黑龙江省东部晚三叠世-中侏罗世硅质岩地球化学特征及形成环境

黑龙江省东部那丹哈达增生杂岩主要由晚三叠世-中侏罗世含放射虫硅质岩组成,并夹有镁铁-超镁铁质杂岩和晚古生代浅海沉积岩.对黑龙江省东部石场、勤得利和胜利农场地区硅质岩分析显示,样品Al₂O₃、TiO₂、CaO、Al₂O₃/（Al₂O₃+TFe₂O₃）及ΣREE整体上偏低,具有较高的SiO₂含量,为纯硅质岩.结合Al-Fe-Mn三角图和K₂O/Na₂O值,表明该地区硅质岩的形成过程与海底热液作用无关.元素判别图解及地球化学特征揭示,黑龙江东部三个地区的硅质岩形成于大陆坡及边缘海环境.     

安徽金寨三仙山地区梅山群碎屑岩成分及其对物源区构造属性和地层时代的意义

安徽金寨三仙山地区位于大别山北缘,该地梅山群主要为一套轻微变质的碎屑岩系。砂岩碎屑组分统计表明,砂岩类型主要为岩屑石英砂岩、岩屑石英杂砂岩,石英、长石、岩屑的平均含量为87.21%、1.67%、9.64%,杂基含量为15%,石英几乎全为单晶石英（95.79%）,长石以斜长石为主,岩屑主要为沉积岩屑（75.49%）,其次为变质岩屑（24.51%）。碎屑岩地球化学元素平均含量为：SiO₂（75.99%）,Al₂O₃（11.96%）,MgO（0.72%）,CaO（0.10%）,Fe₂O₃（4.02%）,K₂O（1.70%）,Na₂O（0.26%）。ΣREE=170.49×10^-6（74.49×10^-6～309.42×10^-6）,LREE/HREE=11.16（7.89～14.26）,轻稀土略有富集,δEu=0.72（0.59～0.90）,La/Yb=22.08（13.01～31.18）,（La/Yb）_N=14.89（8.77～21.02）,δCe=0.84（0.42～0.97）。碎屑岩地球化学特征指示三仙山地区梅山群母岩主要为古老沉积岩、长英质火山岩和古老变质基底,具有多重物源区。梅山群构造背景较复杂,主要为被动大陆边缘和活动大陆边缘,其次为大陆岛弧。三仙山地区梅山群碎屑岩的源岩成分、构造背景与商城-固始地区石炭系有很大差别,故其地层时代有待于进一步研究。     

漠河盆地中侏罗世绣峰组物源分析及构造意义

漠河盆地位于大兴安岭北部,绣峰组作为漠河盆地最下部层位,其形成时代、物源区特征及大地构造背景等对研究漠河盆地的形成与演化具有重要意义。本文对漠河盆地西南缘绣峰组砂岩进行了碎屑锆石LA-ICP-MS U-Pb年代学和地球化学分析。锆石年代学研究表明,147组碎屑锆石年龄分布于778～181 Ma之间,显示出一个主峰约为198 Ma,分为778、528～393、252、223～181 Ma等4个年龄组,分别与新元古代Rodinia超大陆裂解事件、额尔古纳地块与兴安地块碰撞拼合岩浆活动事件、古亚洲洋俯冲闭合岩浆活动事件和蒙古—鄂霍茨克俯冲闭合岩浆活动事件相对应。砂岩岩石地球化学分析结果显示：w(SiO₂)为70.59%～73.29%,w(Al₂O₃)为13.91%～14.93%,Al₂O₃/SiO₂值为0.19～0.21,K₂O/Na₂O值为0.66～1.22,化学蚀变指数(CIA)值为52.58～56.04,平均为5...     

