西秦岭西段塔洞花岗闪长岩体年代学、地球化学特征及其地质意义

塔洞花岗闪长岩体位于西秦岭造山带西段,主体岩性为灰白色中细粒块状花岗闪长岩,岩体中未见暗色闪长质包体。对该岩体进行LA-ICP-MS锆石U-Pb同位素年代学测试,所选锆石均为具岩浆韵律环带结构的岩浆锆石,锆石w(Th)/w(U)值主体大于0.4,锆石U-Pb加权平均年龄为(219.0±5.3)Ma,代表塔洞花岗闪长岩体的结晶年龄。地球化学特征显示,该岩体具有高SiO2质量分数(66.88%~67.46%)、高Al2O3质量分数(15.39%~16.54%)、富K(质量分数为2.83%~4.12%)、准铝质(A/CNK值介于0.97~1.0之间)的高钾钙碱性花岗岩特征。该岩体轻、重稀土元素分异强烈,Eu异常不明显,球粒陨石标准化稀土元素配分模式为右倾型,原始地幔标准化微量元素蛛网图具明显的富集大离子亲石元素(Cs、Rb、Ba等),亏损重稀土元素与高场强元素(如Nb、Ta等)的特征。该岩体具有与埃达克质花岗岩相似的特征,如高Sr质量分数(主体大于400×10-6)、低Y质量分数((5.49~12.8)×10-6)、低Yb质量分数((0.34~0.91)×10-6)、高w(Sr)/w(Y)值(大于40,多介于50~90之间)。岩石成因研究表明,该岩体为加厚下地壳石榴子石角闪岩(石榴子石体积分数为10%~20%)部分熔融并经历分离结晶作用形成的。综合区域资料认为,西秦岭造山带西段古特提斯洋于印支晚期已经关闭,南北陆块完成同碰撞造山作用,并进入后碰撞构造演化阶段。     

西秦岭天水地区早中生代草川铺花岗岩年代学、地球化学特征及其地质意义

西秦岭天水地区早中生代草川铺岩体内发育一套似斑状花岗岩,岩体主要由寄主似斑状二长花岗岩及闪长质微粒包体组成。SHRIMP锆石U-Pb定年结果显示,寄主岩体的侵位年龄为(210.9±1.7)Ma,平均标准权重偏差(MSWD)为1.74,属于早中生代花岗岩体。岩石地球化学研究表明:寄主岩体属于高钾钙碱性系列,具准铝质特征,A/CNK值为0.99~1.07;稀土元素总质量分数为(128.13~196.56)×10-6,轻、重稀土元素质量分数比值为8.20~9.47,岩体富集轻稀土元素,微量元素特征表现为高场强元素贫化,但元素Ta、Nb明显亏损。岩相学、地球化学和年代学特征表明,早中生代草川铺岩体与南秦岭糜署岭岩体具有相似的岩相学特征和近一致的结晶年龄,并且二者的稀土、微量元素特征相似。因此,早中生代草川铺岩体和糜署岭岩体是同一套岩浆活动的产物,前者虽然构造位置处于北秦岭造山带内,但其物质来源于南秦岭造山带,表明南秦岭造山带和北秦岭造山带在晚三叠世之前已经碰撞。由于早中生代草川铺岩体具高钾钙碱性埃达克岩地球化学特征,所以其是南秦岭造山带向北秦岭造山带俯冲熔融的产物。     

佳木斯地块中部晚三叠世埃达克岩年代学、地球化学特征及其地质意义

大八浪岩体位于佳木斯地块中部的桦南隆起区,岩性为中细粒黑云母花岗闪长岩,其侵入到晚二叠世白云母二长花岗岩中。岩石LA-ICP-MS锆石U-Pb年龄为(234±1)Ma,属于晚三叠世早期。大八浪岩体具有较高的SiO₂含量(质量分数,下同)(62.04%～64.30%)、Al₂O₃含量(15.68%～16.95%)、Sr/Y值(23.38～36.15)、(La/Yb)_N值(18.57～33.04),较低的MgO含量(0.91%～1.20%)和中等Mg^#值(34.03～37.27),以及低Yb含量((1.18～1.52)×10^-6,平均值为1.30×10^-6)、Y含量((15.43～20.50)×10^-6,平均值为16.94×10^-6),同时Na₂O/K₂O值为0.77～1.06,平均值为0.94,显示与C型埃达克岩相似的地球化学特征。结合佳木斯地块东缘...     

