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采用４０Ａｒ／３９Ａｒ法和激光微区等时线方法，对南极南设得兰群岛利文斯顿岛东部产出的鲍勒斯山组火山岩重新进行了年龄测定。结果表明，４５Ｄ安山质熔岩和２６２玄武安山质熔岩的等时年龄分别为（１０５．６２±２．１１）Ｍａ和（１１１．４８±２．２３）Ｍａ，其４０Ａｒ／３９Ａｒ初始比与尼尔值相当，岩石中不含过剩氩，表明等时年龄代表岩石真正的形成年龄。脉状产出的Ａ９３５２细晶岩的４０Ａｒ／３９Ａｒ坪年龄为（９６．７±１．６）Ｍａ，计算得到等时年龄为９６．６Ｍａ，晚于熔岩喷发而形成。新的年龄数据证实了鲍勒斯山组火山岩形成于白垩纪。白垩纪火山活动曾影响了整个利文斯顿岛，在赫德半岛出露的鲍勒斯山组火山岩曾被较年轻火山岩所覆盖，构造抬升使其出露。 相似文献
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以Ｋ－Ａｒ稀释法和４０Ａｒ／３９Ａｒ阶段加热法对利文斯顿岛百尔斯半岛的熔岩和次火山岩测定了同位素年龄。新的年龄数据表明,该区火山活动在晚侏罗纪末即已开始,一直持续到晚白垩世,存在着三期火山活动的产物。侏罗纪末～早白垩世初的火山活动除有熔岩（１４６Ｍａ,１３７Ｍａ）喷出外,还发育有辉长岩侵入体（１３５Ｍａ）和辉绿岩岩墙（１２９Ｍａ）等次火山岩。安山岩（１１４Ｍａ）和石英斑岩（９４Ｍａ）则是早白垩世火山活动的结果。半岛东部具沉积夹层的玄武岩（７１Ｍａ）是区域上晚白垩世～早第三纪火山活动的代表。 相似文献
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本文采用４０Ａｒ／３９Ａｒ、Ｋ－Ａｒ和激光微区等时线方法，对乔治王岛北海岸的火山岩进行了系统的年龄测定。实验结果表明，该区的火山活动从晚白垩世延续到始新世末期，主要喷发时代为始新世。岩石的年龄由南西向北东依次变新，表明乔治王岛的火山活动中心在不断迁移，与整个南设得兰群岛火山岩的时、空分布规律相符。侵入岩比火山岩生成晚而岩石化学成分更偏酸性，说明侵入岩可能是火山岩同源岩浆分异演化的产物。这批高质量数据的获得，将为区域火山岩地层时代的厘定和构造岩浆演化过程的研究提供有力的依据。 相似文献
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东南极拉斯曼丘陵暗色麻粒岩锆石的U—Pb年龄及其地质意义 总被引：4，自引：0，他引：4
东南极拉斯曼丘陵地区代表性的原岩为镁铁质岩的暗色麻粒岩，其中猪石的Ｕ－Ｐｂ同位素年代测定表明，本区在泛非事件之间的晚元古中期可能经历过一次麻粒岩相变质作用主要由斜方辉石－单斜辉石－斜长石－石英组成的暗色麻粒岩的Ｕ－Ｐｂ不一致年龄结果为７７２．４＋７１．１／－４８．０Ｍａ。 相似文献
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西南极乔治王岛北海岩火山岩的^40Ar／39Ar和K—Ar年龄测定 总被引：1，自引：1，他引：1
本文采用＾４０Ａｒ／＾３９Ａｒ、Ｋ－Ａｒ和激光微区等时线方法，对乔治王岛北海岩的火山岩进行了系统的年龄测定。实验结果表明，该区的火山活动从晚白垩世延续到始新世末期，主要喷发时代为始新世。岩石的年龄由南西向北东依次变新，表明乔治王岛的火山活动中心在不断迁移，与整个南设得兰群岛火山岩的时、空分布规律相符。 相似文献
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《极地研究》2021,(2)
澳大利亚西缘的平贾拉造山带遭受了格林维尔期和泛非期两期高级构造热事件的影响,其构造演化过程与罗迪尼亚超大陆的聚散和冈瓦纳超大陆的拼合密切相关。本文系统总结和评述了平贾拉造山带在中元古代–早古生代期间经历的三期主要地质事件及其构造意义,并与东南极雷纳造山带的地质事件进行了对比研究。平贾拉造山带中记录的三期主要地质事件包括:(1)中元古代晚期岩浆/变质事件(1090—1020Ma),与全球格林维尔期造山作用有关,但对其详细的构造含义争议较大;(2)新元古代中期岩浆事件(780—660 Ma),具有伸展/裂谷岩浆作用特征,可能与罗迪尼亚超大陆的裂解有关;(3)新元古代晚期–早古生代(即泛非期)岩浆/变质事件(540—520 Ma),与东冈瓦纳大陆的聚合有关。地质对比研究表明,平贾拉造山带与东南极雷纳造山带所记录的中–新元古代地质事件存在明显的差别,两者不能连成一个统一的格林维尔期造山带。平贾拉造山带与普里兹湾地区的雷纳造山带部分(即普里兹造山带)都遭受到新元古代晚期–早古生代构造热事件的强烈改造,两者可能存在内在的联系。但是,普里兹湾地区新元古代中期岩浆事件的缺失表明两者可能还不能直接相连。因此,关于西澳平贾拉造山带向东南极的延伸问题尚存争议,这也是今后需要进一步研究的方向。 相似文献
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The 40 Ar 39 Ar ages of hornblendes in Grt Pl bearing amphibolite from the Larsemann Hills, East Antarctica and their geological implications 
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下载免费PDF全文 １ＩｎｔｒｏｄｕｃｔｉｏｎＡｓｐａｒｔｏｆｅｘｔｅｎｓｉｖｅｌａｔｅＰｒｏｔｅｒｏｚｏｉｃｍｏｂｉｌｅｂｅｌｔｏｆＥａｓｔＡｎｔａｒｃｔｉｃａ,ｔｈｅｕｐｐｅｒａｍｐｈｉｂｏｌｉｔｅｔｏｇｒａｎｕｌｉｔｅｆａｃｉｅｓｈｉｇｈ－ｇｒａｄｅｍｅｔａｍｏｒ... 相似文献
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~(40)Ar/~(39)Ar IsOTOPIC DATING THE BIOTITES FROM THE IGNEOUS AND METAMORPHIC ROCKS OF THE ZHONGSHAN STATION AREA 下载免费PDF全文
