负异常较显著(δEu=0.32~0.70);该区花岗岩的主体和补体的锆石Hf-O同位素组成非常相似,εHf(t)值为-10.0~-1.6,δ18O值为7.8~11.4,两阶段模式年龄tDM2为1.22~1.79Ga;各类岩石主要氧化物之间表现出良好的线性协变关系,且明显沿I型花岗岩演化趋势线分布,反映主体和补体岩石具有密切的亲缘关系,均应归属于高分异的I型花岗岩。各类岩石样品沿岩浆混合趋势线分布、而远离结晶分异趋势线,结合Hf-O同位素分析,认为该岩体来源于扬子地块中元古代下地壳变质杂砂岩重熔,与部分幔源岩浆形成的壳幔混合岩浆源区。该岩体形成于碰撞后构造背景,暗示华南地块受太平洋板块及印支地块的双重影响,在印支晚期处于伸展-减薄的构造环境。通过与华南地块其它印支期花岗岩对比分析,提出扬子地块与华夏地块的拼合带在湖南境内应沿"攸县-双牌"一线展布。  相似文献   

A crustal source for ca. 165 Ma post-collisional granites related to mineralization in the Jianglang dome of the Songpan-Ganzi Orogen,eastern Tiebtan Plateau     

《Chemie der Erde / Geochemistry》2017,77(4):573-586

The Wenjiaping and Wulaxi granite plutons are located in the Jianglang dome, which is a key domain for providing deep insight into the tectonic evolution of the Songpan-Ganzi Orogen. Two granites are composed chiefly of K-feldspar, quartz, biotite with minor plagioclase and hornblende. This study presents zircon U-Pb chronology, geochemistry and Hf isotope data to explore their petrogenesis and metallogenic implications. Zircon U-Pb dating provides crystallization ages of 164.5 ± 0.9 Ma and 163.4 ± 0.9 Ma for the Wenjiaping granite, and 164.3 ± 1.7 Ma for the Wulaxi granite. This indicates that they were formed synchronously. They also contain inherited zircons related to the Rodinia and Gondwana supercontinents and the Emeishan large igneous province. Their mineral assemblages lack peraluminous (e.g., garnet and cordierite) and high-temperature (e.g., pyroxene and fayalite) minerals. They are characterized by low A/CNK (1.10–0.99), FeO^T/MgO (8.55–2.83) and K₂O/N₂O ratios (1.34–0.51) with low Zr + Nb + Ce + Y concentrations (average 258 ppm) and zircon saturation temperatures (781–651 °C). Their Al₂O₃, P₂O₅ and SiO₂ contents show negative correlations, and they thus fit the I-type granite definition. Some major and trace elements exhibit strong correlations, implying extensive fractional crystallization (e.g., hornblende and ilmenite) during the magma evolution. Two granites show enrichment in light rare earth elements and large ion lithophile elements, and depletion in high field strength elements. They have low Mg^# values (38.7–17.3) and Y/Nb ratios (0.45–0.16), and yield dominantly negative ε_Hf(t) values (1.4–−13.9), indicating a heterogeneous source and their derivation from remelting of ancient continental crust (e.g., Mesoproterozoic Liwu Group in this region) with minor juvenile crust. Combined with prior studies, we conclude that the Wenjiaping and Wulaxi granites were formed in a post-collisional extensional regime, and were responsible for the 163.7–151.1 Ma magmatic hydrothermal Cu-W mineralization in the Jianglang dome. In addition, two granite plutons intrude this dome and they are undeformed, implying that the doming was during the Early to Middle Jurassic.  相似文献   

