| 苏鲁造山带威海古元古代泥质麻粒岩锆石U-Pb年龄和Hf同位素特征及其构造属性 |
| |
| 引用本文： | 熊志武,续海金,王攀,章军锋,刘强. 苏鲁造山带威海古元古代泥质麻粒岩锆石U-Pb年龄和Hf同位素特征及其构造属性[J]. 地球科学, 2021, 46(2): 504-526. DOI: 10.3799/dqkx.2020.036 |
| |
| 作者姓名： | 熊志武 续海金 王攀 章军锋 刘强 |
| |
| 作者单位： | 中国地质大学地球科学学院, 湖北武汉 430074 |
| |
| 摘 要： | 威海地区出露古元古代泥质麻粒岩,其构造属性仍存在争议.泥质麻粒岩以透镜体的形式出露在花岗质片麻岩中,透镜体从核部到边部的岩性逐渐变化:未变形的粗粒泥质麻粒岩、面理化的细粒泥质麻粒岩、石榴黑云片麻岩和混合岩化麻粒岩.粗粒泥质麻粒岩,粗粒斑状变晶结构,块状构造;细粒泥质麻粒岩,细粒斑状变晶结构,面理发育;石榴黑云片麻岩,斑...
|
| 关 键 词： | 泥质麻粒岩 古元古代 锆石 构造属性 苏鲁造山带 地球化学 地质年代学 |
| 收稿时间： | 2019-12-19 |
Zircon U-Pb Age and Hf Isotope of Paleoproterozoic Pelitic Granulites at Weihai,Sulu Orogen:Implications for Tectonic Affinity |
| |
| Xiong Zhiwu,Xu Haijin,Wang Pan,Zhang Junfeng,Liu Qiang. Zircon U-Pb Age and Hf Isotope of Paleoproterozoic Pelitic Granulites at Weihai,Sulu Orogen:Implications for Tectonic Affinity[J]. Earth Science-Journal of China University of Geosciences, 2021, 46(2): 504-526. DOI: 10.3799/dqkx.2020.036 |
| |
| Authors: | Xiong Zhiwu Xu Haijin Wang Pan Zhang Junfeng Liu Qiang |
| |
| Affiliation: | (School of Earth Sciences,China University of Geosciences,Wuhan 430074,China) |
| |
| Abstract: | Paleoproterozoic pelitic granulites have been reported in Weihai region,the tectonic affinity of which is still under controversy.The pelitic granulite occur as a lens in the granitic gneisses and the lithologies of the lens gradually changes from the core to the margin,from undeformed coarse-grained granulite,foliated fine-grained granulite,garnet-biotite-gneiss to migmatized granulite.The coarse-grained pelitic granulite exhibits coarse-grained porphyroblastic texture.The fine-grained pelitic granulite shows a weakly foliated layer with a fine-grained porphyroblastic texture.The garnet-biotite-gneiss displays porphyroblastic texture.The three samples described above mainly comprise of garnet+biotite+plagioclase(antiperthite)+quartz+sillimanite.The migmatite is made up of melanosomes and leucosomes,in which the former mainly consists of garnet+plagioclase+biotite+quartz+sillimanite and the latter has mineral assemblage of quartz+plagioclase+K-feldpsar.All of the four samples contain the accessory mineral assemblage of rutile+zircon+monazite.Zircons from the coarse-grained pelitic granulite are round or elliptical in shape and show homogenous cloudy zoning or patchy zoning in internal structure,and they have low Th/U ratios(0.01-0.30,mostly<0.1),flat HREE patterns with positive Ce and negative Eu anomalies and high Hf/Y ratios(19-537,mostly>100).These characteristics are consistent with the granulite-facies zircon growth.Ti-in-zircon thermometers give temperature of 788-892℃(mean=837±24℃).These metamorphic zircons yield an upper intercept age of 1863±18 Ma and a concordant 206Pb/238U age of 1832±23 Ma,εHf(t)values ranging from-3.4 to-4.9(mean=-4.23±0.35)and corresponding TDM2 are between 2716±107 Ma and 2807±93 Ma(mean=2767±44 Ma).The morphology and trace element characteristics of the zircon grains from fine-grained pelitic granulite also suggest a typical granulite-facies metamorphic zircon.The calculated metamorphic temperature is 804-909℃(mean=845±23℃).Metamorphic zircons define an upper intercept age of1823±14 Ma with a tight cluster concordant206Pb/238U age of 1812±13 Ma.TheεHf(t)values of them range from-3.7 to-5.7(mean=-4.67±0.37).Calculated TDM2 are from 2705±133 Ma to 2826±116 Ma(mean=2766±46 Ma).Zircon grains from the garnet-biotite-gneiss also grew under granulite-facies condition according to the CL and trace element features.The metamorphic temperature calculated based on the Ti contents in zircon is from 785℃to 923℃(mean=820±32℃).U-Pb dating of zircons gives a discordant upper intercept age of 1807±22 Ma.TheεHf(t)values range from-4.5 to-9.0(mean=-6.07±0.48).TDM2 range from 2742±90 Ma to 3020±92 Ma(mean=2839±41 Ma).Most of the zircons from the migmatite exhibit a core-rim texture comprising of granulite-facies metamorphic core and a narrow anatectic rim.The metamorphic cores give temperature ranging from 754℃to 875℃(mean=818±30℃)and yield an upper intercept age of 1822±19 Ma.TheεHf(t)values are of-4.3 to-6.3(mean=-5.47±0.35)and corresponding TDM2 are between 2742±82 Ma and 2864±91 Ma(mean=2814±43 Ma).In conclusion,the pelitic granulite,garnet-biotite-gneiss and migmatite have experienced the same granulite-facies metamorphism at about~1.8 Ga and they share a common protolith which was derived from Neoarchean(2.7-2.8 Ga)crust.The changed lithologies from core to the margin of the pelitic granulite lens may be caused by the collisional orogeny during the late Triassic.Thus,the pelitic granulites in Weihai region have the tectonic affinity to NCC and formed when involved in the evolution of supercontinent Columbia,then they incorporated into the Sulu ultrahigh-pressure metamorphic belt during the collision between the Yangtze and the North China cratons and subsequently exhumed in Triassic. |
| |
| Keywords: | pelitic granulite Paleoproterozoic zircon tectonic affinity Sulu orogen geochemistry geochronology |
| 本文献已被 CNKI 维普 万方数据 等数据库收录！ |
| 点击此处可从《地球科学》浏览原始摘要信息 |
|
点击此处可从《地球科学》下载免费的PDF全文 |
|