下载免费PDF全文 The Zhongshan Station of China is located in the Larsemann Hills, East Antarctica. Low pressure granulite facies gneisses together with late granites are outcroped in the region. Three biotite samples from a garnet segregation, a syenogranite and a granite-pegmetite were measured with ~(40)Ar/~(39)Ar incremental heating technique. Biotites from the garnet segregation give an ~(40)Ar/~(39)Ar plateau age of 504±1Ma. Biotites from the syenogranite yield an ~(40)Ar/~(39)Ar plateau age of 494±1 Ma. Biotites from the granite-pegmatite give an ~(40)Ar/~(39)Ar plateay age of 486±1Ma. They verify 500 Ma thermal event called "Pan African event" by previous K-Ar and Rb-Sr data. They are cooling ages of the biotites when the paleogeotherm of the area droped to the K-Ar closure temperature for biotite. 相似文献
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就目前认识,拉斯曼丘陵地区的所有基底和盖层岩石都卷入到了格林威尔期和泛非期高级变质和变形作用。泛非期高峰变质的时代大致在550—530 Ma,其造山晚期的花岗质岩浆作用遍及全区。我们观察到,中山站区石榴黑 云斜长片麻岩固相变质作用过程,主要是对早期锆石的重启、改造,例如,对早期岩浆锆石环带的模糊化,对锆石棱、角的溶蚀,甚至同位素体系的重启等,难以形成变质锆石（边）,退变或重启年龄平均值为522.7±6.6 Ma。峰期变质 之后侵位的花岗岩结晶年龄为545±9 Ma,意味着峰期变质应不晚于该年龄。泛非期的变形、变质作用及花岗岩可对早期“干”岩石进行某种程度的退变质改造,从而造成高级变质岩变质结构的复杂性。这种变质作用及有关的花岗岩活动似乎缘于陆块内部的活化,而不是不同陆块间的碰撞所致。 相似文献
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在1998—2017年期间,我国组织了14次东南极地质考察,将考察的范围从中山站所在的拉斯曼丘陵向外扩展了约400 km,主要包括格罗夫山、埃默里冰架东缘-西南普里兹湾、北查尔斯王子山、布朗山、赖于尔群岛和西福尔丘陵等露岩区。通过大、中比例尺的地质编图和多学科综合研究,取得如下重要进展:(1)确定格罗夫山冰下高地为泛非期(~570—500 Ma)单相变质地体,发现镁铁质和泥质高压麻粒岩并刻画了泛非期造山的精细过程,为普里兹造山带的碰撞造山成因以及冈瓦纳超大陆的多陆块汇聚模型提供了岩石学支撑;(2)论证在印度克拉通与东南极陆块之间存在一个延长2 000 km的中元古代长寿命大陆岛弧,岛弧岩浆作用从~1 500 Ma一直持续到~1 000 Ma,提出雷纳造山带格林维尔期(~1 000—900 Ma)的构造演化可能经历了从弧陆碰撞到陆陆碰撞的过程;(3)在赖于尔群岛超高温变泥质岩中识别出早期蓝晶石的残留,确定了超高温变质作用顺时针演化的精细P-T轨迹;(4)在西福尔丘陵西南部基性岩墙群中发现了格林维尔期(~960—940 Ma)不均匀麻粒岩化,变质条件达820—870℃、0.84—0.97 GPa,认为西福尔陆块也卷入到印度克拉通与东南极陆块的碰撞造山过程;(5)在西福尔丘陵东南部浅变质冰川漂砾和松散砂中获得~3.5—3.3 Ga的古老锆石U-Pb年龄,推测在西福尔丘陵东南方向存在一个从前未知的古太古代冰下陆块。建议今后在东南极面向印度洋构造域的地质考察要进一步扩展到南查尔斯王子山、内皮尔杂岩和登曼冰川,研究工作的重点仍聚焦在南极大陆如何响应地质历史时期里超级大陆的聚散过程这一关键科学问题上,并可在以下几个方面展开:(1)太古宙古老地壳及陆核的识别与全球对比;(2)格林维尔期造山记录与罗迪尼亚超大陆汇聚;(3)泛非期造山记录与冈瓦纳超大陆汇聚;(4)显生宙冈瓦纳超大陆裂解及陆块分离。通过这些考察和研究工作,可以促使我国对南极地质科学的研究达到国际先进水平。 相似文献
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Arkadiusz Derkowski Jan
rodo&#x; Magdalena Goryl Leszek Marynowski Marek Szczerba Stanis&#x;aw Mazur 《Basin Research》2021,33(1):570-593
The diagenetic history of the Ediacaran sedimentary rocks in the East European Craton (EEC) over the area extending from Arkhangelsk (Russia) in the north to Podolia (Ukraine) in the south was revealed by means of the XRD characterization and K–Ar dating of clay fractions, mudstone porosity measurements and organic geochemistry investigations. Mudstone porosity measurements produced direct evidence of shallow maximum burial of the Ediacaran sediments on the craton (Russia, Lithuania, Belarus, Volyn), not exceeding 1.5 km, and much deeper burial at the cratonic margin, in Podolia and Poland. In general, illitization of smectite and biomarker indices indicates more advanced diagenesis at the cratonic margin. K–Ar dating of authigenic illite–smectite and aluminoceladonite revealed the Palaeozoic age of mineral diagenesis (ca. 450–300 Ma) both on the craton and its margin, with older ages generally observed in the north. When the maximum palaeotemperatures were evaluated from illite–smectite and