西秦岭多哇地区萨日加岩体LA-ICP-MS锆石U-Pb年龄、地球化学特征及其地质意义

西秦岭造山带发育大量的印支期高钾钙碱性花岗岩,它们的成岩时代和岩石成因对认识西秦岭岩浆活动和构造演化具有重要意义。对西秦岭多哇地区萨日加岩体进行了详细的野外地质调查、岩相学观察、LA-ICP-MS锆石U-Pb定年和全岩地球化学研究,旨在查明该岩体的年龄、成因类型以及成岩地球动力学背景。结果表明:萨日加岩体由英安斑岩、花岗斑岩及少量石英闪长岩组成;花岗斑岩LA-ICP-MS锆石U-Pb年龄为(238.2±2.6)Ma(平均标准权重偏差(MSWD)为1.7);萨日加岩体属于过铝质高钾钙碱性岩石系列,富集大离子亲石元素Th、Rb、K和轻稀土元素,亏损高场强元素Nb、Ta、Ti等,指示其岩浆源区具有壳幔混合的特征;岩石的主量、微量元素特征显示,英安斑岩属于I型花岗岩,形成于洋-陆俯冲岛弧环境;花岗斑岩倾向于S型花岗岩,形成于大陆碰撞构造环境。由此认为,萨日加岩体形成于晚三叠世西秦岭由洋-陆俯冲岛弧向陆-陆碰撞转变的构造环境。     

东昆仑五龙沟金矿田平台岩体岩相学、年代学、地球化学特征及其构造意义

东昆仑五龙沟金矿田东南部出露中三叠世侵入体——平台岩体,为探究古特提斯洋俯冲演化过程提供了新的线索。对平台岩体内的花岗闪长岩开展了详细的岩相学、LA-ICP-MS锆石U-Pb年代学、岩石地球化学和Hf同位素研究。结果表明：平台岩体内的花岗闪长岩主要由斜长石(体积分数为45%～50%)、石英(20%～25%)、钾长石(20%～25%)、角闪石(5%)、黑云母(5%)组成;花岗闪长岩锆石U-Pb加权平均年龄为(247±1)Ma,侵位于中三叠世;主量元素特征显示SiO₂含量(质量分数)为64.88%～65.90%, FeO^T/MgO平均值为3.70,Fe₂O₃/FeO平均值为1.48,锆石饱和温度平均值为770℃,因此,花岗闪长岩属于I型花岗岩;球粒陨石标准化稀土元素配分模式表现为轻稀土元素富集、重稀土元素亏损的特征,并具有弱负Eu异常;原始地幔标准化微量元素蛛网图具有富集大离子亲石元素(Cs、Rb、Ba)、亏损高场强元素(Nb、Ta等)的特征;花岗闪长岩的锆石ε_Hf(t)值为-4....     

滇西哀牢山构造岩浆岩带阿扎鲁花岗岩岩石地球化学特征及构造背景浅析

阿扎鲁岩体分布于哀牢山构造岩浆岩带中,通过野外地质调查与岩体剖面测量、岩石样品采集分析、薄片显微镜下鉴定等手段与方法,对其野外地质特征、岩石学特征及岩石地球化学特征进行了系统研究,并探讨了其形成的构造环境。研究结果表明,阿扎鲁岩体的岩性为花岗岩,岩体分布明显受断裂控制;岩石局部可见后期变质的片岩及糜棱岩,岩石具浅层侵入的特点;阿扎鲁花岗岩的A/NCK多大于1.0,为铝饱和型;具有富硅钾、低钙、贫铁、镁、钛的特点,岩石为高钾钙碱性系列。其主量元素、微量元素及稀土元素地球化学特征均表明,该岩体形成于造山期碰撞后期的弧陆碰撞阶段。      

