浙西北钟吕群流纹岩锆石U-Pb年龄及其年代地层学意义

 钟吕群出露于浙西北地区,为一套强变形、浅变质的碎屑岩-火山岩系,其下未见底,上被南华纪休宁组不整合覆盖。传统上将其对比于赣东北双桥山群。本文主要研究钟吕群流纹岩的锆石U-Pb 年龄。样品A120408-4 采自苏庄断层以北,层位上属钟吕群的中上部,岩性为灰白色致密块状流纹岩,强烈片理化。样品A120408-4 中获得大量锆石,完成LA-ICP-MS 锆石UPb定年测点38 个,获得年龄加权平均值为(777.1±3.6)Ma,结合地层特点及变质变形特征,得出钟吕群主体相当于河上镇群上墅组,应属扬子古陆新元古代晚期大陆裂谷的地质记录。     

河北省沽源县大官厂铀钼矿床围岩蚀变与成矿

从区域成矿条件、矿床地质特征、围岩蚀变及蚀变岩石的元素含量研究入手,对大官厂矿床围岩蚀变与矿化的关系进行了论述。研究表明,矿区围岩蚀变始终伴随成矿作用的每个阶段。蚀变类型具有多样性,但蚀变分带不明显,矿前期为面型蚀变,呈碱交代(以钾长石化为主)特征;成矿期呈线型蚀变(强赤铁矿化-弱赤铁矿化-水云母化)叠加于面型蚀变之上;矿后期多为脉状分布于早期已蚀变的岩石裂隙中,呈酸性蚀变组合(以水云母化为主)。通过对该矿床围岩蚀变类型、叠加关系的研究,据此对矿床的成因类型进行探讨。     

滇西碧罗雪山地区忙怀组火山岩地球化学特征

滇西碧罗雪山一带,澜沧江岛弧带上发育了中三叠纪忙怀组火山岩,岩石类型主要是流纹岩.常量元素SiO2、K2O、Na2O、Al2O3明显偏高,MgO较低,TiO2中等的特征.里特曼指数σ1.39~3.01,为钙碱性系列,在log t-logσ图解中全部落入造山带区.碧罗雪山一带流纹岩的大离子亲石元素含量变化比较小,微量元素表现为大离子亲石元素Rb、Sr、Ba明显富集,高场强元素Th也相对富集.Eu负异常明显,轻稀土元素富集,稀土分配模式为轻稀土富集右斜型.微量元素在Rb-(Yb+Nb)图解及Rb-(Yb+Ta)图解中大多数落入碰撞带花岗岩区和火山弧花岗岩区.综合岩石地球化学特征及构造环境判别图解指示,碧罗雪山地区忙怀组火山岩为澜沧江洋由西向东俯冲消减,由被动大陆边缘转化为活动大陆边缘过程中形成的岛弧火山岩.     

流纹岩类火山岩储层物性特征研究

火山岩油气藏储层岩石类型特殊、孔隙结构复杂,在开发过程中其储层物性将会对采出程度产生一定的影响,利用火山岩气田升深2-1井的流纹岩岩心、测井资料,通过对流纹岩岩石物性参数随净上覆岩层压力变化的实验研究,对实验结果进行处理分析,得出了一些有益的结论:该流纹岩岩石孔隙度随净上覆岩层压力呈多项式(三项式)函数变化关系、渗透率与净上覆岩层压力之间的关系满足幂指数关系、储层岩石的压缩系数与净上覆岩层压力之间的关系满足指数关系、岩石密度和孔隙度之间具有很好的线性关系。从而更进一步认识了该流纹岩储层的物性特征,为该特殊岩石气藏的合理开发提供了有利的基础资料。     

大兴安岭红山子盆地铀矿勘查新进展及其找矿意义

通过2010-2012年开展的新一轮铀矿补充勘查和基础地质研究,确认了沽源-红山子铀成矿带红山子盆地的含矿火山岩以高钾钙碱性流纹岩-碱性流纹岩组合为特征,属晚侏罗世早期新民组,发现铀钼矿体主要受NE向推覆构造控制,成矿期热液蚀变属碱交代型.红山子盆地赋矿火山岩的岩石组合和地质时代,与早白垩世早期高钾钙碱性流纹岩-碱性粗面岩组合为特征的沽源盆地张麻井铀钼矿床的赋矿围岩明显不同,是沽源-红山子铀成矿带一个新的找矿层位;红山子铀钼矿床的控矿构造和热液蚀变特征,也不同于具有“上酸下碱”蚀变规律、矿体赋存在流纹斑岩与流纹岩接触带附近的张麻井铀钼矿床,一方面证实断裂构造在铀矿体定位中具有控制作用,另一方面暗示红山子盆地抬升剥蚀程度较大、保矿条件不好,指示沽源-红山子铀成矿带铀矿靶区的圈定应注意保矿条件的分析.     