biomarkers, based on the calibrations from the conventional burial diagenetic sections, a major mismatch was detected for the cratonic area: 100°C–130°C from illite––smectite and tens of oC lower from the lipid biomarkers. This diagenetic pattern was interpreted as the result of short‐lasting (in ky scale) pulses of potassium‐bearing hot fluids migrating from the Caledonian and Variscan orogens deep in the craton interior, effectively promoting illitization in porous rocks without altering the organic matter. Analogous short pulses of fluids were responsible for numerous diagenetic phenomena, including Mississippi Valley‐Type ore deposits, in the American Midwest, in front of the Appalachians. K–Ar dating indicates that the entire Proterozoic sedimentary cover of the Great Unconformity on the EEC remained untouched by measureable post‐sedimentary changes until the early Palaeozoic, thus for over 1000 My, which is an unprecedented finding. 相似文献
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Theofilos Toulkeridis Norbert Clauer Sam Chaudhuri & Steve L. Goldstein 《Basin Research》1998,10(2):261-270
Isotopic determinations (K–Ar, Rb–Sr and Sm–Nd), and trace and rare-earth elemental analyses were made on a few biotite and clay fractions of Palaeozoic bentonite units from the eastern United States. The clay fractions were gently leached with dilute hydrochloric acid to study separately the acid-soluble minerals intimately associated with the extracted clay particles. The data highlight interesting potentials for this integrated approach to decipher complex tectonothermal evolutions of sedimentary basins. Biotite K–Ar ages are consistent with a Middle Ordovician stratigraphic age for the bentonite units with a mean age of 459±10 Ma. The clay residues give a Sm–Nd isochron age of 397±44 Ma, indicative of their crystallization during Acadian tectonothermal activity at about 200 °C. The clay leachates, which are considered to represent mineral phases different from clay material, yield a distinct Sm–Nd isochron age of 285±18 Ma which is indistinguishable from K–Ar ages obtained previously on the clays, suggesting a thermally induced diffusion of radiogenic 40Ar from clay particles during Alleghenian–Ouachita orogenic activity. The Rb–Sr system of the clay material seems to have been variably disturbed, except for the sample taken near the Allegheny Front for which an age of 179±4 Ma suggests a further localized activity of the thrust system at about 130–150 °C. Clearly the limited number of samples does not allow us to perfectly constrain an evolutionary model. However, analysis of the soluble minerals for their contents in metal and rare-earth elements suggests that metal-carrying fluids migrated during the Alleghenian–Ouachita orogenic activity in the eastern North American continent. Consequently, they could have contributed to the concentration of ore deposits in the region, but this possibility needs to be tested with a larger data base. 相似文献