Petrogenesis of Two Types of Archean TTGs in the North China Craton: A Case Study of Intercalated TTGs in Lushan and Non-intercalated TTGs in Hengshan

TTG(Tonalite-Trondhjemite-Granodiorite) gneisses,a major component of Precambrian continental crust,play a significant role in understanding the process and mechanism of the crustal evolution in the early periods of the Earth. In terms of field occurrence,there are two kinds of Archean TTGs in the NCC(North China Craton): intercalated and non-intercalated TTGs. In this contribution,we make a comprehensive comparison of these two types of TTGs from the typical areas(Lushan and Hengshan) in the NCC with an aim to constrain their petrogenesis. The results suggest that they have similar mineral assemblages of Pl + Qtz + Bt ± Amp ± Kfs but different field appearances and geochemical compositions,thus probably reflecting different source materials and tectonic settings. Differences in the contents of characteristic elements,such as Sr,REE and HFSE,suggest that the nonintercalated TTGs in Hengshan were generated at deeper levels than those of intercalated TTGs in Lushan. Constraints from element contents and geochemical modeling results are consistent with derivation from dual sources involving both garnet amphibolite and rutile-bearing eclogite residues for the non-intercalated TTGs in Hengshan,whereas the compositions of intercalated TTGs in Lushan indicate that they were formed by partial melting with amphibolite to garnet-amphibolite residues. Moreover,accumulation of plagioclase is also required in the petrogenesis of intercalated TTGs in Lushan,at least for part of them. In addition,the non-intercalated TTGs in Hengshan display distinctly higher Mg O,Mg#,Cr and Ni values and lower SiO_2 average contents compared to the intercalated TTGs in Lushan. These features suggest that the former magma,at least a part,might have interacted with the mantle wedge during ascent. Considering all the above factors and in combination with the whole-rock Nd and zircon Hf isotopic data,it is suggested that the non-intercalated TTGs in Hengshan were produced by partial melting of subducted slab contaminated by the overlying mantle wedge at deeper levels and high pressures,whereas the intercalated TTGs in Lushan were generated by melting of the thickened lower crust at lower pressures and shallower depths. The tectonic settings of the two types of TTGs shed new light on the growth of the NCC.     

深部钻探铝合金钻杆开发应用

铝合金钻杆具有质量轻、比强度高、钻进深度大等特点,开发并应用铝合金钻杆对提高我国难进入地区钻探施工效率、推动深部科学钻探技术进步以及节能降耗等具有重大现实意义。本文介绍了我国铝合金钻杆批量化、系列化开发与应用的现状,并重点分析了铝合金钻杆应用技术特点、试制关键技术、室内试验和推广应用情况;根据铝合金钻杆的实钻应用情况及研发趋势,提出了我国铝合金钻杆开发的新构想。     

甘肃武威盆地页岩气“武页1井”成膜低固相冲洗液的应用

“武页1井”是甘肃省地质调查院实施的一口页岩气基础地质条件调查井,主要目的是为了查明页岩层段的分布。地层岩性主要为泥岩、砂岩、页岩、碳质板岩、灰岩。浅层倾角大、胶结性差、破碎、井壁强度低。现场采用成膜低固相冲洗液体系,解决了地层破碎、坍塌掉块和水敏性钻探施工难题,体系具有护壁性、抑制性和胶结性。使用中取得了较好的效果,保证了该项目的顺利施工。     

页岩气基础地质调查皖南地1井钻探施工技术

皖南地1井是部署在安徽省南陵县烟墩镇的一口页岩气基础地质调查井。文章详细介绍了该井的钻探施工工艺技术以及遇到复杂问题的处理方法,并对钻效进行了分析,提出了实现优质高效钻探的措施。项目的顺利实施,梳理了皖南地区地层层序,为页岩气储层理论推测提供了有力的实物数据支撑和验证。     

围压和孔隙结构对不同粒级砂岩孔隙度渗透率的影响实验研究

孔隙度和渗透率是储层评价的两个重要参数.岩石毛管压力曲线和核磁共振T2谱图是描述储层微观结构特征的重要参数.通过测量不同压力条件下岩心样品的孔隙度和渗透率,得到了孔隙度和渗透率随压力的变化情况.实验结果表明：孔隙度和渗透率随着压力的增加而降低,并且与压力服从对数函数变化规律.不同孔隙度渗透率区间的砂岩样品,孔隙度和渗透率随着压力变化的趋势不同.通过测量不同粒级砂岩样品的毛管压力曲线和核磁共振T2谱图,证实了孔隙结构对孔隙度和渗透率的影响,微观孔隙结构是决定渗透性好坏的关键因素.     