松辽盆地北部上二叠统林西组地球化学特征及地质意义

为探讨松辽盆地北部林西组地球化学特征、沉积环境及构造背景,对该区黑富地1井所钻遇的上二叠统林西组暗色泥质板岩进行主量元素、微量元素和稀土元素测试分析,结果表明：样品主量元素平均质量分数SiO₂为65.05%、Al₂O₃为17.23%、CaO为2.58%、Na₂O为2.84%、K₂O为3.29%,K₂O/Na₂O值为0.20~3.48,A1₂O₃/（CaO+Na₂O）值为0.41~8.01;稀土元素w（∑REE）值介于80.68×10^-6~215.59×10^-6之间,平均值为173.41×10^-6,δEu值介于0.61~0.88之间,平均值为0.70,表现为Eu的负异常,δCe值介于0.91×10^-6~1.01×10^-6之间,为微弱的Ce负异常,LREE富集,HREE亏损;微量元素以亏损Nb、Ta、Sr,相对富集Rb、Ba、La、Ce、Pb、Nd、Sm为特征。样品元素分析和物源w（TiO₂）-w（Ni）、La/Th-w（Hf）等判别图解表明,林西组沉积物源具有多样性,主要来源于上地壳长英质物源,还有少量来自中、基性岩火成岩物源区。样品微量元素标准化蛛网图,稀土元素球粒陨石标准化配分模式图,K₂O/Na₂O-w（SiO₂）、Th-Co-Zr/10、F₂-F₁构造背景判别图及地球化学参数对比结果表明,松辽盆地北部林西组物源构造背景主要为活动大陆边缘和大陆岛弧,可能形成于靠近大陆岛弧的活动大陆边缘构造背景。林西组应形成于海陆过渡相到陆相环境,水体由半咸水逐渐转变为淡水。     

南海北部中央峡谷水道的岩相-地球化学特征及其源区性质

峡谷水道是南海北部琼东南盆地深水区主要储集层,乐东-陵水凹陷黄流组储集岩以粉、细砂岩为主,储层物性好.然而目前针对不同期水道主要物源供给及水道形成的母岩区性质、古风化程度等研究甚少.对中央峡谷西段水道的砂泥岩进行了岩石薄片与重矿物成分观察统计、岩石主量、微量/稀土元素分析,结果表明:岩石类型以岩屑石英砂岩和长石岩屑砂岩为主,崖城、陵水区重矿物分别为磁铁矿、白钛矿、锆石、电气石与白钛矿、石榴石、电气石、锆石的组合;地球化学特征表现为泥岩较砂岩SiO₂含量低,Fe₂O₃、MgO、K₂O、稀土含量偏高,与其含有高粘土矿物有关.砂、泥岩Al₂O₃/TiO₂、K₂O/Al₂O₃、K₂O/Na₂O比值说明物源区富石英、贫钾长石,分别为石英质沉积与中性火成岩源区;砂岩较泥岩具有较高SiO₂/Al₂O₃比值、低ICV、CIA、CIW值,表明源区经历了低-中等程度的风化作用,是稳定构造环境再循环沉积而成,泥岩的形成环境较砂岩动荡.      

东昆仑花石峡北部上二叠统格曲组源区特征:来自碎屑组成和岩石地球化学的证据

东昆仑南缘上二叠统（乐平统）格曲组为一套由砾岩、砂岩和钙质泥岩构成的扇三角洲-浅海碳酸盐台地相沉积组合,记录了东昆仑造山带海西-印支过渡期构造演化过程,是解析该构造演化过程的理想对象。通过分析花石峡北坦地克借地区格曲组碎屑岩的碎屑组成与主量、微量和稀土元素特征,探讨了其物源区属性。结果显示,砂岩类型为长石砂岩和岩屑长石砂岩,石英、长石和岩屑平均含量分别为50.9%、36.8%、12.4%,长石以钾长石为主,岩屑和砾石成分复杂。砂岩的SiO₂、Al₂O₃、TiO₂、TFe₂O₃、MgO、K₂O和Na₂O平均百分含量分别为62.06%、13.26%、0.44%、4.53%、3.02%、2.42%和3.18%;微量元素比值Th/Sc和Th/U较高,平均为1.06和7.71;稀土元素总量∑REE平均120.43×10-6,LREE/HREE和（La/Yb）_N均值分别为9.34和12,轻稀土相对富集,δEu平均为0.96,Eu异常不明显,REE特征与大陆岛弧背景区杂砂岩相似,与东昆仑地体加里东期俯冲-碰撞型火山弧花岗岩具有亲缘性。碎屑组分和主量、微量元素特征与判别图解揭示,格曲组砂岩物源区为海西旋回早期从东昆仑地体裂离的东昆南微地块,源岩以花岗岩为主,变质岩、沉积岩和酸性-基性火山岩较少,其中花岗岩形成构造背景为加里东期的大陆岛弧。结合区域地质和前人研究成果,认为格曲组为前陆盆地系统的隆后盆地沉积。     

