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   

湖北渔塘坝硒矿床中次生自然硒的特征与意义   总被引：1，自引：0，他引：1  

刘家军  冯彩霞  李志明  王建平  刘世荣  周国富 《现代地质》2005,19(4):531-537

在湖北渔塘坝硒矿床氧化矿石及地表松散堆积物中存在大量罕见的次生自然硒。自然硒呈柱状、板状和它形粒状。它的形成一方面与硒矿石的风化作用有关,另一方面系当地居民用石煤烧石灰过程中导致硒的蒸发而发生次生富集的结果。矿床中大量次生自然硒的发现,不仅对硒的矿物学、矿床地球化学、环境地球化学研究具有重要价值,而且对解决或改进含碳硒矿石或岩石中硒的冶炼回收工艺流程具有一定的启迪意义。  相似文献   

Mercury and methylmercury in riparian soil,sediments, mine-waste calcines,and moss from abandoned Hg mines in east Guizhou province,southwestern China     

《Applied Geochemistry》2005,20(3):627-638

Concentrations of total Hg and methylmercury (MMHg) in riparian soil, mine-waste calcine, sediment, and moss samples collected from abandoned Hg mines in Wanshan district, Guizhou province, China, were measured to show regional dispersion of Hg-contamination. High total Hg and MMHg concentrations obtained in riparian soils from mined areas, ranged from 5.1 to 790 mg kg⁻¹ and 0.13 to 15 ng g⁻¹, respectively. However, total Hg and MMHg concentrations in the soils collected from control sites were significantly lower varying from 0.1 to 1.2 mg kg⁻¹ and 0.10 to 1.6 ng g⁻¹, respectively. Total Hg and MMHg concentrations in sediments varied from 90 to 930 mg kg⁻¹ and 3.0 to 20 ng g⁻¹, respectively. Total Hg concentrations in mine-waste calcines were highly elevated ranging from 5.7 to 4400 mg kg⁻¹, but MMHg concentrations were generally low ranging from 0.17 to 1.1 ng g⁻¹. Similar to the high Hg concentrations in soil and sediments, moss samples collected from rocks ranged from 1.0 to 95 mg kg⁻¹ in total Hg and from 0.21 to 20 ng g⁻¹ in MMHg. Elevated Hg concentrations in mosses suggest that atmospheric deposition might be an important pathway of Hg to the local terrestrial system. Moreover, the spatial distribution patterns of Hg contamination in the local environment suggest derivation from historic Hg mining sites in the Wanshan area.  相似文献   

Geochronology of layered mafic intrusions from the Pan–Xi area in the Emeishan large igneous province, SW China     

Hong Zhong  Wei-Guang Zhu 《Mineralium Deposita》2006,41(6):599-606

The Panzhihua–Xichang (Pan-Xi) area hosts mafic/ultramafic intrusions, which are part of the Permian Emeishan large igneous province. Some of these intrusions host giant Fe–Ti–V deposits and minor Ni–Cu–PGE mineralization. In the present study, zircon U–Pb ages of 259.3±1.3 and 260.7±0.8 Ma have been obtained from the giant Fe–Ti–V ore-bearing Hongge and the unmineralized Binggu intrusions, respectively, by isotope dilution thermal ionization mass spectrometry method. In combination with the ages of other ore-bearing intrusions, this age shows that these mafic/ultramafic intrusions were emplaced at ca. 260 Ma. The Hongge and Binggu intrusions cut the lower part of the rapidly deposited Emeishan flood basalt sequence but no further into the upper volcanic sequence in the Pan-Xi area. Thus, emplacement and mineralization of the mafic/ultramafic intrusions were almost contemporaneous with the eruption of the Emeishan flood basalts during a relatively short time span.  相似文献   

Precise molybdenite Re–Os and mica Ar–Ar dating of the Mesozoic Yaogangxian tungsten deposit, central Nanling district, South China     

Jiantang Peng  Mei-Fu Zhou  Ruizhong Hu  Nengping Shen  Shunda Yuan  Xianwu Bi  Andao Du  Wenjun Qu 《Mineralium Deposita》2006,41(7):661-669

