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531.
浙江是非金属矿大省,金属矿特别是斑岩型矿床的研究亟待进行。本文以里山岭斑岩型铜矿床为研究对象,首次采用SHRIMP U-Pb对该岩体侵位时代进行精确限定,利用Sr-Nd同位素示踪含矿岩体的岩浆源区,不仅为浙江斑岩型矿床成因的深入研究增加了新资料,还对浙西下一步找矿勘探具有重要意义。浙江常山里山岭斑岩型铜矿床位于钦杭成矿带东段,受球川-萧山深断裂带控制。该矿床铜矿化主要赋存于花岗斑岩体中。含矿花岗斑岩为高硅、富碱、高分异、过铝质S型花岗岩。岩体的稀土分布型式右倾,整体呈“海鸥型”,有明显负Eu异常。岩石亏损Sr、Ba等大离子亲石元素,富集Nb、Ta、Zr、Hf、Ti、Y、Yb等高场强元素。含矿花岗斑岩锆石SHRIMP U-Pb年龄为(131±2)Ma,为早白垩世构造-岩浆活动的产物,形成于中国东部岩石圈减薄背景。岩浆岩(87Sr/86Sr)i值为0.679 95~0.721 08,平均0.701 14。εNd(t)值为-8.4~-5.8,平均-6.7。Sr-Nd同位素特征表明含矿花岗斑岩源区主要为地壳,兼有少量地幔物质的混染。 相似文献
532.
张广才岭是中生代花岗质岩浆作用较为发育的地区,但关于该地区花岗岩的形成时代,缺少精确的同位素年龄资料.本文通过“黑龙江1:5万大贯屯(L52E023007)等四幅区域地质矿产调查”项目,对工作区内的花岗质岩进行了锆石U-Pb同位素测年,结果显示:三叠纪花岗岩形成于224~229 Ma,侏罗纪侵入岩形成于202~193 Ma. 相似文献
533.
越南西北部Posen花岗岩锆石U-Pb年龄和Hf同位素组成特征 总被引:2,自引:2,他引:0
HIEU PhamTrung 陈福坤 祝禧艳 王伟 NGUYEN ThiBichThuy BUI MinhTam NGUYEN QuangLuat 《岩石学报》2009,25(12):3141-3152
本文报道出露于越南西北部的Posen花岗岩岩体锆石U-Pb年龄和Hf同位素组成特征,讨论岩石成因和该地区新元古代岩浆作用的大地构造意义.分析3个花岗岩样品获得723Ma至760Ma的锆石U-Pb年龄,表明花岗岩形成于新元古代.该花岗岩的锆石Hf同位素组成有较大的变化范围,ε_(Hf)(t)值变化范围为-16.1至+3.4,单阶段Hf模式年龄为1186~1945Ma,暗示Posen花岗岩有着复杂的源区物源组成.在误差范围内,锆石两阶段Hf同位素模式年龄值主要集中在2.0~2.1Ga,与两阶段Nd同位素模式年龄值2.1~2.2Ga一致,说明花岗岩体主要由古元古代地壳物质部分熔融形成的.部分锆石颗粒具有正ε_(Hf)(t)值,可能指示花岗岩岩浆形成过程中存在壳-幔混合相互作用.在越南西北部发育新元古代岩浆作用可能与扬子板块广泛发育的、伴随Rodinia超大陆裂解过程的岩浆活动存在成因的联系,也揭示越南西北部地体可能与扬子板块具有亲缘关系,因此,可以推断马江断裂带应该代表印支板块和华南板块之间的古特提斯缝合带在越南西北部的延伸. 相似文献
534.
吉林东部大蒲柴河adakites锆石U-Pb年龄、Hf同位素特征及其意义 总被引:2,自引:2,他引:0
地球化学研究表明,大蒲柴河岩体具有典型的埃达克岩特征,来自加厚下地壳的部分熔融作用.本文采用激光等离子质谱对该岩体进行了U-Pb同位素定年,结果表明该岩体为晚侏罗世(165Ma)岩浆活动的产物.锆石的LA-MC-ICPMS Hf同位素研究结果显示,ε_(Hf)(165Ma)范围为-5.02~5.43,二阶段Hf模式年龄(t_(DM2))范围为965~1622Ma,暗示原始母岩浆为两种不同源区岩浆的混合.另外,Hf同位素研究表明,研究区在中-新元古代时(965~1304Ma)曾经历了一次重要的地壳增生事件. 相似文献
535.
东秦岭寨凹钼矿床辉钼矿Re-Os同位素年龄及熊耳期成矿事件 总被引:5,自引:5,他引:0
河南寨凹钼矿床位于东秦岭钼矿带,是近年来新发现的脉状钼矿床.9件辉钼矿样品Re-Os模式年龄介于1603.1±10.8~2031.9±10.2Ma,其中7件样品给出了精确的等时线年龄为1762±31Ma(1σ误差,MSWD=3.6),模式年龄的加权平均值为1753±26Ma(1σ误差,MSWD=3.2),表明寨凹钼矿形成于古元古代或熊耳期,代表着~1.76Ga左右的钼成矿事件.根据区域地质演化,认为寨凹钼矿形成于与熊耳群弧火山岩建造相当的活动大陆边缘岩浆弧背景.寨凹矿床的发现表明,熊耳期成矿事件虽遭受后期多次增生和碰撞造山作用的改造和破坏,但仍可在秦岭造山带最北部保留. 相似文献
536.