内蒙古阿拉善右旗雅干地区二叠系埋汗哈达组硅质岩成因及其沉积环境

通过对内蒙古阿拉善右旗雅干地区好比如、杭乌拉剖面二叠系埋汗哈达组硅质岩岩石学特征、主量元素、稀土元素地球化学研究,探讨了硅质岩的成因及其沉积环境。地球化学测试结果显示：好比如剖面硅质岩SiO₂质量分数为89.83%~94.16%,平均值为92.01%,Al/（Al+Fe+Mn）值为0.49~0.65,平均值为0.56,δCe值为0.87~0.92,平均值为0.89;杭乌拉剖面硅质岩SiO₂质量分数为75.93%~90.14%,平均值为86.70%,Al/（Al+Fe+Mn）值为0.68~0.78,平均值为0.73,δCe值为0.89~0.94,平均值为0.90;在Al-Fe-Mn三角图上,样品全部落入生物成因硅质岩区,指示研究区硅质岩为海水生物沉积成因。好比如剖面硅质岩Al₂O₃/（Al₂O₃+Fe₂O₃）值为0.59~0.78,平均值为0.71,MnO/TiO₂值为0.17~0.88,平均值为0.41,（La/Ce）_N值为1.07~1.25,平均值为1.16,Ce_anom值为-0.059~-0.026,平均值为-0.043;杭乌拉剖面硅质岩Al₂O₃/（Al₂O₃+Fe₂O₃）值为0.78~0.86,平均值为0.83,MnO/TiO₂值为0.04~0.40,平均值为0.16,（La/Ce）_N值为1.02~1.15,平均值为1.10,Ce_anom值为-0.041~-0.001,平均值为-0.029;在硅质岩沉积环境判别图上,样品落在大陆边缘型硅质岩区域内,指示研究区硅质岩沉积于大陆边缘缺氧的水体环境。综合分析认为研究区早二叠世为大陆边缘滨海-浅海相沉积环境。     

北祁连山镜铁山地区镜铁山群岩石地球化学特征及其地质意义

镜铁山铁(铜)矿床是我国西北地区发现和勘探最早的大型铁(铜)矿床。对于铁矿床的成因,目前还存在不同的观点。笔者等对镜铁山铁铜矿床赋矿地层开展了岩石学和岩石化学成分分析,结果显示：变质石英砂岩的SiO₂平均含量为96.95%、Al₂O₃平均为1.36%、Fe₂O₃平均为0.31%,SiO₂/Al₂O₃平均值为73.26,K₂O/Na₂O平均值为12.54;除Sn以外,其他微量元素平均含量均低于后太古宙澳大利亚页岩(PAAS)值,稀土元素总量显著低于PAAS值,具有弱的Eu正异常,Ce异常不明显;铁碧玉岩SiO₂平均含量为85.67%、Fe₂O₃平均含量为10.19%、SiO₂/Al₂O₃平均为430.47、K₂O/Na<...     

鄂西南齐岳山须家河组物源及构造背景:来自岩石学、地球化学和锆石年代学的制约

为揭示鄂西南齐岳山地区晚三叠世须家河组物源与构造背景,以周家湾与颜家沟剖面为代表,对须家河组碎屑岩的颗粒组分、元素组成以及锆石年龄进行测试与统计.结果显示:砂岩碎屑颗粒石英含量高、岩屑与长石含量低,平均值分别为76.15%、8.90%与3.45%,具有锆石-板钛矿-磁铁矿-榍石-电气石重矿物组合,反映源岩以酸性岩或低级变质岩为主,Dickinson判别图解表明物源主要来自再旋回造山带;砂岩(TFe₂O₃+MgO)*与TiO₂*含量低,Al₂O₃/SiO₂比值低,K₂O/Na₂O比值高,最接近被动大陆边缘特征值;泥岩成分变异指数ICV分布于0.32~0.79之间,平均值为0.56,反映物源主要为再旋回沉积物;样品稀土元素配分模式、特征微量元素含量及比值指示晚三叠世沉积构造背景为被动与活动大陆边缘;碎屑锆石分为磨圆与自形两类,磨圆者具有2 480 Ma、1 880 Ma、832 Ma年龄峰值(n=133),年龄频数分特征与扬子陆块最接近;自形锆石具有435 Ma、217 Ma年龄峰值(n=42),年龄频数分布特征与秦岭造山带和雪峰造山带花岗岩年龄具有很好的对应关系.结合物源与构造背景判别图解,上述特征综合表明须家河组形成于被动大陆边缘(为主)与活动大陆边缘环境,其物源来自东南的雪峰造山带(为主)与北侧的秦岭造山带.      