安徽南陵—宣城地区岩浆岩锆石U-Pb年龄及元素地球化学特征

安徽南陵-宣城地区是一个中-新生代火山-沉积盆地,位于长江中下游构造-岩浆-成矿带东北段的东南翼。对该区发育的岩浆岩开展了较为系统的LA-ICP-MS锆石U-Pb定年及岩石主量、微量和稀土元素分析,并与长江中下游构造-岩浆-成矿带其他地区岩浆岩进行对比,旨在确定岩浆岩的成岩时代、探讨岩浆岩成因及其与成矿的关系。南陵-宣城地区岩浆岩一部分侵入于盆地基底中,另一部分喷发形成盆地盖层,还有一部分产于盆地之上的推覆构造(体)中。侵入岩的岩性主要为花岗岩、花岗闪长岩、石英闪长岩、辉石闪长岩等,火山岩主要为英安质火山碎屑岩和熔岩。获得的侵入岩锆石U-Pb年龄主要为138~135 Ma,火山岩年龄均小于134 Ma,表明岩浆作用发生于晚中生代(燕山晚期)早白垩世。岩浆岩主量元素显示高Si、K的特征,为亚碱性高钾钙碱性系列岩石;微量元素组成显示岩浆岩富集Rb、Th、U、K等大离子亲石元素,亏损Nb、Ta、Ti等高场强元素,火山岩比侵入岩较为亏损Sr和P;球粒陨石标准化稀土元素配分模式均表现为富集轻稀土元素的右倾模式和较弱的Eu负异常。元素地球化学特征指示区内岩浆岩具有壳幔混源且以幔源为主的特征。南陵-宣城地区既发育与长江中下游构造-岩浆-成矿带隆起区(如铜陵地区)同位素地质年龄和地球化学特征基本一致的侵入岩,又发育与凹陷区(如庐枞、宁芜等盆地)同位素地质年龄和地球化学特征基本一致的火山-次火山岩,显示该区晚中生代岩浆作用具有长江中下游构造-岩浆-成矿带隆起区和凹陷区的双重特征。岩浆作用的双重特征暗示与其有关的成矿作用也可能具有双重性,即既可能发育与隆起区侵入岩浆作用有关的斑岩型、矽卡岩型和脉型铜金等多金属矿床,也可能发育与凹陷区火山-次火山岩有关的玢岩型铁(硫)矿床。     

内蒙古东乌旗巴彦都兰二长花岗岩年代学、地球化学特征及其地质意义

为了解晚古生代西伯利亚板块南缘增生造山过程中的岩浆活动特征,对东乌旗巴彦都兰二长花岗岩岩相学、锆石U-Pb年代学、锆石Hf同位素和岩石地球化学进行了研究,并讨论了岩石成因和构造环境。锆石LA-ICP-MS U-Pb定年结果为(277.2±0.7)Ma,以正的锆石ε_Hf(t)(6.8~14.1)为特征,具有年轻的锆石地壳模式年龄(tc_DM)(865~655 Ma),属于早二叠世晚期岩浆活动产物。二长花岗岩以高钾[w(K)=3.63%~4.95%,K₂O/Na₂O=0.91~1.47]、富碱[w(K₂O+Na₂O)=7.52%~9.16%]、准铝质-弱过铝质(A/CNK=0.96~1.15)为特征;稀土元素总量较低(38.82×10-6~193.20×10-6),(La/Yb)_N为3.91~23.08,轻、重稀土元素分异较明显,呈弱负铕异常(δEu为0.34~1.17);富集部分大离子亲石元素(LREE、Rb、K等);Zr弱负异常、Hf弱正异常,亏损Sr、Nb、Ta、P、Ti,显示后造山花岗岩特征。综合分析表明,巴彦都兰二长花岗岩形成于伸展的构造环境中,是贺根山洋盆闭合后的后造山阶段产物,为865~655 Ma前洋壳俯冲形成的先成地壳部分熔融而成。      

