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61.
古特提斯缝合带澜沧江段花岗岩高温高压实验模拟 总被引:3,自引:0,他引:3
对古特提斯主体遗迹的云南西部昌宁-孟连构造混杂缝合带、临沧花岗岩基、澜沧江韧性变形变质带进行了岩石高温高压三轴变形实验模拟研究.以期对该构造带形成时期所处的构造物理环境作出判断。实验岩洋取自紧邻澜沧江韧性剪切变形变质带西侧的临沧花岗岩基。实验后样品产生了一系列新生显微构造,对应的地壳深度环境相当于中下地壳(13-18km)。澜沧江韧性变形变质带花岗岩的显微组构以动力重结晶颗粒极为发育为特征,表明其形成时的环境远比实验深度更深。综合考虑临沧花岗岩基现在的厚度(达15km)和花岗岩浆流动的上限深度(8-10km)以及风化剥蚀量.可以认为临沧花岗岩基的形成深度可大于25km,原始岩浆源于下地壳下部.接近莫霍面的顶面。澜沧江韧性变形变质带的形成与临沧岩基向东逆冲相关.它直抵古特提斯俯冲板块下插滑动顶面。研究表明,昌宁-孟连古特提斯曾发生过真正意义上的大规模洋壳俯冲.是一个具有较大规模的古洋盆。 相似文献
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滇西无量山岩群为原1:100万下关幅(1975)命名,为一套浅变质砂岩和泥岩,形成于滨海相-浅海陆棚相,其时代一般认为属古生代,但一直缺乏化石依据或准确的年龄数据.本次1:5万区调在澜沧江西岸云龙县毛草坪村无量山岩群四段(PzW4)的下部和上部获得两层变质基性火山岩夹层,根据野外岩石产状、镜下薄片鉴定、岩石地球化学综合分析恢复其原岩为玄武岩,形成于大洋扩张环境.采用LA-ICP-MS技术,对下部和上部变质基性火山岩中的锆石进行了U-Pb同位素测定,分别获得206Pb/238U年龄为(327±11)Ma(N=14,MSWD=6.7)和(284±3.7)Ma(N=27,MSWD=4.9),为早石炭世晚期和早二叠世晚期,这为无量山岩群形成时代及其演化提供了重要的年龄依据,对于进一步深入研究古特提斯洋晚古生代的构造属性与演化历史具有重要意义. 相似文献
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SHRIMP ziron U-Pb geochronology of early Mesozoic felsic igneous rocks from the southern Lancangjiang and its tectonic implications 总被引:5,自引:0,他引:5
Peng Touping Wang Yuejun Fan Weiming Liu Dunyi Shi Yuruo Miao Laicheng 《中国科学D辑(英文版)》2006,49(10):1032-1042
The SHRIMP zircon U-Pb geochronology of three typical samples, including two monzonitic granites from the Lincang batholith
and a rhyolite from the Manghuai Formation are presented in the southern Lancangjiang, western Yunnan Province. The analyses
of zircons for the biotite monzonitic granites from the northern (02DX-137) and southern (20JH-10) Lincang batholith show
the single and tight clusters on the concordia, and yield the weighted mean 206Pb/238U ages of 229.4 ± 3.0 Ma and 230.4 ± 3.6 Ma, respectively, representing the crystallized ages of these granites. The zircons
for the rhyolitic sample (02DX-95) from the Manghuai Formation give a weighted mean 206Pb/238U age of 231.0 ± 5.0 Ma. These data suggest that the igneous rocks from the Lincang granitic batholith and Manghuai Formation
have a similar crystallized age. In combination with other data, it is inferred that both were generated at a narrow age span
(∼230 Ma) and were originated from the postcollisional tectonic regime. An early Proterozoic 206Pb/238U apparent age of 1977±44 Ma is additionally obtained from one zircon from the biotite monzonitic granite (southern Lincang
batholith), indicative of development of the early Proterozoic Yangtze basement in the region. These precisely geochronological
data provide important constraints on better understanding the Paleozoic tectonic evolution of the Tethys, western Yunnan
Province. 相似文献
69.
2005年雨季"三江源"地区对流云的特征分析 总被引:1,自引:1,他引:1
利用2005年6~9月逐日逐时FY-2C气象卫星数值云图资料,计算和分析了青藏高原三江源区域的对流云和中尺度对流系统(s-MCS)的发生频率。结果表明,该区域主要以对流云为主,对流云占总云量的80%以上,利用TBB值得出该区域对流云发生源地主要集中在两大区域,其中以32°~35°N,93°~98°E为主要多发区(称为第一高发区),以35°~37°N,91°~95°E为次多发区(称为第二高发区);该区域对流云存在着明显的日变化,22:00(世界时,下同)~06:00(上半夜)对流云旺盛,06:00~14:00(下半夜)及清晨对流云很少。最后结合地面观测资料给出了云顶亮温与地面降水的关系。 相似文献
70.
SHRIMP zircon U-Pb geochronology of early Mesozoic felsic igneous rocks from the southern Lancangjiang and its tectonic implications 总被引:6,自引:0,他引:6
The SHRIMP zircon U-Pb geochronology of three typical samples, including two monzo nitic granites from the Lincang batholith and a rhyolite from the Manghuai Formation are presented in the southern Lancangjiang, western Yunnan Province. The analyses of zircons for the biotite monzonitic granites from the northern (02DX-137) and southern (20JH-10) Lincang batholith show the single and tight clusters on the concordia, and yield the weighted mean 206Pb/238U ages of 229.4 ± 3.0 Ma and 230.4 ± 3.6 Ma, respectively, representing the crystallized ages of these granites. The zircons for the rhyolitic sample (02DX-95) from the Manghuai Formation give a weighted mean 206Pb/238U age of 231.0 ± 5.0 Ma. These data suggest that the igneous rocks from the Lincang granitic batholith and Manghuai Formation have a similar crystallized age. In combination with other data, it is inferred that both were generated at a narrow age span (~230 Ma) and were originated from the postcollisional tectonic regime. An early Proterozoic 206Pb/238U apparent age of 1977±44 Ma is additionally obtained from one zircon from the biotite monzonitic granite (southern Lincang batholith), indicative of devel- opment of the early Proterozoic Yangtze basement in the region. These precisely geochronological data provide important constraints on better understanding the Paleozoic tectonic evolution of the Tethys, western Yunnan Province. 相似文献