黄骅坳陷中生界砂岩地球化学特征及意义

中生代黄骅坳陷位于华北克拉通汇聚与破坏的中心,为各物源的汇集地,记录了华北中生代盆地的构造及物源演化.对研究区中生界砂岩进行了主、微量元素测试分析,结果显示,样品SiO₂、Al₂O₃、Na₂O、K₂O和Fe₂O₃T平均含量分别为66.98%、13.65%、2.74%、3.03%和3.26%,砂岩为岩屑砂岩、长石砂岩和杂砂岩.砂岩CIA和ICV的平均值分别为56.12和0.94,均经历了一定的化学风化及再旋回作用.砂岩的母岩为长英质火成岩和再旋回沉积岩,并混杂少量基性火成岩.由三叠纪到白垩纪,中生界砂岩物源逐渐由华北北缘大陆弧演化为燕山造山带和黄骅坳陷内的岩浆作用及古隆起.      

The stratigraphy and composition of the Latterbarrow and Redmain sandstones,Lake District,England

The Latterbarrow Formation, 400 m thick, has been mapped and subdivided informally into three members. These consist of quartz wacke sandstone and, in the upper member only, intercalated mudstones. The formation unconformably overlies the fossiliferous Skiddaw Group of late Tremadoc to middle Arenig age and is overlain disconformably by volcanic rocks that have been attributed to the Borrowdale Volcanic Group. Chemically, the sandstones are characterized by very low concentrations of CaO, Na₂O, and K₂O and unusually high total iron. MnO and MgO, such that iron, as Fe₂O₃, exceeds Al₂O₃. Mudstone in the upper member is illite rich, has a high K₂O content and is compositionally similar to K-bentonites derived from volcanic ash. Sedimentary structures and petrography suggest that the sediments were deposited in a sandy estuary and were derived from a similar source area to that of the Skiddaw Group. Throughout the succession there is evidence of distal volcanism, probably representing the earliest eruptions of the Borrowdale volcanic episode. The Redmain Formation, 100 m thick, is unconformably overlain by Carboniferous rocks but its relationship to the underlying Skiddaw Group is unknown. Though this lithic arenite shows some petrographic and geochemical similarities with the Latterbarrow sandstone, differences are such that it is possible they are not equivalent in age. The Redmain sandstone may be derived from the erosion of Skiddaw Group rocks.     

内蒙古乌兰浩特沙巴尔吐地区上二叠统林西组重新划分

本文作者在内蒙古乌兰浩特北沙巴尔吐一带开展1∶5万区调时,根据岩石组合、古生物特征、沉积环境等对出露于该地区扎格斯台一带的一套黑色砂板岩进行了重新厘定。重新厘定后的林西组为一套黑色板岩、粉砂岩夹细砂岩地层组合,具陆相沉积特征。该套地层在原1∶20万区调工作中被划归索伦组(P_(1~s)),原1∶25万区调又将其划归哲斯组(P_(2~(zs))),本次将上部陆相碎屑岩部分重新厘定为上二叠统林西组。该地层的重新厘定对本区寻找烃源岩有重要的指导意义。     

The geochemical nature of the Archean Ancient Gneiss Complex and Granodiorite Suite,Swaziland: a preliminary study