内蒙古德言其庙斜长角闪岩系年代学、地球化学特征及其地质意义

德言其庙斜长角闪岩系位于内蒙古中部温都尔庙地区以东,构造位置处于华北板块北缘温都尔庙俯冲-增生杂岩带内。对德言其庙斜长角闪岩系进行了地球化学分析和锆石SHRIMP UPb定年。结果表明:斜长角闪岩系SiO2质量分数为51.62%~55.60%,Al2O3为16.45%~17.78%,全碱质量分数(4.5%~5.12%)较低;斜长角闪岩系具有钙碱性系列岩石地球化学特征,原岩为辉长质和辉长闪长质侵入岩;锆石n(206 Pb)/n(238 U)年龄加权平均值为(490.3±4.6)Ma;岩石富集轻稀土元素,轻、重稀土元素质量分数比值为5.93~7.73,Eu异常(0.84~1.05)不明显,具有明显的Nb、Ta负异常及Ti、P亏损,显示出其原岩具有消减带岩浆的特征,形成于岛弧构造环境。     

准噶尔盆地东北缘卡拉麦里花岗质岩体年代学、地球化学特征及铀成矿潜力

准噶尔盆地东北缘卡拉麦里地区发育大量花岗质岩体,岩性主要为碱长花岗岩,以及少量石英二长岩和二长花岗岩。以上述3种岩体为研究对象,进行了锆石U-Pb年代学、Hf同位素和岩石地球化学研究。花岗质岩体LA-ICP-MS锆石U-Pb年龄为325～308 Ma,形成时代为晚石炭世。岩石地球化学特征显示其属于准铝质—弱过铝质高钾钙碱性系列,具有高Si、富碱、富K、富Al等特点。碱长花岗岩具有A型花岗岩特征,而石英二长岩和二长花岗岩具有I型花岗岩特征。卡拉麦里晚石炭世花岗质岩体所处构造背景应为由挤压碰撞到拉张的转换时期。物源分析表明：铀矿的铀源来自卡拉麦里花岗质岩体,U含量平均值超过3×10^-6,Th/U平均值为7.18,具备富铀地质体特征,U迁移量可高达8.26×10^-6,U平均原始含量为5.46×10^-6;K₂O/Na₂O值为0.75～1.46,平均值为1.11,FeO/MgO值为1.18～20.73,平均值为5.28,显示其具有较高的陆壳成熟度,表明该地区具有较高的铀成矿潜力。     

Geochronology,geochemistry and Hf isotopic study of Early Carboniferous granodiorites in Taerqi region,central Daxing'anling and its tectonic implication

Zircon U-Pb age,whole rock geochemical and zircon Hf isotopic data are presented for Late Paleozoic granodiorites from the Taerqi region,central Daxing'anling to constrain its petrogenesis and tectonic implication.LA-ICP-MS zircon U-Pb age data indicates that the Late Paleozoic granodiorites were emplaced with age of333.4 ± 2.2 Ma(Early Carboniferous).Geochemically,the granodiorite samples have Si O2= 60.54%-71.40%,Na2 O = 4.04%--4.66%,K2 O = 1.65%--4.27% and Mg O = 0.96%--3.53%,belonging to medium-K to high-K calc-alkaline I-type granites.They are slightly enriched in large ion lithophile elements(e.g.Rb,Th,U and K) and light rare earth elements,and depleted in high field strength elements(e.g.Nb,Ta and Ti),with εHf(t) values of 8.0--11.8 and Hf two-stage model ages of 586-829 Ma.All these geochemical features suggest that the primary magma was derived from partial melting of Neoproterozoic to Phanerozoic newly accreted lower crust.According to the geochemical data and regional geological investigations,the Early Carboniferous granodiorites formed in an island arc setting linked to the subduction of the Paleo-Asian Oceanic Plate beneath the Xing'an Terrane.This also implies that the Xing'an and Songliao terranes have not amalgamated before the Early Carboniferous.     

