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991.
同属中央造山系的西秦岭和东昆仑两造山带之间的衔接转换关系,长期以来一直是有关中国中央造山系研究中的一个争论的焦点。本文在前人对发育于两造山带衔接区的布青山、阿尼玛卿以及苦海—赛什塘3条蛇绿构造混杂带大量研究的基础上,通过进一步的调查以及同位素年代学研究发现,这3条蛇绿构造混杂带并非相互独立存在,它们在物质组成、结构构造、几何形态、同位素年代学特征上构成较为典型的三向联结构造,即秦—昆三向联结构造。该构造系统基本经历了自泥盆纪的GGG型经石炭纪一二叠纪的RRA型到二叠纪晚期的SSS型三向联结构造类型的时空转化过程.最终在晚三叠世时期结束并使西秦岭与东昆仑完成了有机的衔接。 相似文献
992.
辽宁凌源柏杖子金矿区花岗岩SHRIMP锆石U-Pb年龄 总被引:6,自引:0,他引:6
采用SHRIMP测年方法测得柏杖子金矿区含矿花岗岩的锆石U-Pb年龄为(222±3)Ma,与区内都山花岗岩基和三家子金矿区花岗斑岩的年龄一致,属中生代印支期后碰撞花岗岩。该年龄限定了金矿化年龄的下限,即金矿化不可能早于印支期,但并不能确定金矿化的精确年龄。根据金矿脉与后期岩脉伴生的特征,矿化可能发生在中生代燕山期。 相似文献
993.
山东省日照市官山闪长玢岩锆石SHRIMP年龄:印支期岩浆热事件及其对超高压变质岩折返历史的限定 总被引:4,自引:0,他引:4
对苏鲁超高压变质带日照官山地区侵入于榴辉岩中的原生块状闪长玢岩进行了锆石SHRIMP年龄分析。结果显示,数据点构成的不一致线与一致线上交点年龄为(876±62)Ma,下交点年龄为(201±20)Ma。上交点年龄为残余锆石年龄,下交点年龄大致代表了闪长玢岩的形成时代。苏鲁超高压变质带中存在较广泛的印支期岩浆热事件。假定超高压变质作用发生于228Ma,推算出闪长玢岩侵位前超高压变质岩的折返速率大致为3.63mm/a,闪长玢岩侵位后超高压变质岩的折返(剥蚀)速率大致为0.03mm/a。 相似文献
994.
995.
DI Yongjun WU Ganguo ZHANG Da SONG Biao ZANG Wenshuan ZHANG Zhongyi LI Jinwen 《《地质学报》英文版》2005,79(6):795-802
Abstract This paper determines the crystallization ages of the Xiaotongguanshan quartz monzodiorite and Shatanjiao quartz monzonite porphyry from the Tongling area using the SHRIMP zircon U‐Pb method. The crystallization age of the former is 142.8±1.8 Ma; that of the latter is 151.8±2.6 Ma. These data indicate that they were formed during the Late Jurassic (142.8 to 151.8 Ma). Zoned magma chamber was formed because of double diffusive convection. Therefore, the intrusive sequence of magma is generally from quartz monzonite through quartz monzodiorite to pyroxene monzodiorite, i.e. an inverted sequence. 相似文献
996.
New Chronological Evidence for Indosinian Diagenetic Mineralization in Eastern Xinjiang, NW China 总被引:7,自引:2,他引:7
LI Huaqin CHEN Fuwen LU Yuanf YANG Hongmei GUO Jing MEI Yuping Yichang Institute of Geology Mineral Resources Gangyao Ro Yichang Hubei 《《地质学报》英文版》2005,79(2):264-275
1 IntroductionMineralization in E. Xinjiang constitutes an importantpart of the Mid-Asian Metallogenetic Province. A greatdeal of nonferrous, ferrous, rare and noble metaldeposits of different genetic types and ages were formedduring different crustal evolution stages and werecontrolled by regional tectonic evolution. Large-scalemineralization of metallic deposits and relatedmagmatism mainly occurred during the Carboniferous toPermian periods (Li et al., 1998; Ji et al., 1999; Mao etal., 2… 相似文献
997.