The Ancient Gneiss Complex (AGC) of Swaziland, an Archean gray gneiss complex, lies southeast and south of the Barberton greenstone belt and includes the most structurally complex and highly metamorphosed portions of the eastern Kaapvaal craton. The AGC is not precisely dated but apparently is older than 3.4 Ga.The AGC consists of three major units: (a) a bimodal suite of closely interlayered siliceous, low-K gneisses and metabasalt; (b) homogeneous tonalite gneiss; and (c) interlayered siliceous microcline gneiss, metabasalt, and minor metasedimentary rocks — termed the metamorphite suite. A geologically younger gabbro-diorite-tonalite-trondhjemite suite, the Granodiorite Suite, is spatially associated with the AGC and intrusive into it.The bimodal suite consists largely of two types of low-K siliceous gneiss: one has SiO₂ < 75%, Al₂O₃ > 14%, low Rb/Sr ratios, and depleted heavy rare earth elements (REE's); the other has SiO₂ > 75%, Al₂O₃ < 13%, high Rb/Sr ratios, and relatively abundant REE's except for negative Eu anomalies. The interlayered metabasalt ranges from komatiitic to tholeiitic compositions. Lenses of quartz monzonitic gneiss of K₂O/Na₂O close to 1 form a minor part of the bimodal suite. Tonalitic to trondhjemitic migmatite locally is abundant and has major-element abundances similar to those of non-migmatitic varieties.The siliceous gneisses of the metamorphic suite show low Al₂O, K₂O/Na₂O ratios of about 1, high Rb/Sr ratios, moderate REE abundances and negative Eu anomalies.K/Rb ratios of siliceous gneisses of the bimodal suite are very low (～130); of the tonalitic gneiss, low (～225); of the siliceous gneiss of the metamorphite suite, moderate (～300); and of the Granodiorite Suite, high (～400).Rocks of the AGC differ geochemically in several ways from the siliceous volcanic and hypabyssal rocks of the Upper Onverwacht Group and from the diapirs of tonalite and trondhjemite that intrude the Swaziland Group.     

北祁连东段景泰地区下古生界两套砂岩微量元素和稀土元素特征及其构造意义

早奥陶世和早志留世是北祁连加里东造山带构造演化和盆地转变的关键时期。在造山带东段景泰地区,下奥陶统阴沟组和下志留统肮脏沟组两套砂岩的微量元素和稀土元素特征显示,阴沟组杂砂岩样品（Cj1和Cj3）具有最小的Eu/Eu*及最大的Th/Sc和REE,肮脏沟组杂砂岩具有较小的Eu/Eu*和较大的Th/Sc及REE;阴沟组岩屑砂岩样品（Cj13、Cj15和Cj18）具有最大的Eu/Eu*及最小的Th/Sc、REE和La/Yb。多个物源、构造背景判别图解和多元素蛛网图分析表明,阴沟组杂砂岩样品具大陆边缘的构造背景,主要物源为大陆上地壳再旋回沉积物和长英质岩石;岩屑砂岩样品为岛弧构造背景,以中基性安山质岩石为主要物源,可能受陆源物质的微弱影响。肮脏沟组杂砂岩构造背景复杂,表现出大陆岛弧、活动陆缘和被动陆缘三种环境共存的特点,受中基性火山弧物质、长英质岩石和再旋回沉积岩的混合物源的影响。两套砂岩的元素特征表明二者可能具有相似的源区。阴沟组杂砂岩源区可能为阿拉善地块南缘海原群变沉积岩或其他相似的陆源再旋回沉积物,砂岩碎屑以来自初始火山弧物质为主,以石灰沟岛弧型中基性火山岩作为其源岩最合适。阴沟组形成于初始弧后盆地环境,是岛弧活动的直接记录。肮脏沟组可能的源岩为阿拉善地块南缘海原群变沉积岩和中高等成熟度的石灰沟岛弧型火山岩及海原群岛弧型变火山岩,沉积于弧后前陆盆地,对构造环境的反映存在滞后性。     

Petrographical and geochemical signatures of Jurassic rocks of Chari Formation,Western India: implications for provenance and tectonic setting