537.
q关于藏北羌塘中北部地区的变质地层的划分及其时代归属一直有不同的认识。红脊山地区出露的猫耳山岩组是一套由变质碎屑岩夹变质基性火山岩、大理岩和少量硅质岩组成,遭受了低角闪岩相变质作用改造的地层体,泥质变质岩中出现了十字石、蓝晶石、石榴石、角闪石等变质矿物,是羌塘中北部地区出露面积较大,变形强变质较深的构造岩石地层单位。其岩性组合、变质特征以及形成的构造环境均与上石炭统擦蒙组、展金组有明显的区别,二者之间为断层接触关系。根据岩性组合特征及岩石地球化学特征研究表明,猫耳山岩组是弧后盆地沉积的产物。获得角闪片岩全岩Sm—Nd等时线年龄值401±18Ma,可能代表了猫耳山岩组的沉积时代,也是红脊山地区早泥盆世或更早的地质时期发生了一次弧后盆地扩张作用与沉积演化的年代学记录。 相似文献
538.
The influence of volcanism on paleoclimate in the northeast of China: Insights from Jinchuan peat, Jilin Province, China 总被引:3,自引:0,他引:3
Just like contemporary sediments, peat itself is a good repository of information about climate change, the effects of volcanic
activity on climate change have been truly recorded in peat, since it is a major archive of volcanic eruption incidents. A
section of sand was identified as tephra from the Jinchuan peat, Jilin Province, China, for the grains look like slag with
surface bubbles and pits, characterized by high porosity, and loose structure with irregular edges and corners. According
to the peat characteristics of uniform deposition, the tephra was dated at 2002–1976 a B.P. by way of linear interpolation,
so the time of volcanic eruption was 15 B.C.–26 A.D. (the calibrated age). While the geochemical characteristics of tephra
in this study are quite the same as those of tephra from the Jinlongdingzi volcano at Longgang and from alkaline basaltic
magma, with the contents of SiO2<55%, and the similar contents to Al2O3 and Fe, but the contents of Na2O>K2O. We speculated that the tephra in this study came from the Longgang volcano group. Compared with 11 recorded volcanic eruption
events as shown on the carbon and oxygen isotope curves of the Jinchuan peat cellulose, it is obviously seen that adjacent
or large-scale volcanic eruptions are precisely corresponding to the minimum temperature and humidity. It seems that these
volcanic eruptions indeed affected the local climate, leading to the drop of regional temperature and humidity. As a result,
there was prevailing a cold and dry climate there, and all these changes can be well recorded in peat. So the comparison of
volcanic eruption events with information about climate change developed from peat, can provide strong evidence for the impact
of volcanism on climate change. 相似文献
539.
SHI Yuruo ZHAO Xitao MA Yinsheng HU Daogong LIU Qisheng WU Zhenhan ZHAO Yuanyi LIU Dunyi 《《地质学报》英文版》2009,83(2):310-320
The Yunmengshan Geopark in northern Beijing is located within the Yanshan range. It contains the Yunmengshan batholith, which is dominated by two plutons: the Yunmengshan gneissic granite and the Shicheng gneissic diorite. Four samples of the Yunmengshan gneissic granite give SHRIMP zircon U–Pb ages from 145 to 141 Ma, whereas four samples of the Shicheng gneissic diorite have ages from 159 Ma to 151 Ma. Dikes that cut the Yunmengshan diorite record SHRIMP zircon U–Pb age of 162±2 and 156±4 Ma. The cumulative plots of zircons from the diorites show a peak age of 155 Ma, without inherited zircon cores, and the peak age of 142 Ma for granite is interpreted as the emplacement age of the Yunmengshan granitic pluton, whose igneous zircons contain inherited zircon cores. The data presented here show that there were two pulses of magmatism: early diorites, followed c13 Ma later by true granites, which incorporated material from an older continental crust. 相似文献
540.
《The Professional geographer》2013,65(3):483-493
The age patterns of U.S. internal migration, while examined extensively at the national level, have not been fully explored at the regional scale. This study examines, using 1985 - 1990 census data, the state-level variations in two aspects of lifecycle mobility: the mobility level, or the average number of moves made over the lifecycle, and the mobility timing, or the age at which half the lifetime moves are completed. It further delineates typologies of states based upon their age structure of mobility. The study found that regional patterns in the mobility level showed some evidence of the Snowbelt-Sunbelt patterns that characterized economic restructuring in the 1980s. Geographic patterns of mobility timing were less clear; however states in the West and the South showed somewhat more young distributions than the other regions. Further, there was a statistically significant relationship between mobility levels and timing: states with higher mobility levels also exhibited older mobility profiles, as a consequence of disproportionately high elderly mobility rates. The study highlights the regional differences in mobility behavior, and the interplay between the “how much” and the “when” of mobility. 相似文献