湘东北涧溪冲新太古代变质沉积-火山岩岩石矿物学和岩石地球化学研究

通过区域地质调查研究,在湘东北文家市涧溪冲村原中元古代冷家溪群新发现一套基本无序的变质沉积-火山岩系。根据岩石矿物学、岩石地球化学研究表明,涧溪冲变质沉积-火山岩系为变质火山岩夹变质粘土质沉积岩,属绿片岩—高绿片岩相。变质火山岩的原岩为大洋拉张环境下形成的以低钾拉斑玄武岩为主,低钾玄武安山岩次之的火山-次火山岩系,其物源为亏损地幔。变火山岩Sm-Nd全岩等时线年龄为(2594±48)Ma,其形成时代可能是新太古代。因此,与传统的中元古代冷家溪群的岩石组合、形成环境、形成时代、变质变形都具有明显不同的特征,原冷家溪群应予以解体。     

湘东北涧溪冲变质火山岩的Sm-Nd同位素年龄及其成因

最近的区域地质调查研究发现,湘东北地区原中元古代冷家溪群实际上应划分为4部分,它们均形成于不同的时代和不同的构造环境,将其中分离出的最老的基本无序的变质沉积—火山岩系建立为"涧溪冲岩群"。根据其岩石学、岩石地球化学及同位素年代学等方面的研究认为:"涧溪冲岩群"是变质火山岩夹变质粘土质沉积岩经构造叠置起来的变质岩系,属绿片岩相—高绿片岩相。变质火山岩的Sm Nd全岩等时线年龄为(2594±48)Ma,其形成的地质时代可能是新太古代。变质火山岩的原岩为在大洋拉张环境下形成的以拉斑玄武岩为主、钙碱性玄武岩次之的火山—次火山岩系,其物源为亏损地幔。     

东秦岭“武关岩群”斜长角闪岩Sm-Nd同位素年龄及其地质意义

东秦岭商丹断裂带南侧的“武关岩群”是从原泥盆系刘岭群北侧解体出来的变质沉积—火山岩系。已获得该构造岩石地层单位中斜长角闪岩（变质基性火山岩）ＳｍＮｄ同位素等时线年龄为（１３８２±３０）Ｍａ，钕同位素初始比值ＩＮｄ＝０．５１１１８６±１（２σ），εＮｄ（Ｔ）＝＋６．５１。表明武关岩群”变质岩系主体形成时代为中元古代，这一结果必将导致人们重新认识秦岭造山带的构造发展演化过程     

秦岭岩群和碧口岩群层序时代析重新厘定

秦岭岩群和碧口岩群因构造复杂、化石贫乏，多年来对其层序和时代的意见极不统一。笔者通过地层清理，并结合前人所获得的成果，对这两个岩群的层序和时代进行重新厘定。秦岭岩群包括云母石英片岩、大理岩、片麻岩三套岩石组合，据同位素年龄和区域地层对比定为早元古代；从原秦岭岩群中分解出峡河岩群，据同位素年龄定为中晚元古代。碧口岩群包括变火山岩和变沉积碎屑岩两套岩石组合，据同位素年龄和微古植物化石定为中晚元古代；从     

南秦岭凤凰山地区元古代构造基底特征

依据在原划武当岩群中获得的 1 6 86± 4 5Ma (锆石U -Pb)同位素测年资料 ,结合岩石学、岩石地球化学及区域地层对比 ,从中解体出姚坪岩组。通过岩石学、岩石地球化学、构造特征、变质变形特征研究及形成环境探讨认为 :南秦岭凤凰山元古代武当岩群 (包括姚坪岩组、杨坪岩组 )变质火山岩系为古—中元古代时期多岛洋构造环境过渡基底建造 ;耀岭河岩组浅变质火山岩为本区Rodina事件的产物。该成果对南秦岭构造基底的组成、发展、演化研究具有重要意义。     