The sandstones of the Ridge and Athleta members of Chari Formation (Callovian-Oxfordian) exposed at Jara have been analyzed for their petrographical and geochemical studies. Texturally, these sandstones are medium to coarse grained, poorly to well sorted, sub-angular to sub-rounded, and show low to medium sphericity. These sandstones were derived from a mixed provenance including granites, granite-gneisses, low and high-grade metamorphic, and some basic rocks of Aravalli range and Nagarparkar massif. The petrofacies analysis reveals that these sandstones belong to the continental block and recycled orogen tectonic regime. The studied sandstones are modified by paleoclimate, distance of transport, and diagenesis. Mineralogically and geochemically, sandstones are classified as quartzarenite, subarkose, arkose, sublithic arenite, and wacke, respectively. The A-CN-K ternary plot and CIA, CIW, PIA, and ICV values suggest that the similar source rocks suffered moderate to high chemical weathering under a hot-humid climate in an acidic environment with higher \({\text{P}}_{{{\text{CO}}_{ 2} }}\). Generally good to strong correlations between Al₂O₃ and other oxides in these sediments indicate clay mineral control. The K₂O/Na₂O versus SiO₂ diagram indicates that the studied samples occupy passive margin fields but the SiO₂/Al₂O₃ versus K₂O/Na₂O plot suggests that the Athleta Sandstone and Ridge Sandstone fall within the passive margin field, while Ridge Shale falls within the active continental margin field.     

Geochemistry of Carboniferous Sandstones (Sardar Formation), East‐Central Iran: Implication for Provenance and Tectonic Setting

Geochemical analysis of sandstones from the Sardar Formation (from two stratigraphic successions) in east-central Iran were used for identification of geochemical characterization of sandstones, provenance and tectonic setting. Sandstones in the two lithostratigraphic successions have similar chemical compositions suggesting a common provenance. Bulk-rock geochemistry analysis of Carboniferous sandstones from Sardar Formation indicates that they are mainly quartz dominated and are classified as quartzarenites, sublitharenites and subarkoses, derived from acid igneous to intermediate igneous rocks. Discrimination function analysis indicates that the sandstones of Sardar Formation were derived from quartzose sedimentary provenance in a recycled orogenic setting. Also, major and trace elements in sandstones of Sardar Formation (e.g., K2O/Na2O vs. SiO2) indicate deposition in a stable passive continental margin (PM). Chemical index of alteration (CIA) for these rocks (> 65%) suggests a moderate to relatively high degree of weathering in the source area.     

羌北-昌都地块那益雄组火山岩锆石U-Pb年代学及地球化学特征

本文对青藏高原羌北-昌都地块阿布日阿加措地区的晚二叠世那益雄组火山岩进行了年代学和地球化学研究。该火山岩主要由玄武岩、安山玄武岩、安山岩、流纹岩、凝灰岩组成,具有碱性玄武岩到酸性熔岩的特征。锆石U-Pb年代学研究表明该火山岩的形成时代为251. 1±4. 8～249. 6±1. 3 Ma之间。地球化学分析结果表明,该地区的流纹岩具有高的Si O2(74. 85%～77. 55%)和Na2O+K2O(5. 40%～6. 61%)含量,较低的MgO、K2O和Ca O含量,Al2O3含量低且稳定,里特曼指数平均为1. 15,小于3. 3。安山岩Si O2含量55. 13%～56. 28%,Na2O+K2O含量4. 13%～6. 15%,里特曼指数平均为2. 20,小于3. 3,属于钙碱性安山岩。碱性玄武岩Si O2含量51. 49%,Na2O+K2O含量6. 34%,里特曼指数为4. 73,属于碱性系列。稀土元素配分曲线为富集LREE的右倾型。另外,富集大离子亲石元素(LILE) Th、U,亏损高场强元素(HFSE) Nb、Ta等特征,均说明羌北-昌都地块阿布日阿加措地区的火山岩形成于陆缘岛弧环境。     