哈勒盖图地区白音高老组流纹岩岩石地球化学特征及其地质意义

在样品采集和分析基础上,探讨内蒙古西乌旗哈勒盖图地区早白垩世白音高老组流纹岩的岩石地球化学特征及其地质意义.主量元素分析结果显示其具有高硅、富碱、高铝、低MgO、CaO、TiO2、MnO的特征,稀土元素与微量元素地球化学特征显示其类似于A型花岗岩特征;低Ti/Y、Nb/Y与Ti/Zr比值、高Rb/Nb与Rb/Y比值以及Sr、Eu强烈亏损,表明其为上地壳物质部分熔融成因,形成于早白垩世非造山板内伸展环境.研究结论揭示了该时期大兴安岭地区构造-岩浆的重要作用,对该地区今后的找矿工作具有重要的指导意义.     

塔北哈拉哈塘流纹岩的离子探针锆石U-Pb 年代学: 对塔里木溢流玄武岩主期喷发时代的约束

塔里木北部哈拉哈塘地区存在流纹岩覆盖于玄武岩之上的迭置关系。对上层流纹岩采用SIMS锆石U-Pb 法精确测定其年龄为 287.3 ±2.0 Ma。该年龄限定该区玄武岩的喷发时代不晚于 287 Ma,证明塔里木溢流玄武岩的主喷发期应不晚于 287 Ma,而非前人提出的大约 275 Ma。     

Origin of middle Miocene leucogranites and rhyolites on the Tibetan Plateau: Constraints on the timing of crustal thickening and uplift of its northern boundary

Leucogranites play a significant role in understanding crustal thickening, melting within continental collisional belts, and plateau uplift. Field investigations show that Miocene igneous rocks from the Hoh Xil Lake area mainly consist of two-mica leucogranites and rhyolites. We studied the Bukadaban two-mica leucogranites and the Kekao Lake, Malanshan and Hudongliang rhyolites by zircon U-Pb, muscovite and sanidine 40Ar/39Ar geochronology, and whole-rock geochemical and Sr-Nd isotopic analysis. Results yielded crystallization and cooling ages for the Bukadaban leucogranites of 9.7±0.2 and 6.88±0.19 Ma, respectively. Extrusive ages of the Kekao Lake and Malanshan rhyolites are 14.5±0.8 and 9.37±0.30 Ma, respectively. All rocks are enriched in SiO2 (70.99%-73.59%), Al2O3 (14.39%-15.25%) and K2O (3.78%-5.50%) but depleted in Fe2O3 (0.58%-1.56%), MgO (0.11%- 0.44%) and CaO (0.59%-1.19%). The rocks are strongly peraluminous (A/CNK=1.11?1.21) S-type granites characterized by negative Eu anomalies (δ Eu=0.18-0.39). In also considering their Sr-Nd isotopic compositions (87Sr/86Sri=0.7124 to 0.7143; δ Nd (9 Ma) =-5.5 to -7.1), we propose that these igneous rocks were generated through dehydration melting of muscovite in the thickened middle or lower crust of northern Tibet. Melting was probably triggered by localized E-W stretching decompression in the horse tails of Kunlun sinistral strike-slip faults. Reactivation of the Kunlun strike-slip faults, accompanied by emplacement of leucogranite and eruption of rhyolite in the Hoh Xil Lake area, indicates that large-scale crustal shortening and thickening in northern Tibet mainly occurred before 15 Ma. In addition, these findings suggest that the northern Tibetan Plateau attained its present elevation (~5000 m) at least 15 Ma ago.     

流纹岩滤料的性能测试及过滤试验

对流纹岩滤料的初步试验研究表明，流纹岩滤料的性能明显优于石英砂，是比较理想的天然无机滤料，具有进一步研究开发价值．     

Petrogenesis of the Neoproterozoic bimodal volcanic rocks along the western margin of the Yangtze Block： New constraints from Hf isotopes and Fe/Mn ratios

High-precision major element and Hf isotope data are reported for the Neoproterozoic Suxiong volcanic rocks along the western margin of the Yangtze Block. These volcanic rocks have variable εHf（T） values and Fe/Mn ratios. The relatively primitive basalts have high Fe/Mn ratios and high Hf-Nd isotopic compositions, indicating that they were generated by partial melting of garnet clinopyroxene in mantle plume at high pressure. Thus, the Suxiong basalts are genetically related to the proposed Neoproterozoic superplume. On the contrary, a few differentiated basalts have low Fe/Mn ratios and low Hf-Nd isotopic compositions. They are likely to experience assimilation-fractional crystallization process. The Suxiong rhyolites have consistent Hf and Nd model ages of 1.3-1.4 Ga. They are likely generated by shallow dehydration melting of pre-existing young arc igneous rocks associated with the basaltic underplating/intrusion in a continental rift.