Geochemistry and zircon U-Pb chronology of quartz porphyry in Yuejinshan Fe-polymetallic deposit of Heilongjiang

Quartz porphyry in Yuejinshan Fe-polymetallic deposit is one of the rock masses, which formed the granite belt relating to the late Yanshanian skarn-type Fe-polymetallic deposits in the eastern Heilongjiang, and is also closely related to the metallogenic space of the Fe-polymetallic deposits. Quartz porphyry has the zircon U-Pb concordia age of 125.0±1.1 Ma, overall showing high Si(SiO_2=74.48%--75.00%), rich alkaline(Na_2O+K_2O=7.93%--8.17%, K_2O/Na_2O=1.39--1.46), and poor Mg(MgO=0.27%--0.31%), with the A/CNK value being 0.95--0.99, having the characteristics of obvious enrichment of LREE and medium Eu negative anomaly(0.69--0.74), indicating that the rock belongs to quasi-aluminous high potassium calc-alkaline series and has the same characteristics as those of the I-type granite. The rock is also characterized by the enrichment of LILE and active incompatible elements, and depletion of HFSE such as Nb, Ta, P and Ti, with the Mg~# value being 32--37, indicating that the rock originated from partial melting of crustal materials. It can be concluded from the above characteristics or data and from the distribution of contemporary magmatic rocks in the area, that quartz porphyry in Yuejinshan Fe-polymetallic deposit was formed in a tectonic background of the subduction of the paleo-Pacific plate in late Yanshanian.     

Geochronology and geochemistry of Hutouya monzonitic granite of Qimantage,Qinghai

The geochemical features of the monzonitic granite in Qimantage Hutouya deposit area,Qinghai,in respect to the mineralization,suggest that this granite belongs to weak peraluminous and high-k calc alkaline rock series. The REE of the samples show right slope with obvious LREE/HREE differentiation and negative Eu abnormity. The trace elements show enrichment of LILE( Rb,Th,U,La,Nd),and deleption of Ba,Sr,Nd,P,Ti. The Sr-Nb isotopic data indicate that the magma source is mainly aluminosilicate lower crust with a small amount of new crustal materials. The weighted mean zircon U-Pbage of the Hutouya monzonitic granite is 221±1.7 Ma,belonging to Late Triassic. The Hutouya monzonitic granite was formed in the tectonic setting of transition from compression to extension during Middle-Late Triassic.     

沂水南小尧金矿锆石U-Pb同位素特征及其地质意义

沂水南小尧金矿产于沂沐断裂带汞丹山凸起上,赋矿围岩为古元古代花岗岩。通过对南小尧金矿矿石中的锆石采用LA—CPMS法进行单颗粒锆石微区U—Pb同位素年龄测定,获得锆石谐和年龄（2438±13）Ma的结果,为赋矿围岩的形成年龄;而下交点（116±20）Ma大致为金矿的形成年龄。结合南小尧金矿石中钾长石矿物K—Ar年龄为（94．29±1．38）Ma的结果分析。本区金矿的形成时代应在早白垩世中-晚期。     

新疆阿尔泰大喀拉苏花岗岩年代学、地球化学特征及其构造意义

大喀拉苏似斑状黑云母二长花岗岩出露于新疆阿尔泰南缘,是研究阿尔泰二叠纪构造环境的理想对象。采用LA-Q-ICP-MS锆石U-Pb定年获得其加权平均年龄为(261.4±2.1)Ma,属中二叠世。岩石具有高Si(SiO2质量分数为69.03%~70.94%)、富Al(Al2O3为14.18%~14.71%)、富K(Na2O/K2O值为0.70~0.87)的特征,A/CNK值为1.02~1.04,属高钾钙碱性弱过铝质花岗岩,显示I-A过渡型特点。微量元素表现出Rb、Th、Pb、Nd、Sm的相对正异常;Ti、P、Sr和Ba的负异常;稀土元素显示轻稀土元素强富集、重稀土元素平缓及明显的负Eu异常(0.55~0.82)。岩石的εNd(t)值和两阶段模式年龄分别为2.66~3.01和0.79~0.80Ga。综合区域地质资料和岩体地球化学特征,认为大喀拉苏黑云母二长花岗岩形成于后造山伸展环境,岩浆来源于地幔和地壳物质的混合,并在岩浆源区经历了分离结晶作用。     