湖南常宁县康家湾铅锌金矿硅化角砾岩岩石地球化学特征

湖南常宁县康家湾铅锌金矿床硅化角砾岩带由未硅化角砾岩—极弱硅化角砾岩—硅化角砾岩—强硅化角砾岩(似硅质岩)组成,产于侏罗系与下伏二叠系间的不整合面附近,角砾成份复杂,充填物和胶结物类型多样。随着硅化程度的加强,硅化角砾岩带SiO₂含量变化大,最高可达95.34%,而Al₂O₃、MgO、FeO、K₂O、Na₂O、CaO、CO₂和P₂O₅含量特别是MgO、CaO、CO₂和P₂O₅含量明显降低,且K₂O>Na₂O,TiO₂的含量显著偏低。硅化角砾岩带LREE/HREE比值为1.95～4.93,Ce(δCe=0.44～0.81)和Eu(δEu=0.58～0.89)均为弱负异常,属轻稀土富集型,但随硅化程度增高稀土元素含量显著减少:未硅化和弱硅化角砾岩稀土元素总量较高,为(176.82～318.93)×10^-10,与当冲组泥质岩配分曲线相似;硅化强烈的角砾岩稀土元素总量低,为(7.71～65.95)×10^-10,与下伏栖霞组灰岩稀土元素配分曲线极为相似。结合微量元素F、Ba、Cl、Cr、Ni、Sr、V研究结果及硅化角砾岩带自底部至顶部特有的下粗上细的韵律性层理构造,认为康家湾铅锌金矿床硅化角砾岩带是在地台体制向地洼体制转变期的大地构造环境下,由于地壳快速隆升,二叠纪灰岩、泥质岩、石英砂岩等岩石剥蚀,在古河流环境下搬运、沉积形成的。此     

北天山东段阿奇山组火山岩的地球化学特征及锆石U-Pb年龄

阿奇山组分布于北天山东段觉罗塔格构造带内部的雅满苏岛弧带中,属于原雅满苏组下部的火山岩部分,而上部火山岩则属于土古土布拉克组。在阿奇山地区,阿奇山组由中-酸性火山岩、火山碎屑岩和火山碎屑沉积岩组成。岩石地球化学特征显示为钙碱性岛弧火山岩系列,火山岩主体具有高Sr、Na₂O、Al₂O₃、SiO₂, 低MgO、Y、Yb,及明显亏损HFSE、Nb、Ta等特征,与经典埃达克岩地球化学特征吻合,Nb、Sr、Sr/Y值显示为俯冲型埃达克岩。地球化学相关图解等表明岩浆同化混染作用弱、经历了辉石、斜长石、钛铁氧化物和磷灰石的分离结晶作用、且部分熔融发生在石榴石稳定域。与东部土屋-雅满苏地区阿奇山组火山岩的对比研究表明,东部地区的火山岩不具埃达克岩特征,说明埃达克岩分布的局限性。锆石U-Pb SHRIMP 谐和年龄为341.7±2.7Ma,与首次在该组中采集的化石资料完全一致,代表了火山岩的形成年龄。与其北部大南湖岛弧带中的小热泉子组、企鹅山组形成年龄（325.1±3.2Ma、322.6±2.0Ma）对比研究暗示,准噶尔板块南缘石炭纪存在构造-岩浆活动随时间由南向北迁移。     

Geochemical characteristics of sandstones from Cretaceous Garudamangalam area of Ariyalur,Tamilnadu, India: Implications of provenance and tectonic setting

The Trichinopoly Group (later redesignated as Garudamangalam) has unconformable relationship with underlying Uttatur Group and is divided into lower Kulakanattam Formation and upper Anaipadi Formation. These calcareous sandstones are analysed major, trace and rare earth elements (REEs) to find out CIA, CIW, provenance and tectonic setting. The silica content of fossiliferous calcareous sandstone show wide variation ranging from 12.93 to 42.56%. Alumina content ranged from 3.49 to 8.47%. Higher values of Fe₂O₃ (2.29–22.02%) and low MgO content (0.75–2.44%) are observed in the Garudamangalam Formation. CaO (23.53–45.90) is high in these sandstones due to the presence of calcite as cementing material. Major element geochemistry of clastic rocks (Al₂O₃ vs. Na₂O) plot and trace elemental ratio (Th/U) reveal the moderate to intense weathering of the source rocks. The Cr/Zr ratio of clastic rocks reveal with an average of 1.74 suggesting of felsic provenance. In clastic rocks, high ratios of \(\sum \)LREE/\(\sum \)HREE, La/Sc, Th/Sc, Th/Co, La/Co and low ratios of Cr/Zr, and positive Eu anomaly ranges from (Eu/Eu* = 1.87–5.30) reveal felsic nature of the source rocks.