SHRIMP U–Pb zircon studies on two post-collisional granitic plutons and reassessment of the data previously reported for two anatectic gneissic granites are used to assess the late Neoproterozoic history of the Florianópolis Batholith, southern Brazil. The results, supported by SEM backscattered and cathodoluminescence imagery, identify inherited zircon populations and confirm the long-lived, crustal recycling processes responsible for the accretion of the batholith. The study casts new lights on the timing of the processes involved in the generation and modification of the internal structure of distinct zircon populations, and enables discrimination to be made between inherited cores and melt-precipitated overgrowths. New dating of two post-tectonic plutons (samples 1 and 2) revealed crystals showing magmatic-textured cores sharply bounded by melt-precipitated overgrowths. The U/Pb isotopic results from both samples spread along concordia by ca. 40 m.y. (sample 1) to 100 m.y. (sample 2), clustering in two closely spaced (bimodal), partially overlapping peaks. Melt-precipitated rims and homogeneous new grains, dated at ca. 600 Ma, furnish the crystallisation age of the plutons. The magmatic textured cores and xenocrysts dated at ca. 630–620 Ma are interpreted as inherited restitic material from supposedly short-lived (meta)granitic sources. The reassessment of previous SHRIMP data of two banded anatectic granitoids (samples 3 and 4) revealed more complex morphological patterns, in which the overgrown inherited cores are sharply bounded against large melt-precipitated rims, dated at ca. 600 Ma and 592±2 Ma, respectively. Major populations of magmatic-textured inherited cores dated at 2006±3 Ma and 2175±13 Ma characterise samples 3 and 4, respectively. The latter additionally shows metamorphic and magmatic inherited cores with a large range of ages (ca. 2900–620 Ma), suggesting partial melting of metasedimentary components. The main magmatic Paleoproterozoic core populations are interpreted as inherited restite from partial melting of the adjacent (meta)tonalitic gneiss and amphibolitic country-rock (paleosome). The recognition of the (melt-precipitated) Neoproterozoic overgrowths and new crystals, and the restite provenance of the cores, supplants a previous interpretation of Paleoproterozoic magmatism (cores) and Neoproterozoic (solid-state) metamorphic overprint. As a major consequence of the former interpretation, the unit was mistakenly considered part of major Paleoproterozoic gneissic remnant within the Neoproterozoic Florianópolis Batholith/arc. 相似文献
998.
The Schurwedraai alkali granite is one of a number of prominent ultramafic-mafic and felsic intrusions in the Neoarchaean to Palaeoproterozoic sub-vertical supracrustal collar rocks of the Vredefort Dome, South Africa. The alkali granite intruded the Neoarchaean Witwatersrand Supergroup and has a peralkaline to peraluminous composition. A new zircon SHRIMP crystallization age of 2052 ± 14 Ma for the Schurwedraai alkali granite places it statistically before the Vredefort impact event at 2023 ± 4 Ma and within the accepted emplacement interval of 2050–2060 Ma of the Bushveld magmatic event. The presence of the alkali granite and associated small ultramafic-mafic intrusions in the Vredefort collar rocks extends the southern extremity of Bushveld-related intrusions to some 120 km south of Johannesburg and about 150 km south of the current outcrop area of the Bushveld Complex. The combined effect of these ultramafic-mafic and felsic bodies may have contributed to a pronouncedly steep pre-impact geothermal gradient in the Vredefort area, and to the amphibolite-grade metamorphism observed in the supracrustal collar rocks of the Vredefort Dome. 相似文献
999.
Zircon SHRIMP Dating for the Weiya Pluton, Eastern Tianshan: Its Geological Implications 总被引:18,自引:4,他引:18
ZHANG Zunzhong GU Lianxing WU Changzhi LI Weiqiang XI Aihua WANG Shuo State Key Laboratory of Mineral Deposit Research 《《地质学报》英文版》2005,79(4):481-490
1 Introduction Voluminous literature has resulted from study of the geology and tectonic evironments of post-orogenic granitoids in eastern Tianshan (He et al., 1995; Han et al., 1997; Gu et al., 1999, 2001; Li et al., 2003; Chen et al., 2004). Previous contributions (Hu et al., 1997; Li et al., 2003) indicate that major events of continental collision in northern Xinjiang occurred around 300 Ma. Then, the tectonics converted from compression to extension, resulting in the uplifting of th… 相似文献
1000.
NIU Baogui HE Zhengjun SONG Biao REN Jishun XIAO Liwei Institute of Geology Chinese Academy of Geological Sciences Beijing Beijing SHRIMP Centre Beijing 《《地质学报》英文版》2004,78(6)
A zircon U-Pb geochronological study on the volcanic rocks reveals that both of the Zhangjiakou and Yixian Formations, northern Hebei Province, are of the Early Cretaceous, with ages of 135-130 Ma and 129-120 Ma, respectively. It is pointed out that the ages of sedimentary basins and volcanism in the northern Hebei -western Liaoning area become younger from west to east, i. e. the volcanism of the Luanping Basin commenced at c. 135 Ma, the Luotuo Mount area of the Chengde Basin c. 130 Ma, and western Liaoning c. 128 Ma. With a correlation of geochronological stratigraphy and biostratigraphy, we deduce that the Xing'anling Group, which comprises the Great Hinggan Mountains volcanic rock belt in eastern China, is predominantly of the early-middle Early Cretaceous, while the Jiande and Shimaoshan Groups and their equivalents, which form the volcanic rock belt in the southeastern coast area of China, are of the mid-late Early Cretaceous, and both the Jehol and Jiande Biotas are of the Early Cretaceous, not L 相似文献