LA-ICP-MS U–Pb geochronology of detrital zircons from the Zhaochigou Formation-complex in the Helan Mountain and its tectonic significance

This paper carries out studies about LA-ICPMS U–Pb dating and Hf isotopic compositional analysis for detrital zircons in two metasedimentary samples that were taken from the Zhaochigou Formation-complex in the Helan Mountain.The results show that the Zhaochigou Formation-complex formed*1.96 Ga,and it is a part of the Khondalite Series that is widespread in the North China Craton(NCC).The age spectrum of the detrital zircons indicates that the Zhaochigou Formation-complex shared the same provenance with the eastern edge of the Khondalite Series.Products of ancient magmatic activities within the Khondalite Belt may be the major source for the sedimentary materials that formed the Khondalite Series.Our age-dating results suggest that the Khondalite Series in the NCC may have experienced two stages of metamorphism,as the early stage occurred during 1.96–1.95 Ga,and the later stage occurred at about 1.87 Ga.The Hfisotopic data indicate that the Western Block of the NCC endured a stage of crustal growth at 2.5–2.3 Ga.     

江西会昌盆地埃达克质粗面岩年代学、地球化学与成因研究

江西是华南白垩纪红色碎屑沉积岩系最发育的地区之一,且常夹有火山岩层。会昌岽背村一带红色沉积岩系底部的火山岩具有较高Si O2和Al2O3,较低的Mg O,Si O2=59.0%~64.6%(平均61.9%),Al2O3=15.5%~18.9(平均17.7%),Mg O=0.28%~0.92%(平均0.55%);富碱和钠,(Na2O+K2O)=7.19%~10.1%(平均9.70%),Na2O=6.50%~7.70%(平均7.03%),在Si O2-(Na2O+K2O)图解上落入碱性系列粗面岩或粗面英安岩范围;CIPW计算结果显示,标准矿物Ab=57.2%~65.7(平均60.5%),Q=6.07%~14.7%(平均9.95%),小于20%,属粗面岩。稀土总量较低,轻稀土明显富集,重稀土强烈亏损,Eu负异常不明显,∑REE=114×10-6~168×10-6,∑LREE=101×10-6~148×10-6,∑HREE=14.9×10-6~19.6×10-6,∑LREE/∑HREE=6.54~7.52,(La/Yb)N=24.9~34.2(平均27.4),δEu=0.81~1.10(平均0.98%),在稀土曲线图上呈明显的右倾,具高压型粗面岩的特征。较低的Y和Yb含量,较高的Sr含量和Sr/Y比值,Y=8.99×10-6~11.7×10-6(平均10.8×10-6),Yb=0.55×10-6~0.82×10-6(平均0.7×10-6),Sr=329×10-6~836×10-6(平均498×10-6),Sr/Y=36.5~71.8(平均48.2),具有埃达克岩的特征;在不相容元素蛛网图上显示富集大离子亲石元素(Cs,Rb,Ba,K等元素),强烈亏损高场强元素(Ta、Nd),具壳源的特征。较低的(87Sr/86Sr)i值、较高的εNd(t)和较小的TDM2值,(87Sr/86Sr)i=0.7074~0.7082(平均0.7077),εNd(t)=-1.99~-2.60(平均-2.29),TDM2=1 071 Ma~1 120 Ma(平均1094 Ma),具年轻下地壳部分熔融产物的特征。SHRIMP锆石U-Pb测年结果显示,14个分析点的206Pb/238U年龄变化范围为(114~108)Ma,加权平均年龄为(110.7±1.0)Ma,MSWD=0.47,指示地质时代属早白垩世晚期。上述特征显示,会昌岽背村一带红色沉积岩系底部的火山岩为早白垩世晚期加厚地壳背景下年轻下地壳部分熔融形成的埃达克质粗面岩。     

新疆巴伦台钾长花岗岩的地球化学及年代学

目的探究新疆中天山巴伦台地区钾长花岗岩的地球化学特征、成岩年龄及其地质意义。方法在详细的地质调查基础上,分析其主量、微量元素含量等地球化学特征,并利用锆石LA-ICP-MS U-Pb定年方法确定其成岩年龄。结果钾长花岗岩具有火山弧花岗岩特征,形成年龄为369.6 Ma±2.6 Ma。结论古生代南天山洋洋壳向伊犁—中天山微板块下的俯冲至少延续到晚泥盆世。     

EPC用锆英粉涂料的研制

以超细锆英粉作为耐火骨料,配制EPC用锆英粉涂料。测试涂料的密度、悬浮性、涂层强度、涂层厚度、透气性五种性能,并通过浇注实验,由铸件成型、铸件表面以及涂层残片来分析改进后涂料的使用效果,获取最佳超细锆英粉涂料。     

～4.1 Ga xenocrystal zircon from Ordovician volcanic rocks in western part of North Qinlin80rosenic Belt

High-precision U-Pb dating by in situ LA-ICP-MS yields an age of 4079±5 Ma for a xenocrystal zircon from Ordovician volcanics of the Caotangou Group in western part of the North Qinling Orogenic Belt. As a result, the North Qinling Orogenic Belt becomes one of a few localities in the world that contain Hadean age records （4276±6 Ma and 4404±8 Ma detrital zircons from Jack Hill of the Yilgarn craton, 4016 Ma Acasta gneisses of the Wopmay Orogeny and Burang quartzite with detrital zircon of 4103 Ma in Tibet）. It is also the first report of the Hadean age in Phanerozoic volcanics. The finding of the 4.1 Ga xenocrystal zircon provides not only the geochronological record of the oldest crustal materials in China, but also the condition for further search for rocks forming in the region during the early time of the Earth＇s evolution. Thirty-six zircon U-Pb dates from the Ordovician volcanic rocks are subgrouped into seven generations that represent different tectono-magmatic events in the North Qinling Orogenic Belt. Among them, two periods of 0.9--1.5 Ga and 0.4--0.5 Ga are consistent with Mesoproterozoic and Early Paleozoic orogenies, respectively.     