湖南湘东钨矿含矿石英脉辉钼矿Re-Os定年及地质意义

湘东钨矿是一个典型的石英脉型钨锡多金属矿床,发育百余条含矿石英脉,矿脉陡立,从北到南走向呈NE、NEE和EW向,反映了矿脉形成时处于近NW-SE向区域拉伸状态。矿区内的老山坳断层分割了重要的南、北两组矿脉。北组脉具有毒砂-黄铜矿-黑钨矿等矿物组合,富含金属硫化物,多具有平行脉壁的条带状构造;南组脉则主要体现辉钼矿-黑钨矿-黄铜矿-闪锌矿-方铅矿等矿物组合,金属硫化物含量较少,具有块状构造。本次研究通过对南组脉辉钼矿Re-Os同位素测年,获得等时线年龄为150.4±1.5 Ma(MSWD=0.52),模式年龄加权平均值为150.7±2.3 Ma(MSWD=0.10),代表成矿时间。含矿石英脉的形成略晚于区内燕山期二云母花岗岩(154.4±2.2 Ma)和煌斑岩(152.1±0.9 Ma)的侵位,指示含矿石英脉在成因上与燕山早期岩浆活动密切相关。事实上,包括湘东钨矿在内的南岭钨锡多金属成矿省均形成于165~150 Ma期间,具有统一的地球动力学背景,即由太平洋板块俯冲和俯冲板片断离所引起的弧后伸展环境。     

准噶尔盆地南缘西段中、上侏罗统沉积演化及控制因素分析

针对准噶尔盆地南缘中、上侏罗统沉积体系演化控制因素不清、沉积模式不明等问题,通过对多条露头剖面精细解剖、详尽写实沉积特征描述等手段,分析了其垂向序列、砂体叠置方式、水动力条件、沉积体系演化及控制因素。研究表明准南中、上侏罗统自下而上分别发育辫状河沉积、曲流河沉积和扇三角洲沉积,古气候与构造造成的水动力条件的变化是控制这种沉积演化的主要因素。其中头屯河组底部发育辫状河沉积,古气候温暖湿润,形成堆叠型砂体叠置方式;中部发育辫-曲转换沉积,古气候开始初步干旱,形成紧密叠置型砂体;上部发育曲流河沉积,降雨量较少古气候干旱,形成孤立河道型砂体。齐古组发育季节性曲流河沉积,古气候较为干旱,在湿润期降雨量较充足时发育侧向迁移型砂体,干旱期则发育侧向连片型砂体。喀拉扎组发育扇三角洲沉积,古气候整体炎热干旱,构造活动剧烈,碎屑水道在扇三角洲平原构成垂向切割型砂体,而前缘水下分流河道则构成侧向切割型砂体。     

新特提斯洋晚白垩世演化特点:来自泽当共国日二长花岗岩年代学、地球化学及Sr-Nd同位素证据

为加深对西藏泽当地区新特提斯洋演化的认识,对西藏泽当蛇绿混杂岩带内的共国日二长花岗岩进行了岩石学、岩石地球化学、同位素及年代学等研究,研究显示:共国日二长花岗岩岩体规模小、岩性稳定,LA-ICP-MS锆石U-Pb年龄为(90.40±0.68)Ma,属晚白垩世;岩石地球化学具高硅、富铝、富钾、低钛和准铝质钙碱性花岗岩特征;轻稀土富集、重稀土亏损,具明显的负Eu异常,微量元素表现为相对富集Rb、K、Ba、Th、U等大离子亲石元素,显著亏损Nb、P、Ti等高场强元素;(⁸⁷Sr/⁸⁶Sr)_i=0.705 708~0.706 284,(¹⁴³Nd/¹⁴⁴Nd)_i=0.512 689~0.512 716,ε_Nd(t)=2.00~2.51。以上特征表明,位于泽当蛇绿混杂岩带内的共国日二长花岗岩属于I型花岗岩,由正常岛弧岩浆形成,应为晚白垩世新特提斯洋向北俯冲形成的岛弧环境下俯冲带上部地壳部分熔融的产物,其不属于泽当蛇绿岩的组成部分,表明在90 Ma前泽当洋内弧已经消失。