基于熵权的可拓理论在岩体质量评价中的应用   总被引：10，自引：0，他引：10  

梁桂兰  徐卫亚  谈小龙 《岩土力学》2010,31(2):535-540

坝基岩体质量综合评价是一个复杂的工程决策问题,常常表现为指标与指标之间的矛盾、定性信息与定量信息的共存,解决这类多属性、不相容问题,应采用定性与定量综合集成的方法加以研究。而可拓学正是采用物元的概念将研究对象、评估指标与其值域结合为一体,研究事物可拓性及其开拓规律,解决矛盾问题的一门新学科。应用可拓理论,基于多指标优化融合的思想,通过物元变换建立了坝基岩体质量评价的物元体系,计算评价指标对评价等级的关联系数,引入熵权法确定物元指标体系的权重系数,建立了基于熵权的可拓学理论,并将此理论应用于某工程坝基岩体质量评价,取得了与工程地质报告相一致的评价结果。  相似文献   

盐岩储气库运营期稳定性评价研究   总被引：4，自引：1，他引：3  

任松  李小勇  姜德义  王新胜  杨春和 《岩土力学》2011,32(5):1465-1472

针对国内盐岩矿床的特点,建立了盐岩地下储气库运营期稳定性的多层次、多指标综合评价体系,并定义了盐岩地下储气库运营期稳定性等级标准。根据试验数据和数值模拟结果,构建了各评价指标的评分模型,得出了各评价等级相应评价指标的量值。采用AHP方法分析得到了描述层和指标层参数的权重。分别应用可拓法和模糊综合评价法对西气东输工程金坛储气库西1库进行运营期稳定性评价,两种方法评价结果一致,并与实际情况吻合,表明建立的盐岩地下储气库运营期稳定性的多层次、多指标综合评价体系能客观反应储库的实际稳定情况,具有较高的推广价值  相似文献   

基于综合权重和改进物元可拓评价模型的地下水水质评价   总被引：2，自引：0，他引：2  

虞未江  贾超  狄胜同  李康  袁涵 《吉林大学学报(地球科学版)》2019,49(2):539-547

鉴于物元可拓评价模型存在关联函数计算上的局限性,提出通过改进物元可拓评价模型的构造过程进行水质评价,并引入层次分析法和熵权法计算评价指标的综合权重以避免指标权重的绝对主观性和绝对客观性,建立了基于综合权重和改进物元可拓法的地下水水质评价模型,并从感官、一般化学、毒理学3个方面构建了地下水水质综合评价指标体系。将该模型应用于平度市古岘镇的地下水水质评价,并与综合评分法和属性识别法的水质评价结果进行比较分析。结果表明：该模型评价结果与其他两种方法评价结果的相同率均达70%,即使评价结果不同处的差异也基本在1个等级范围之内;而综合评分法和属性识别法评价结果的相同率仅为50%,且评价结果不同处的差异最大可达3个等级。  相似文献   

基于MySQL空间扩展的GIS开发技术研究     

杜锦华  邹峥嵘  刘平 《地理信息世界》2012,10(3):62-67

MySQL遵从了OpenGIS联盟的规范实施了空间扩展,定义了自己的空间数据类型和相应的操作函数,从而在MySQL中允许生成、保存和分析地理要素以及用于GIS开发。本文介绍了OpenGIS空间模型、MySQL空间扩展的具体细节和MySQL C API主要函数,并将这些理论应用于实例程序的MySQL实现中,实例程序采用C+Win32 API+MySQL C API相结合的方法实现。通过实例程序简单介绍了基于C语言开发GIS程序的一般步骤。  相似文献   

银川盆地不同构造层构造样式及形成演化分析   总被引：2，自引：0，他引：2  

侯旭波  崔红庄  郇玉龙 《东北石油大学学报》2012,(6):28-33,7

为研究银川盆地构造样式及形成演化,以地震资料的精细解析为基础,分析构造样式类型和发育特征,并结合区域地质背景从断裂控盆方面分析其演化过程.结果表明:银川盆地经历中生代挤压隆升剥蚀和新生代伸展断陷2个主要演化阶段,共发育4类构造样式,其中新生界构造层以伸展和伸展—走滑构造样式为主,基底构造层以挤压和反转构造样式为主.该研究结果对明确银川盆地地质结构及油气勘探具有指导意义.  相似文献