山东金城地区焦家断裂带下盘隐伏花岗岩类岩石地球化学特征及锆石U-Pb年龄

胶西北金矿集区内中生代花岗岩类分布广泛,与区内金矿成矿关系密切。焦家断裂带深部下盘隐伏的岩体岩性以花岗岩类为主,其成岩时间及成因分类尚存在争议,本次在金城地区采取深部花岗岩类样品,开展了锆石U-Pb测年、主微量元素等测试工作,对花岗岩的岩相学特征、形成时间、岩石地球化学特征等进行了研究。金城地区焦家断裂带下盘深部花岗岩类为中生代侏罗纪玲珑型花岗岩（测得锆石U-Pb年龄值为158.4Ma和160.4Ma）和白垩纪郭家岭型花岗岩。本次研究花岗岩样品均表现为I型花岗岩的地球化学特征,说明玲珑型花岗岩重熔物质较复杂,若重熔地壳源岩为火成岩表现为I型花岗岩的特征,重熔的地壳源岩为表壳岩类,则表现为S型花岗岩的特征。区内中生代花岗岩类的形成与太平洋板块俯冲华北板块有关,属大陆弧花岗岩类,为火山弧构造环境。     

中新生代天山板内造山带隆升证据：锆石、磷灰石裂变径迹年龄测定

取自天山南侧库车盆地北缘欧西达坂花岗岩体的锆石、磷灰石裂变径迹年龄给出了初步结果：中 新生代天山板内造山带在早白垩世（134Ma～109Ma）发生了明显快速隆升,平均隆升速率为0.13mm/a（130m/Ma）;而从晚白垩世到现在,天山板内造山带的平均隆升速率为0.03mm/a（31.9m/Ma）。在晚新生代天山板内造山带再次发生了快速隆升。现有的同位素研究成果表明中新生代天山造山带至少发生了两次幕式快速隆升。     

Zircon LA-ICPMS study and petrogenesis simulation of Dahuabei pluton in the Wulashan area,Inner Mongolia

Dahuabei pluton in the Wulashan area,Inner Mongolia,is an alkaline and peraluminous granitic pluton.LA-ICPMS U-Pb dating of zircons indicates that this pluton crystallized at 330±10 Myr.The pluton did not experience apparent zircon fractionation.The consistent temperatures between Zr saturation (765℃) and the average zircon-rutile Ti equilibrium (780℃),together with zircon ages and their CL images,indicated that there were no inherited zircons in this pluton.Through the simulation of the dry-system crystallization process of magma cooling at 200 MPa and 1100-709℃,the phase diagram and composition evolution tendency of different phases were obtained.The magma reached its liquidus at 1069℃.Sanidine was the first crystallized phase;at 709℃ the residual magma was less than 4%,and the range of 1069-719℃ should be the most suitable approach to the real condition.It is shown that at least some part of the pluton underwent such isobaric equilibrium crystallization processes during its crystallization.     

冀北凤山晚古生代闪长岩-花岗质岩石的成因:岩石地球化学、锆石U-Pb年代学及Hf同位素制约

冀北凤山地区侵位于前寒武纪岩石组合中的晚古生代的闪长岩-花岗质岩石,具有富Na,高Sr,低Y和重稀土元素等地球化学特征,Sr/Y在37.15～151.22之间变化,绝大多数样品均显示正Eu异常(一个样品例外),Eu·在0.92～1.53之间变化.LA-ICP-MS锆石U-Pb同位素测年和锆石Hf同位素分析表明闪长岩(JB6024)和二长花岗岩(样品JB6037-1)分别形成于315±2.8Ma和306.6±6Ma,即该区晚古生代存在两个岩浆作用幕.地球化学、全岩Sr-Nd同位素和锆石Hf同位素研究揭示凤山晚古生代闪长岩是EMI型富集岩石圈地幔部分熔融形成的岩浆与古老下地壳部分熔融形成的长英质岩浆混合作用结果,而花岗质岩石则是闪长质岩浆发生分离结晶作用的残余岩浆同化上部地壳岩石形成的.     

江南隆起（九岭）多阶段构造演化的花岗岩记录

以江南隆起九岭花岗岩体为研究对象,应用激光剥蚀等离子体质谱(LA-ICP-MS)锆石U-Pb定年技术,得到该花岗岩侵入年龄为853～811Ma.自晋宁期以来,九岭地区依次经历了加里东、印支及燕山等多阶段构造演化.通过花岗岩地球化学及构造图解分析,可知江南隆起九岭多阶段构造演化环境各不相同.晋宁期(929-810 Ma)花岗岩体落入岛弧与碰撞的过渡环境;而加里东期(439-411 Ma)花岗岩体具板内汇聚环境特点;燕山期(158-118 Ma)花岗岩形成于同碰撞兼火山弧构造环境.