滇西漕涧地区崇山变质杂岩中崇山岩群的时代与构造属性

滇西崇山变质杂岩带位于三江造山带"峰腰"的北段,带内构造挤压变质作用强烈,主体由一套中-深变质岩系（崇山岩群）和晚期花岗岩组成.其中崇山岩群历来被认为是元古代的结晶基底,但至今无精确的年龄依据,其形成时代和构造属性存在较大争议,严重制约了对区域构造演化的认识.对滇西漕涧地区崇山岩群中的岩石组分开展了碎屑锆石U-Pb年代学及岩石地球化学研究,结果显示副变质岩中的锆石均具明显的磨圆特征和较大的岩浆核,其中3件样品的最小一组碎屑锆石年龄分别为366~412 Ma（平均值为395 Ma）、435~508 Ma（平均值为473 Ma）和673~704 Ma（平均值为689 Ma）,指示了其原始沉积时代应不早于395 Ma;岩石地球化学表明,副变质岩是一套活动大陆边缘或被动大陆边缘构造背景有关的大陆岛弧碎屑岩,变质基性岩和变质中性岩为同源异相,均具活动大陆边缘的弧火山岩特征.结合副变质岩和两类正变质岩的构造属性相同以及普遍具相互伴生关系的特点,该3类岩石应属同一套地层系统的不同物质组分,崇山岩群主体为一套成岩于晚古生代（236~395 Ma）和形成于陆缘弧环境的火山-沉积地层单元;并与南东侧澜沧增生杂岩的志留纪弧火山岩组合成原-古特提斯洋盆东侧不同时代多岛弧的构造格局.综合研究认为,崇山变质杂岩带内的中-深变质岩系（崇山岩群）不（全）是前人认为的元古代结晶基底建造,应为原-古特提斯洋盆向东俯冲在兰坪-思茅地块西缘形成的一套火山-沉积地层系统;崇山岩群主要由年轻的（晚古生代）地层岩石组成,由于后期遭受中生代和新生代变质变形作用后形成了现今所见的"古老"岩石面貌的中-深变质系.      

秦岭岩群中斜长角闪岩的年代学、地球化学特征及其地质意义

本文对秦岭岩群中的三个斜长角闪岩（变质沉积岩）样品进行了岩石学、锆石U-Pb年代学和岩石地球化学研究，限定了秦岭岩群的形成时代，讨论了秦岭岩群的构造背景及归属问题。锆石定年结果显示了971 Ma、1222 Ma和840 Ma三个最大沉积年龄。秦岭岩群是一个杂岩体，秦岭岩群中至少存在中元古代（较老组成部分）和新元古代早期（较新组成部分）的岩性单元。秦岭岩群变质沉积岩的锆石年龄峰主要集中在中元古代-新元古代早期，具有与扬子块体和华北块体明显不同的锆石年代学特征，秦岭岩群在中元古代-新元古代早期为独立发展的微陆块。结合秦岭岩群的年代学特征及前人的研究结果，秦岭岩群中的变质沉积岩应沉积于弧相关的构造环境。     

秦岭岩群和碧口岩群层序时代的重新厘定

秦岭岩群和碧口岩群因构造复杂、化石贫乏，多年来对其层序和时代的意见极不统一。笔者通过地层清理，并结合前人所获得的成果，对这两个岩群的层序和时代进行重新厘定。秦岭岩群包括云母石英片岩、大理岩、片麻岩三套岩石组合，据同位素年龄和区域地层对比定为早元古代；从原秦岭岩群中分解出峡河岩群，据同位素年龄定为中晚元古代。碧口岩群包括变火山岩和变沉积碎屑岩两套岩石组合，据同位素年龄和微古植物化石定为中晚元古代；从原碧口岩群中分解出鱼洞子杂岩，据同位素年龄和硅铁建造定为早元古一太古代。     