The Yaogangxian deposit in the central Nanling region, South China consists of vein-type ore bodies hosted in Cambrian to Jurassic strata and Mesozoic granitic intrusions. Wolframite and molybdenite are the dominant ore minerals intergrown with gangue minerals of quartz, feldspar, phlogopite, and muscovite. We have carried out molybdenite Re–Os and phlogopite and muscovite ⁴⁰Ar/³⁹Ar dating to better understand the timing and genesis of mineralization. Re–Os dating of eight molybdenite samples yielded model ages ranging from 152.0±3.5 to 161.1±4.5 Ma, with an average of 156.0 Ma. The Re–Os analyses give a well-defined ¹⁸⁷Re/¹⁸⁷Os isochron with an age of 154.9±2.6 Ma (MSWD=2.4). Hydrothermal phlogopite and muscovite display extremely flat ⁴⁰Ar/³⁹Ar age spectra. Phlogopite yields a ⁴⁰Ar/³⁹Ar plateau age of 153.0±1.1 Ma, whereas muscovite yields a plateau age of 155.1±1.1 Ma. Both ⁴⁰Ar/³⁹Ar ages are in good agreement with the Re–Os ages, placing the timing of tungsten mineralization at about 154 Ma. This age is consistent with the field relationships. Our new data, when combined with published geochronological results from other major deposits in this region, suggest that large scale W–Sn mineralization occurred throughout the central Nanling region in the Late Jurassic.  相似文献   

京北云蒙山变质核杂岩南东侧剥离断层带的构造热演化   总被引：4，自引：0，他引：4  

王巧云  颜丹平  苏本勋  周密  胡瑞忠 《地质通报》2006,25(4):448-453

以云蒙山变质核杂岩东侧的河防口低角度正断层为研究对象,通过矿物(黑云母)的变形特征和形成环境分析,获得了该断层带上的构造热演化环境:温度为780～860℃,压力约为7.3×108～8.6×108Pa.提出云蒙山变质核杂岩的成因机制是,在区域伸展背景下,处于半固结状态的云蒙山花岗岩在东南侧卷入河防口-水峪伸展型韧性剪切带,使花岗岩发生中高温条件的韧性变形;之后,该韧性剪切带在隆升过程中不断向浅层次过渡,形成了一些浅层次的脆性伸展变形构造.  相似文献   

Hydrothermal venting and basin evolution (Devonian,South China): Constraints from rare earth element geochemistry of chert     

《Sedimentary Geology》2006,183(3-4):203-216

This paper presents rare earth element (REE) geochemistry of siliceous deposits from which hydrothermal activity and basin evolution are elucidated, in the Late Devonian, in the Yangshuo basin, South China, where siliceous deposits widely occurred as nodular chert in the deep-water limestones and bedded chert interbeded with tuffaceous chert in the early Late Devonian. Both nodular and bedded cherts are characterized by very low La abundances (avg. 2.07 and 2.49 ppm, respectively), intermediate negative Ce anomalies (Ce/Ce*: avg. 0. 69 and 0.61), slight to intermediate positive Eu anomalies (Eu/Eu*: avg. 1.33 and 1.57), and low to intermediate shale-normalized La_n/Yb_n values (avg. 0.86 and 0.52) and intermediate La_n/Ce_n values (avg. 1.61 and 1.72). These suggest both nodular and bedded cherts formed in the open marine basin of South China, rather than in the intracontinental rift basin as previously assumed, with involvement both with seawaters as indicated by intermediate negative Ce anomalies and generally LREE-depleted patterns, and hydrothermal vent fluids as indicated by convex, less LREE-depleted patterns with apparent positive Eu anomalies. In comparison with nodular and bedded chert, the tuffaceous chert has the highest La abundances (avg. 17.11 ppm), similar ranges of Ce anomalies (avg. 0.63) and La_n/Ce_n values (avg. 1.77), but lower La_n/Yb_n values (avg. 0.48) and no apparent positive Eu anomalies (avg. 0.97). This suggests that the tuffaceous fallouts were also significantly modified by the hydrothermal fluid and seawater. Rapid spatial variations of Eu/Eu* values and degree of LREE-depletions in the studied basin are recognized, characterizing a spatially differential hydothermal activity that is not well discriminated by major element features. Such a difference in hydrothermal activity is interpreted as having been related to the intensity and depth of syndepositional tectonic activity, reconciling the structural pattern unraveled by stratigraphic packages.  相似文献   

