嫩江科洛地区晚侏罗世深熔花岗岩对嫩江-黑河构造带的响应          下载免费PDF全文

杨晓平  汪岩  杨超  谭红艳 《中国地质调查》2018,5(3):36-42

通过对嫩江-黑河构造带内的岩石建造研究,在嫩江科洛地区识别出一套深熔花岗岩体,岩石宏观上为一套具非典型花岗岩结构的深熔型侵入岩,具交代结构、斑杂状构造和眼球状构造。对深熔花岗岩进行了锆石LA-ICP-MS U-Pb年龄测试,获得了3组不谐和的U-Pb年龄: 390 Ma、157~163 Ma和113 Ma。其中,113 Ma年龄代表了岩石遭受后期变质热事件年龄; 157~163 Ma的年龄代表了原岩结晶年龄。综合分析深熔花岗岩成因,认为其主要与嫩江-黑河断裂深部韧性剪切热效应作用下发生的深熔有关,深熔花岗岩的划分和厘定为深入研究嫩江-黑河断裂带在中生代的活动提供了新的素材。  相似文献   

Origin of abundant moonmilk deposits in a subsurface granitic environment     

《Sedimentology》2018,65(5):1482-1503

Subsurface granitic environments are scarce and poorly investigated. A multi‐disciplinary approach was used to characterize the abundant moonmilk deposits and associated microbial communities coating the granite walls of the 16th Century Paranhos spring water tunnel in Porto city (north‐west Portugal). It is possible that this study is the first record of moonmilk in an urban subsurface granitic environment. The morphology and texture, mineralogical composition, stable isotope composition and microbial diversity of moonmilk deposits have been studied to infer the processes of moonmilk formation. These whitish secondary mineral deposits are composed of very fine needle‐fibre calcite crystals with different morphologies and density. Calcified filaments of fungal hyphae or bacteria were distinguished by field emission scanning electron microscopy. Stable isotope analysis revealed a meteoric origin of the needle‐fibre calcite, with an important contribution of atmospheric CO ₂, soil respiration and from weathering of Ca‐bearing minerals. The DNA ‐based analyses revealed the presence of micro‐organisms related to urban contamination, including Actinobacteria, mainly represented by Pseudonocardia hispaniensis , Thaumarchaeota and Ascomycota, dominated by Cladosporium . This microbial composition is consistent with groundwater pollution and contamination sources of the overlying urban area, including garages, petrol stations and wastewater pipeline leakage, showing that the Paranhos tunnel is greatly perturbed by anthropogenic activities. Whether the identified micro‐organisms are involved in the formation of the needle‐fibre calcite or not is difficult to demonstrate, but this study evidenced both abiotic and biogenic genesis for the calcite moonmilk in this subsurface granitic environment.  相似文献   

Study of late-Mesozoic magmatic rocks and their related copper-gold-polymetallic deposits in the Guichi ore-cluster district,Lower Yangtze River Metallogenic Belt,East China     

Huangling Gu  Zhangxing Nie  Jianghong Deng  Liuan Duan  Qing Hu 《International Geology Review》2018,60(11-14):1404-1434

ABSTRACT

The Guichi ore-cluster district in the Lower Yangtze River Metallogenic Belt hosts extensive Cu–Au–Mo polymetallic deposits including the Tongshan Cu–Mo, Paodaoling Au, Matou Cu–Mo, Anzishan Cu–Mo, Guilinzheng Mo and Zhaceqiao Au deposits, mostly associated with the late Mesozoic magmatic rocks, which has been drawn to attention of study and exploration. However, the metallogenic relationship between magmatic rocks and the Cu–Au-polymetallic deposits is not well constrained. In this study, we report new zircon U–Pb ages, Hf isotopic, and geochemical data for the ore-bearing intrusions of Guichi region. LA-ICP-MS U–Pb ages for the Anzishan quartz diorite porphyrite is 143.9 ± 1.0 Ma. Integrated with previous geochronological data, these late Mesozoic magmatic rocks can be subdivided into two stages of magmatic activities. The first stage (150–132 Ma) is characterized by high-K calc-alkaline intrusions closely associated with Cu–Au polymetallic ore deposits. Whereas, the second stage (130–125 Ma) produced granites and syenites and is mainly characterized by shoshonite series that are related to Mo–Cu mineralization. The first stage of magmatic rocks is considered to be formed by partial melting of subducted Palaeo-Pacific Plate, assimilated with Yangtze lower crust and remelting Meso-Neoproterozoic crust/sediments. The second stage of magmatism is originated from partial melting of Mesoproterozoic-Neoproterozoic crust, mixed with juvenile crustal materials. The depression cross to the uplift zone of the Jiangnan Ancient Continent forms a gradual transition relation, and the hydrothermal mineralization composite with two stages have certain characteristics along the regional fault (Gaotan Fault). Guichi region results from two episodes of magmatism probably related to tectonic transition from subduction of Palaeo-Pacific Plate to back-arc extensional setting between 150 and 125 Ma, which lead to the Mesozoic large-scale polymetallic mineralization events in southeast China.  相似文献   