吉林省前寒武纪地层

吉林省前寒武纪地层可见有太古宙变质表壳岩系、古元古代中深变质火山-沉积岩系、吉南新元古代陆源碎屑岩-碳酸盐岩组成的盖层沉积岩系和吉北造山带新元古代变质火山-沉积岩系4种类型.其中太古宙地层龙岗陆块具有多陆块拼贴的特点,可划分为龙岗岩群(四道砬子河岩组、杨家店岩组)、夹皮沟岩群(三道沟岩组、老牛沟岩组)、板石沟岩群、南岗岩群(鸡南岩组、官地岩组)、清原岩群.分别代表白山镇地块、夹皮沟镇地块、板石沟地块、和龙地块和清原地块的变质表壳岩系,其中除龙岗岩群可能为中太古代外,其余地质体的时代均为新太古代.古元古代地层有集安岩群、光华岩群和老岭岩群,前两者为古元古代早期裂谷环境沉积,分别可进一步划分为蚂蚁河岩组、荒岔沟岩组、大东岔岩组、双庙岩组和同心岩组,沉积时限为2 300～2 100Ma;后者为古元古代晚期内克拉通凹陷沉积,可进一步划分为林家沟岩组/达台山岩组、珍珠门岩组、花山岩组、临江岩组和大栗子岩组,沉积时限为1 900～1 800Ma.吉南新元古代地层的岩石地层学属性基本清楚,按新元古代三分的观点,其中细河群及其以下地层时代为青白口纪.浑江群时代为震旦纪,吉南地区缺失南华系.吉林省北部造山带中沿色洛河-海沟-青龙村-江域一线的元古宙地层事实上为不同时代、不同性质的构造岩片堆叠体,属于构造地层学范畴;具有层状地层特征的仅有敦化地区的塔东岩群、蛟河地区的新兴岩组、九台地区的机房沟岩群、辽源地区的西保安岩组以及安图地区的万宝岩组,时代可暂置于新元古代.     

高级变质区岩石地层系统建立的思考与实践——以内蒙古大青山—乌拉山地区为例

作者通过两个项目的区域地质调查研究，在大青山—乌拉山及其邻区重建了早前寒武纪地层系统，将新建的美岱召岩群列入古元古代。对区内高级变质岩石地层进行重组，在麻粒岩系中划分了2个岩组，归并为桑干岩群，将乌拉山岩群划分为上、下两个亚岩群，下亚岩群片麻岩系，上亚岩群相当于集宁群，可称孔兹岩系。提出本区高级变质区的主期构造是穹形构造与穹间褶皱群构造组合样式(简称“穹—褶”构造)，确立了大型顺层滑脱构造系统是决定高级变质岩石地层空间分布、组成特征和相互关系的关键因素，提出了研究高级变质岩石地层系统建立的方法与步骤。     

吉林省南部早太古宙上壳岩地球化学特征

吉林省南部早太古宙上壳岩是太古宙高级区的组成部分,它包括变质火山岩和变质沉积岩,其中各类变质火山岩的地球化学特征与康迪统计的太古宙同类岩石大致可此。本区上壳岩随SiO_2含量增高,ΣREE逐渐增高。各类岩石普遍具Ce、Eu的负异常,表明它们具相同的成岩环境。     

碱性岩研究进展述评

碱性岩的概念曾有三种观点,现多数学者倾向于用化学方法来综合判别碱性岩:碱性岩就是根据化学成分判别其碱性程度属于碱性的岩浆岩。碱性岩物质来源较深,主要源自上地幔,形成于岩石圈拉张环境,是深部地球动力学过程在浅部地壳的直接表现和历史记录,因此对其研究是探索地球深部物质组成、物理化学环境、地壳上层构造和深部动力学过程的一个重要途径,碱性岩是除幔源岩石包体外另一类可提供地幔信息的岩石,是窥探地幔的窗口。20世纪后期以来,对这一类型岩石的研究越来越受到地球科学家们的重视,形成了新的研究热点。     

Correlation of hydraulic conductivity with stratigraphy in a fractured-dolomite aquifer, northeastern Wisconsin, USA

This study integrated surface and subsurface stratigraphic data with geophysical logs and hydrogeologic data in order to characterize the hydraulic properties of the Silurian dolomite in northeastern Wisconsin. Silurian stratigraphy consists of predictable alternations of characteristic facies associations. A vertical profile of hydraulic conductivity, obtained from short-interval packer tests in a core hole that penetrates a majority of the Silurian section, indicates that hydraulic conductivity ranges over five orders of magnitude (10^–1 to 10^–6 cm/s). Matrix conductivity is generally low and varies with texture; the finer-grained restricted-marine and transitional facies being less permeable than the coarser-grained open-marine facies. High-conductivity values are generally associated with bedding-plane fractures, and fracture frequency is greater in the restricted-marine facies. High-flow features in 16 wells were identified using fluid-temperature/resistivity and heat-pulse flowmeter logs. Natural-gamma logs were used to identify the stratigraphic position of flow features in each well and to correlate flow features to specific stratigraphic horizons. By combining stratigraphic, geophysical, and hydrogeologic data, 14 high-permeability zones within the Silurian aquifer have been identified and correlated in wells more than 16 km apart. These zones parallel bedding, appear most pronounced at contacts between contrasting lithologies, and are most abundant in restricted-marine lithologies. Electronic Publication     