东秦岭华县西沟钼矿床Re-Os同位素年龄及其地质意义

东秦岭华县西沟钼矿床位于华北陆块南缘老牛山岩体与华山岩体所夹持的EW向长廊中,产出于太古界太华群黑云斜长片麻岩地层内。该矿床已经被确定为中型矿床。西沟钼矿区内构造发育,岩浆活动强烈,展布的多条长石-石英脉、碳酸盐脉型钼矿体主要受近EW向剪切带控制,矿石类型以石英脉型、长石-石英脉型、方解石-石英脉型及蚀变岩型为主。应用Re-Os同位素地质年代学方法测得西沟钼矿床的成矿模式年龄为(206.7±2.8)~(214.7±2.8)Ma,等时线年龄为(212.4±2.8)Ma,属于印支晚期;辉钼矿Re质量分数为(306.6~401.0)×10-6,暗示成矿物质主要来源于上地幔。区域成矿条件对比发现,西沟钼矿床与黄龙铺钼矿床在成矿时代、成因类型等方面具有一致性,矿床类型划归为长石-石英脉、碳酸盐脉型。依据化探异常及初步勘查结果,预测西沟地区深部可能存在有隐伏岩体,具有寻找大型钼矿床的潜力。     

Zircon U-Pb geochronology and geochemistry of syenogranites in western Niubiziliang,northwestern Qaidam,Qinghai

The study presents the results of U-Pb dating of zircons and whole-rock geochemical analyses of a syenogranite located in the western Niubiziliang area,China with the aim of determining its formation time,petrogenesis and the regional tectonic setting. Zircons within the syenogranite are euhedral-subhedral and display rhythmic growth zoning,indicating a magmatic origin. Zircon U-Pb data obtained by LA-ICP-MS indicate the syenogranite formed in the Late Permian (260.7±1.5 Ma). The w(SiO_2) of syenogranites is 70.82%--73.59%,w(Al_2O_3) is 13.49%--14.82%,and w(Na_2O + K_2O) is 7.85%--8.52%,and yield K_2O/Na_2O ratios of 1.06--1.26. Therefore,the syenogranites belong to the high-K calc-alkaline and metaluminous (A/CNK 1,A/NK 1) series which display I-type granites similarly. The syenogranites also show the geochemical characteristics of volcanic arc rocks,being enriched in large-ion lithophile elements (LILEs; K,Rb) and light rare-earth elements (LREEs; La,Ce,Sm,Nd),but depleted in high field strength elements( HFSEs; Ta,Nb,P,Ti). On the whole,trace element ratios are close to the mean of the Earth's crust,indicating a lowercrust magma source. The low Sr (161--214) ×10~(-6) and Yb (1.08--1.80)×10~(-6) concentrations indicate that plagioclase and hornblende are residual mineral phases in the source. The regional geology and whole-rock geochemistry suggest that the formation of the syenogranites was related to subduction of the Zongwulong Ocean crust,and the north margin of Qaidam Block during the Late Permian was in an active continental margin tectonic setting.     

Zircon U-Pb geochronology,geochemistry and petrogenesis of syenogranite from Angeer Yinwula area in Inner Mongolia

The study presents the results of U-Pb dating of zircons and whole-rock geochemical analyses of syenogranite in Angeer Yinwula area, China, with the aim of determining its formation time, petrogenesis and regional setting. Zircon U-Pb data obtained by LA-ICP-MS indicate that the syenogranite formed in the Early Cretaceous(136.1±0.9 Ma). Geochemically, the rock is characterized by high SiO_2(76.63%--77.58%) and Na_2O+K_2O(8.00%--8.32%), low MgO(0.02%--0.04%) and TFe_2O_3(0.51%--0.84%), and is enriched in LREEs and LILEs, depleted in HREEs and HFSEs. It belongs to high-K calc-alkaline, metaluminous-weakly peraluminous, exhibiting an affinity to I-type granite. All these characteristics implied that the syenogranite in this region derived from crust-mantle mixed source. Overall, the regional geology, geochronology and geochemical features suggest that the formation of the syenogranite was related to the subduction of the Paleo-Pacific Ocean.