湖北徐家山锑矿床方解石C、O、Sr同位素地球化学   总被引：4，自引：0，他引：4  

沈能平  彭建堂  袁顺达  张东亮  符亚洲  胡瑞忠 《地球化学》2007,36(5):479-485

湖北通山的徐家山锑矿床产在上震旦统陡山沱组和灯影组的海相碳酸盐岩中.对该矿床中成矿前和成矿期方解石进行了较系统的C、O、Sr同位素地球化学研究,结果表明,成矿前方解石具相对较高的δ13CPDB(-0.7‰～ 2.0‰)、δ18OSMOW( 18.6‰～ 19.6‰)和Sr含量(2645-8174 μg/g,平均5656μg/g),及较低的87Sr/86Sr比值(0.7096～0.7097);而成矿期方解石具相对较低的δ13CPDB(-3.9‰～-2.1‰)、δ18OSMOW( 11.5‰～ 15.3‰)、Sr含量(785～2563μg/g,平均1571μg/g),和较高的87Sr/86Sr比值(O.7109～0.7154,平均0.7141).分析认为,成矿前方解石的C、O和绝大部分Sr来源于赋矿围岩--震旦系海相碳酸盐岩;而成矿流体为富H2CO3的溶液,它来自或流经富放射成因87Sr的下伏基底碎屑岩--中元古界冷家溪群浅变质岩;该流体与围岩发生水.岩反应导致成矿期方解石和辉锑矿的沉淀.  相似文献   

湖南芙蓉锡矿床⁴⁰Ar/³⁹Ar 同位素年龄及地质意义   总被引：28，自引：3，他引：28  

彭建堂  胡瑞忠  毕献武  戴橦谟  李兆丽  李晓敏  双燕  袁顺达  刘世荣 《矿床地质》2007,26(3):237-248

文章以金云母、角闪石和白云母为测试对象,利用40Ar/39Ar同位素定年的方法,精确厘定了芙蓉超大型锡矿床的形成时间。研究结果表明,白腊水矿区3个金云母样品的40Ar/39Ar坪年龄分别为(150.6±1.0)Ma、(157.3±1.0)Ma和(154.7±1.1)Ma;热液成因角闪石的坪年龄为(156.9±1.1)Ma。淘锡窝矿区云英岩中2个白云母样品的40Ar/39Ar坪年龄为(159.9±0.5)Ma和(154.8±0.6)Ma;因此芙蓉矿床的形成时间为151～160Ma,这与骑田岭主体花岗岩的侵入时间(151～162Ma)相吻合。湘南地区的柿竹园超大型W-Sn-Mo-Bi-F矿床、新田岭大型W矿床、瑶岗仙W矿床和黄沙坪Pb-Zn多金属矿床的形成时间亦集中在150～160Ma之间,因此,湘南有色金属矿化集中区可能主要集中在150～160Ma发生成矿,这种大规模成矿作用可能与中生代华南岩石圈的拉张、伸展作用密切相关。  相似文献   

Geology and C-O isotope geochemistry of carbonate-hosted Pb-Zn deposits, NW Guizhou Province, SW China     

DOU Song  ZHOU Jiaxi 《中国地球化学学报》2013,32(1):7-18

The Pb-Zn metallogenic district in NW Guizhou Province is an important part of the Yun-nan-Sichuan-Guizhou Pb-Zn metallogenic province, and also is one of the most important Pb-Zn producers in China. The hosting rocks of the Pb-Zn deposits are Devonian to Permian carbonate rocks, and the basement rocks are meta-sedimentary and igneous rocks of the Proterozoic Kunyang and Huili groups. The ore minerals are composed of sphalerite, galena and pyrite, and the gangue minerals are include calcite and dolomite. Geology and C-O isotope of these deposits were studied in this paper. The results show that δ13C and δ18O values of hydrothermal calcite, altered wall rocks-dolostone, sedimentary calcite and hosting carbonate rocks range from -5.3‰ to -0.6 ‰ (mean -3.4‰) and +11.3‰ to +20.9 ‰ (mean +17.2‰), -3.0‰ to +0.9 ‰ (mean -1.3‰) and +17.0‰ to +20.8‰ (mean +19.7‰), +0.6‰ to +2.5 ‰ (mean +1.4‰) and +23.4‰ to +26.5 ‰ (mean +24.6‰), and -1.8‰ to +3.9‰ (mean +0.7‰) and +21.0‰ to +26.8‰ (mean +22.9‰), respectively, implying that CO2 in the ore-forming fluids was mainly a result of dissolution of Devonian and Carboniferous carbonate rocks. However, it is difficult to evaluate the contribution of sediment de-hydroxylation. Based on the integrated analysis of geology, C and O isotopes, it is believed that the ore-forming fluids of these carbonate-hosted Pb-Zn deposits in this area were derived from multiple sources, including hosting carbonate rocks, Devonian to Permian sedimentary rocks and basement rocks (the Kun-yang and Huili groups). Therefore, the fluids mixing is the main precipitation mechanism of the Pb-Zn deposit in this province.  相似文献