Delineation of capture zones for municipal wells in fractured dolomite, Sturgeon Bay, Wisconsin, USA

A wellhead protection study for the city of Sturgeon Bay, Wisconsin, USA, demonstrates the necessity of combining detailed hydrostratigraphic analysis with groundwater modeling to delineate zones of contribution for municipal wells in a fractured dolomite aquifer. A numerical model (MODFLOW) was combined with a particle tracking code (MODPATH) to simulate the regional groundwater system and to delineate capture zones for municipal wells. The hydrostratigraphic model included vertical and horizontal fractures and high-permeability zones. Correlating stratigraphic interpretations with field data such as geophysical logs, packer tests, and fracture mapping resulted in the construction of a numerical model with five high-permeability zones related to bedding planes or facies changes. These zones serve as major conduits for horizontal groundwater flow. Dipping fracture zones were simulated as thin high-permeability layers. The locations of exposed bedrock and surficial karst features were used to identify areas of enhanced recharge. Model results show the vulnerability of the municipal wells to pollution. Capture zones for the wells extend several kilometers north and south from the city. Travel times from recharge areas to all wells were generally less than one year. The high seasonal variability of recharge in the study area made the use of a transient model necessary. Electronic Publication     

西藏南羌塘盆地达卓玛地区油气地质条件研究

前人在南羌塘达卓玛地区零星发现了一些地表油气显示并采集了少量的烃源岩进行分析,但勘查程度总体较低,未开展系统的生、储、盖研究。结合前人资料,通过野外石油地质调查、样品采集、室内分析、对比研究等手段,对南羌塘盆地达卓玛地区的烃源岩、储集岩、盖层等油气地质条件进行了分析,认为研究区阿堵拉组泥岩、页岩为好烃源岩,色哇组泥岩、粉砂质泥岩为差—中等烃源岩,布曲组、夏里组和索瓦组发育差烃源岩; 储集岩主要为阿堵拉组砂岩和布曲组白云岩; 盖层有泥质岩、灰岩和石膏,以Ⅰ、Ⅱ类盖层为主。野外调查中发现了大量地表油气显示,盆地经历了油气生成、运移、聚集和散失的过程,具有油气生成的物质基础和成藏的油气地质条件。建议在油气存储条件良好的达卓玛背斜布置钻井,进一步开展深部研究,力争实现该地区油气突破。     

Study on petroleum geological conditions in Dazhuom area of Southern Qiangtang Basin of Tibet

Previous researchers in Dazhuoma area of Southern Qiangtang Basin have found some sporadic oil and gas on the surface and collected a small amount of source rocks for analysis, but the exploration degree was generally low and they have not carried out systematic analysis of the generation, storage and cap of oil and gas. Based on the previous data, the authors in this paper have studied the characteristics of the source rocks, reservoir rocks and cap rocks in Dazhuoma area of Southern Qiangtang Basin by means of field petroleum geological survey, sample collection, indoor analysis and comparative research. The results suggest that the mudstone and shale of Adula Formation in the study area are considered as good source rocks, and the mudstone and silty mudstone of Sewa Formation are poor-medium source rocks, while Buqu Formation, Shari Formation and Suowa Formation are poor source rocks. The main reservoir rocks are the sandstone of Adula Formation and the dolomite of Buqu Formation. The cap rocks are argillaceous rocks, limestone and gypsum, and are mainly Ⅰ and Ⅱ cap rocks. Furthermore, the discovery of oil exposure shows that this basin has underwent the process of oil and gas generation, migration, gathering and losing, which builds the material foundation of oil and gas generation and the petroleum geological conditions of hydrocarbon accumulation. It is suggested that more drilling should be arranged in Darzhuoma anticline with good oil and gas storage conditions, and further deep research should be carried out to achieve oil and gas breakthrough in this area.     