福建霞浦大湾钼铍矿区碱长花岗岩LA-ICP-MS锆石U-Pb测年研究   总被引：2，自引：1，他引：1  

黄新鹏 《岩矿测试》2018,37(5):572-579

福建霞浦大湾钼铍矿床产于火山岩区,但成矿作用可能与岩浆活动和裂隙构造关系密切。为查清矿区隐伏的钠长石化碱长花岗岩与钼铍矿成矿作用之间的关系,本文运用激光剥蚀电感耦合等离子体质谱法(LA-ICP-MS)对碱长花岗岩进行锆石U-Pb测年研究,获得年龄结果为93. 0±0. 6 Ma,与矿区的辉钼矿成矿年龄(92. 2±1. 3 Ma)一致,表明碱长花岗岩与钼铍矿成矿作用时空上具有密切的成因联系,岩浆活动可能为矿区钼铍矿的形成提供了成矿物质和成矿流体。结合区域上的成岩成矿年代学数据,本研究认为福建省燕山期岩浆活动时代与钼铍矿成矿时代都具有从西向东逐渐变新的时空分布规律,钼铍矿的成矿地质构造背景为燕山期华南岩石圈伸展环境。  相似文献   

辽东半岛大金山花岗岩体SHRIMP U-Pb年龄、元素地球化学和Hf同位素特征及地质意义     

杨佳林  顾玉超  杨凤超  李东涛  鞠楠  贾宏翔 《地质论评》2018,64(6):1541-1556

辽东半岛早白垩世时期受到强烈的构造—岩浆作用使岩石圈构造环境由挤压造山向伸展减薄转变,前人对其成因有所争议。本文通过锆石SHRIMP U- Pb测年、原位Lu- Hf同位素和主量、微量、稀土元素测试对辽东半岛大金山花岗岩体进行了系统研究,结果显示：大金山花岗岩体结晶年龄为~ 124Ma,侵位于早白垩世岩浆活动的高峰期。岩石地球化学特征显示大金山花岗岩属弱过铝质~过铝质岩石,经历了高程度的结晶分异过程,富集Rb、Th、U、K等大离子亲石元素（LILE）,亏损P、Ti等高场强元素（HFSE）,中等Eu负异常,为I型花岗岩。TW003样品εHf(t)值为-25.8~ -14.2,tDM2为2093~2805Ma,岩浆物质来源于新太古代—古元古代下地壳火成岩的部分熔融。根据年代学和岩石地球化学研究认为大金山花岗岩是古太平洋板块向欧亚大陆板块俯冲所形成的活动大陆边缘弧花岗岩,辽东半岛早白垩世的伸展环境是受板块俯冲造山后伸展作用和下地壳拆沉作用的联合制约。  相似文献   

川西扎乌龙花岗伟晶岩型稀有金属矿床白云母花岗岩岩石地球化学特征   总被引：8，自引：0，他引：8  

李兴杰  李建康  刘永超  熊昌利 《地质论评》2018,64(4):1005-1016

扎乌龙花岗伟晶岩型稀有金属矿床位于四川西部石渠县呷依乡,矿区出露的白云母花岗岩岩体与含稀有金属伟晶岩脉有密切的时空关系及成因联系。本文对采自扎乌龙白云母花岗岩岩体的新鲜样品进行了全岩岩石地球化学分析,结果表明,该岩体岩石富硅(Si O_2=73.49%~74.78%)、富铝(Al_2O_3=14.37%~14.83%)、高钾(K_2O/Na_2O=1.14~1.91),贫Fe、Mg、Ti,里特曼指数(σ)3.3,铝饱和指数和Al_2O_3/Ti O_2(100)较高。以上特征表明该岩体属高压型高钾钙碱性强过铝质花岗岩。微量元素表现出Rb、U等正异常和Ba、Sr、Zr、Ti等负异常的特征;岩石稀土总量较低,具有明显的轻稀土富集,重稀土亏损的特征,且由于较明显的负铕异常(δEu=0.36~0.53)而呈现"V"型谷状。岩石高Rb/Sr(2.08~6.51)和Rb/Ba(1.53~3.26)、低Ca O/Na_2O(0.3)等地球化学特征,表明其来源于三叠系西康群泥质岩的脱水熔融,是同碰撞造山作用的产物。而扎乌龙式LCT型花岗伟晶岩,主要是由造山过程中变泥质岩部分熔融形成的强过铝质岩浆逐步演化而形成。  相似文献   

