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91.
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
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
92.
海南岛北西部前寒武纪花岗质岩SHRIMP锆石U-Pb年龄及地质意义 总被引:11,自引:4,他引:7
对海南岛北西部戈枕地区侵位于古中元古代抱板群花岗质岩进行了CL成像制约下的SHRIMP锆石U-Pb年龄测定,获得了1455±12Ma的U-Pb谐和年龄、1454±12Ma有利的207Pb/206Pb中值年龄。结合该花岗质岩锆石内部结构、岩浆源区和变形变质特征,以及前人多种定年成果,认为该花岗质岩结晶年龄应为~1450Ma,随后于~1400Ma经历了一次构造-热变质事件;Rodinia超大陆聚合前,华夏地块(包括海南岛、或至少是海南岛北西部)最可能位于劳伦大陆南缘的西南延伸部分。研究结果还暗示华夏地块(包括海南岛)所经历的格林威尔造山事件可能较扬子地块偏早,古、中元古代抱板群沉积上限应约束在~1450Ma。 相似文献
93.
The Indosinian Orogeny plays a significant role in tectonic background and magmatic evolution in Indochina and surrounding regions. Being a part product of the Indosinian magmatism in northwest Vietnam during late Permian–middle Triassic period, Muong Luan granitoid pluton dominantly consists of granodiorite, less diorite and granite. This pluton is located in the Song Ma suture and assigned to the Dien Bien complex. Geochemically, the Muong Luan granitoid rocks are characterized by a wide range of SiO2 contents (59.9–75.1 wt%) and high K2O contents. They display typical features of I‐type granites. The presence of hornblende and no muscovite and cordierite in the rocks further supports for I‐type character of granitoids. The emplacement age of the Muong Luan pluton obtained by LA–ICP–MS U–Pb zircon is at 242–235 Ma, corresponding to Indosinian time. Zircon εHf values of –5.6 to –10.4, in combination with moderate Mg values of 34–45 suggested that the Muong Luan granitoid was derived from partial melting of mafic crustal source rocks, which are probably Paleoproterozoic in age as revealed by Hf model ages (TDM2 = 1624–1923 Ma). 相似文献
94.
Asma Nazarinia Mohsen Arvin Ruizhong Hu Chenghai Zhao Mohammad Poosti 《International Geology Review》2020,62(13-14):1796-1814
ABSTRACT The Sarduiyeh granitoid (SG) is intruded in the southeastern part of the Dehaj-Sarduiyeh volcano-sedimentary belt in the southeastern end of the Urumieh-Dokhtar Magmatic Arc (UDMA) in Iran. The medium-to-coarse-grained granitoid unit, with granular texture consists mainly of diorite, tonalite, granodiorite and monzogranitic rocks. Mineralogically, these rocks consist mainly of plagioclase, K-feldspar, quartz, biotite and hornblende. The whole rock geochemical analyses indicates that the SG is calc-alkaline, I-type, metaluminous, enriched in large ion lithophile elements (LILE; such as K, Cs, Pb) and depleted in high field strength elements (HFSE; such as Ti, Nb, Ta, Zr). Chondrite normalized plot of SG rare earth elements (REE) show light rare earth element enrichments with (LaN/YbN = 2.44–8.68) and flat heavy rare earth element patterns with (GdN/YbN = 1.02–1.36). The rather high Y (av. 19.35 ppm), low Sr content (av. 293.76 ppm) and low Cr and Ni contents (av. 20.1 and 4.69 ppm, respectively) of the SG demonstrate its normal calc-alkaline and non-adakitic nature, the features of Jebal Barez-type granitoids. The geochemical characteristics and isotopic composition, low ISr (0.7046–0.7049) and positive ?tNd (+3.4 to +4.03) values, of the SG suggest that its parental magma formed as a result of partial melting from metabasic rocks of lower crust in a subduction-related arc setting. Fractionation of an assemblage dominated by plagioclase, K-feldspar, amphibole and magnetite may have been responsible for the evolution of the SG magma. U-Pb zircon geochronology gives an age of 27.95 ± 0.27 Ma for the SG, suggesting that the final collision between the Arabian plate and Central Iranian microcontinent may have happened in the Late Oligocene. 相似文献
95.
试论花岗质深成岩体的复合定位机制及定位空间问题 总被引:12,自引:0,他引:12
大陆地壳中巨量花岗岩体的定位机制及定位空间是一个长期急论的问题,已提出十余种机制,但都困难以解决定位空间面引起争议,近年来,人们认识到岩体定位及获取空间是多种机制共存的复合定位机制,这是今后需进一步研究的新课题,笔者提出的复合定位机制可概括为主动膨胀,构造扩展,岩浆侵吞作用3个基本端元机制的构成的复合,可用三角图解表述,并以具体研究实例进行了论述。 相似文献
96.
YANG Pengtao LIU Shuwen LI Qiugen ZHANG Fan WANG Zongqi WANG Dongsheng WANG Ruiting YAN Quanren YAN Zhen 《《地质学报》英文版》2011,85(4):854-869
The Laocheng granitoid pluton is located in the South Qinling tectonic domain of the Qinling orogenic belt,southern Shaanxi Province,and consists chiefly of quartz diorite,granodiorite and monzogranite.A LA-ICP-MS zircon U-Pb isotopic dating,in conjunction with cathodoluminescence images,reveals that the quartz diorite and granodiorite were emplaced from 220 Ma to 216 Ma,while the monzogranite was emplaced at~210 Ma.In-situ zircon Hf isotopic analyses show that theε_(Hf)(t) values of the quartz diorite a... 相似文献
97.
98.
刘家堡子超单元同位素锆石U- Pb 一致线年龄值为2 046.48±7 .01Ma,侵位时代为古元古代。按照侵入岩岩石谱系单位的划分原则,由早至晚划分为红旗村单元石英闪长岩、头道阳岔单元花岗闪长岩及阳隈子单元二长花岗岩,归并为刘家堡子超单元。成因类型为Ⅰ型花岗岩类,成岩物质来源于下地壳,岩浆演化由中性至酸性,演化明显,构成了完整的演化序列。 相似文献
99.
100.
《International Geology Review》2012,54(16):1885-1905
Late Mesozoic granitoid plutons of four distinct ages intrude the lower plate of the Hohhot metamorphic core complex along the northern margin of the North China craton. The plutons belong to two main groups: (1) Group I, deformed granitoids (148 and 140 Ma subgroups) with high Sr, LREE, and Na2O, low Y and Yb contents, high Sr/Y and La/Yb ratios, weak or no Eu anomalies, low Rb/Ba ratios, similar initial 87Sr/86Sr values (0.7064–0.7071) and low Mg# (<37 mostly, 100?×?molar MgO/MgO + FeO t ); (2) Group II, non-deformed granitoids (132 and 114 Ma subgroups) with low Sr, relatively low Na2O, high Y and Yb contents, pronounced negative Eu anomalies, high Rb/Ba ratios, and initial 87Sr/86Sr values (0.7098–0.7161). The two groups share geochemical similarities in ?Nd(t) (–11.3 to –15.4) and T DM2 ages (1.85–2.18 thousand million years) as well as Hf isotopic ratios in zircons. Geochemical modelling (using the MELTS code) suggests that similar sources but different depths of magma generation produced the early, high-pressure low-Mg adakitic granitoids and late, low-pressure granitoids with A-type characteristics. The early granitoids likely represent a partially melted, deep-seated, thickened lower continental crust that involved a minor contribution from young materials, whereas the later group partially melted at shallower depths. This granitic magmatic evolution coincided with the tectonic transition from crustal contraction to extension. 相似文献