On the radiogenic heat production of metamorphic,igneous, and sedimentary rocks

Sedimentary rocks cover-73% of the Earth's surface and metamorphic rocks account for approximately91% of the crust by volume. Understanding the average behavior and variability of heat production for these rock types are vitally important for developing accurate models of lithospheric temperature. We analyze the heat production of ～204,000 whole rock geochemical data to quantify how heat production of these rocks varies with respect to chemistry and their evolution during metamorphism. The heat production of metaigneous and metasedimentary rocks are similar to their respective protoliths. Igneous and metaigneous samples increase in heat production with increasing SiO_2 and K_2 O, but decrease with increasing FeO, MgO and CaO. Sedimentary and metasedimentary rocks increase in heat production with increasing Al_2 O_3, FeO, TiO_2, and K_2 O but decrease with increasing CaO. For both igneous and sedimentary rocks, the heat production variations are largely correlated with processes that affect K_2 O concentration and covary with other major oxides as a consequence. Among sedimentary rocks,aluminous shales are the highest heat producing(2.9 μW~(-3)) whereas more common iron shales are lower heat producing(1.7 μW m~(-3)). Pure quartzites and carbonates are the lowest heat producing sedimentary rocks. Globally, there is little definitive evidence for a decrease in heat production with increasing metamorphic grade. However, there remains the need for high resolution studies of heat production variations within individual protoliths that vary in metamorphic grade. These results improve estimates of heat production and natural variability of rocks that will allow for more accurate temperature models of the lithosphere.     

包含变质岩分类三要素的主要变质岩分类表

变质岩分类的三要素是:变质岩的物质成分(化学成分、矿物成分)、变质岩的组构(结构、构造)和变质岩的成因(变质作用类型和形成变质岩的物理化学条件).由于变质岩的化学成分、矿物成分、组构特征和形成变质岩的地质环境十分复杂,致使至今尚无以变质岩分类三要素为基础的、内容比较完善的分类方案.本文中主要变质岩的分类是以其分类三要素为基础编制的,首次将不同成因的变质岩类并列于同一表中、将鉴定变质岩的主要标志性矿物成分和组构特征列入同一分类表中.该分类对鉴定变质岩石具有可操作性和实用性,分类表中涵盖了自然界主要的变质岩石.     

塔里木盆地西南地区碎屑岩储集层特征与评价

目前巴楚隆起的下古生界、麦盖提斜坡区的石炭-二叠系、西南缘山前的中新生界3个主要勘探目的层,均发育有碎屑岩类储层.该区碎屑储集岩成岩环境可划分为酸性成岩环境和碱性成岩环境两种类型,储层重点层位为石炭系和古近系.将碎屑岩储层成岩作用归纳为建设性和破坏性成岩作用,建设性成岩作用主要为砂岩中可溶组份发生的各种溶蚀及成岩晚期构造应力作用,研究区碎屑岩次生孔隙发育带多发育在2 800~6 000 m深度,与该区古地温梯度较低有直接联系.     

CO2矿物捕获能力的研究进展

全球碳存储的研究表明, CO2最稳定的存储方式是 CO2的矿物捕获, 即将 CO2注入到地下,使其以方解石、菱铁矿、白云石及片钠铝石等碳酸盐矿物的形式存在.适合 CO2矿物捕获的岩石类型主要有火山岩、砂岩和火山碎屑岩.分析了3种岩石类型的金属元素含量、金属元素的释放能力、与 CO2反应生成的矿物类型及对 CO2的捕获量,并比较了3种岩石类型对 CO2矿物捕获能力的差异.其中玄武岩等火山岩的金属离子含量高,但其孔隙空间有限,制约了成岩反应,且 CO2注入后具有逸散的风险;砂岩分布广泛,有足够的孔隙利于流体注入,但是金属离子含量相对较低,对 CO2的矿物捕获所需时间相对较长;火山碎屑岩则结合了前2种岩石类型在矿物捕获方面的优势,是一种理想的 CO2矿物捕获的岩石类型.