华北地台北缘集宁地区古元古代片麻状石榴花岗岩的深熔成因及地质意义   总被引：3，自引：3，他引：0  

石强  董晓杰  徐仲元  关庆彬  李鹏川  张超  崔芳华 《岩石学报》2018,34(9):2754-2772

本文对华北克拉通北缘集宁地区空间上密切共生的片麻状石榴花岗岩和孔兹岩系富铝片麻岩的岩相学、地球化学及年代学特征进行了对比研究。SHRIMP锆石U-Pb定年方面,在富铝片麻岩中获得了1910±10Ma和1839±13Ma变质锆石年龄,在片麻状石榴花岗岩中获得了1919±17Ma的变质重结晶锆石年龄。在石榴花岗岩的石榴石包裹体中识别出与富铝片麻岩相对应的进变质阶段(M1)和峰期阶段(M2)的矿物组合,由此确认富铝片麻岩的变质作用和导致石榴花岗岩形成的深熔作用是同一构造热事件的产物。通过对二者变质作用演化及特征变质矿物的对比,认为深熔作用主要发生在峰期后等温降压阶段(M3),石榴花岗岩中的石榴石为深熔作用过程中的残留矿物相或转熔矿物相,而石榴花岗岩则是混合有大量残留矿物相的熔体结晶的产物。对片麻状石榴花岗岩和富铝片麻岩的地球化学组成特征进行了对比分析,片麻状石榴花岗岩既有一定的继承性,又有十分明显的变异性。变异性表现为:1)石榴花岗岩主量和微量元素含量分布极不均匀,微量元素含量普遍低于源岩(Cs、Rb、Th、U、Nb、Ta、Zr、Hf等);2)大离子亲石元素Cs和生热元素U、Th亏损明显,Sr相对富集;3)高场强元素Nb、Ta、P、Ti的明显亏损;4)铕异常变化大,存在铕富集型、铕平坦型和铕亏损型共存的稀土配分曲线的岩石,这是深熔成因石榴花岗岩最突出的表现,也可能是原地-半原地深熔花岗岩的主要地球化学标志。综合区域上的地质资料,认为深熔作用与碰撞后伸展构造背景下基性岩浆底侵事件有关。  相似文献   

张广才岭南段两个侏罗纪花岗岩体的地球化学特征及其地质意义     

句高  梁一鸿  孙晓  周静 《世界地质》2018,37(2):374-384

通过LA-ICP-MS锆石U-Pb定年和岩石化学分析,研究了张广才岭南段上营北岩体和帽儿山岩体的形成年代,地球化学特征和形成环境。上营北岩体为中粗粒钾长花岗岩,帽儿山岩体为中细粒黑云母钾长花岗岩。上营北岩体的加权平均年龄为178.9±2.7 Ma,帽儿山岩体为183.7±2.4 Ma,均为早侏罗世侵入岩。上营北岩体和帽儿山岩体主量元素都具有Si O_2和K_2O含量较高,Ti O_2、Mg O、Ca O含量较低,TFe O/Mg O值较高的特点;上营北岩体A/CNK=0.98~1.08,里特曼指数σ=1.51~2.66;帽儿山岩体含铝指数A/CNK=1.00~1.01,里特曼指数σ=2.12~2.36。上营北岩体稀土元素配分模式为海鸥型,轻重稀土分馏不明显;帽儿山岩体稀土元素配分模式为右倾型,轻稀土较重稀土富集;两个岩体均富集Rb、K,Ba、Nb、Ta、Sr、Ti、P、Ho、Er、U、Eu等元素出现不同程度的亏损。地球化学特征分析显示上营北岩体和帽儿山岩体均为A_2型花岗岩,为后造山型花岗岩,形成于兴蒙造山带后造山的伸展环境。  相似文献   

花岗岩定量分类方法及与成矿空间相关关系分析 ——甘肃省西秦岭地区为例          下载免费PDF全文

王晓伟  罗建民  王玉玺  张琪  宋秉田  杨忠明  赵彦庆 《甘肃地质》2018,(1):26-31

以Q型系统聚类分析(以组内连接为聚类方法,相关性为计算模型)和判别分析交替使用的方法,对甘肃省西秦岭地区花岗岩样本中的11个氧化物测试数据进行定量处理,构建起"甘肃省西秦岭地区花岗岩(氧化物)定量分类系列模型",将西秦岭地区花岗岩分为3大类共8小类。分类结果偏重于找矿分类,依据其与西秦岭地区铜矿、铅锌矿、金矿等依据空间关系(距离岩体3 km以内),寻找"成矿相关岩体",确定找矿靶区。  相似文献   

内蒙古阿拉善右旗大山口地区黑云母花岗岩地球化学特征及成因          下载免费PDF全文

李伟  赵飞  熊文勃  李延涛  黄瀚清 《甘肃地质》2018,(2):29-35

内蒙古自治区阿拉善右旗大山口地区发育有大面积侵入岩,主要为华力西中晚期和印支期酸性侵入岩体及各类脉岩。本次运用LA-ICP-MS锆石U-Pb测年方法获得黑云母花岗岩的成岩年龄为229.5±5.6 Ma,属晚三叠世,大山口黑云母花岗岩SiO_2含量68.89%～71.04%,相对富钾贫钠;A/NKC介于0.89～1.05,强烈富集强不相容元素,亏损高场强元素Na、Ta、Ti、P,Eu异常不明显,HREE呈近平坦型分布。通过黑云母花岗岩的成因研究和构造环境判别分析,认为大山口黑云母花岗岩为加厚的中下地壳物质拆沉进入地幔加热并发生部分熔融,且熔体可能与地幔基性熔体发生一定程度的混合作用后上升形成的花岗岩,形成于晚三叠世后碰撞伸展垮塌的构造环境。  相似文献