大兴安岭中部塔尔气中侏罗世碰撞后花岗质岩石的确定及地质意义     

于泓超  和钟铧  隋振民  董玉  朱凯 《岩石学报》2020,36(12):3721-3740

大兴安岭地区以发育巨量显生宙花岗岩为特征，而且通过对这些花岗质岩浆作用的期次、特征以及成因进行研究对于探讨中国东北地区构造-岩浆演化历史具有重要意义。本文通过对大兴安岭中部塔尔气杂岩体进行锆石U-Pb年代学、全岩主量元素和微量元素以及锆石Hf同位素组成分析，确定这些花岗质岩石的形成时代、成因以及构造背景。塔尔气杂岩体是早石炭世、中侏罗世和早白垩世三期岩浆作用的产物，且中侏罗世花岗质岩石是塔尔气杂岩体的主体，其主要岩石类型为花岗闪长岩、二长花岗岩和正长花岗岩。这些花岗质岩石的锆石均呈自形-半自形，具有典型的震荡生长环带和高Th/U（0.35~2.02）比值，表明其为岩浆成因锆石。LA-ICP-MS锆石U-Pb年龄结果显示中侏罗世花岗质岩石主要形成于173~166Ma。它们的SiO₂含量为70.54%~77.96%，Na₂O/K₂O比值为0.86~1.28，Al₂O₃含量为11.67%~14.83%，TiO₂含量为0.07%~0.60%，具有较低的MgO含量（0.02%~0.74%），A/CNK值介于0.9~1.1，表明这些花岗质岩石属于高钾钙碱性I型花岗岩，具有准铝质-弱过铝质特征。塔尔气中侏罗世花岗质岩石富集Rb、Th、U、Zr和轻稀土元素，亏损Ba、Nb、Ta、Sr、Ti和重稀土元素，且具有中等到强烈的铕负异常。此外，它们的锆石¹⁷⁶Hf/¹⁷⁷Hf值为0.282874~0.282985，ε_Hf（t）值为+7.01~+10.9，二阶段模式年龄为768~516Ma。上述地球化学特征暗示其原始岩浆源于新元古代-显生宙期间新增生陆壳物质的部分熔融，源区残留相主要为斜长石和角闪石，并在岩浆演化过程中经历了斜长石和钾长石等矿物的分离结晶作用。结合前人研究成果，认为研究区中侏罗世花岗质岩石形成于碰撞后伸展环境，可能与蒙古-鄂霍茨克洋闭合后的岩石圈拆沉作用有关。  相似文献   

U–Pb geochronology and Raman spectroscopy of zircons from the granites in the Xihuashan and Tieshanlong Deposit: Implications for W‐Sn mineralization in Southern Jiangxi Province,South China     

Xiao‐fei Guo  Kai‐xing Wu  Yu Tian  Xiao‐bing Zhang 《Resource Geology》2020,70(2):141-156

The Xihuashan and Tieshanlong tungsten deposit is an important large quartz vein‐type W‐polymetallic deposit in the southern Jiangxi Province, eastern Nanling Range. Zircon U–Pb analyses of representative ore‐forming granites from the Xihuashan and Tieshanlong tungsten deposit yield ages of 146.3 ± 2.9 Ma and 146.0 ± 3.8 Ma, respectively. According to the zircon Raman spectroscopy, these granitic rocks are disturbed by different degrees of hydrothermal alteration, whereas most zircons exhibit primary oscillatory zoning and Th/U ratios in the range of magmatic zircon, which means the analysis results represent the crystallization age of metallogenetic granitic assemblages. In combination with regional geological data, it is suggested that the Late Jurassic is probably another important episode of granitic magmatism and W‐Sn mineralization in southern Jiangxi Provinces, even South China.  相似文献   

大兴安岭南段阿鲁科尔沁旗地区林西组沉积环境特征及其时限的地质意义     

董清水  何春生  楼仁兴  任锡钢  张超  张渝金  许圣传 《吉林大学学报(地球科学版)》2020,50(2):425-441

针对兴蒙—松嫩地区林西组沉积环境、沉积时限及古亚洲洋最终闭合时间等争议问题，通过对阿鲁科尔沁旗罕庙地区林西组的岩性、古生物、微量元素及碎屑锆石U-Pb测年等综合研究认为：林西组发育淡水双壳类和叶肢介化石，微量元素Sr/Ba值主要分布在0.05~0.18之间（平均值为0.12），B/Ga值主要分布在1.84~3.22之间（平均值为2.50），V/Cr值介于1.36~2.21之间（平均值为1.81），其沉积时期应为缺氧或贫氧的淡水湖泊环境。结合林西组砂岩碎屑锆石具有多时代物源特征、最年轻年龄为251 Ma、沉积下限年龄为晚二叠世等特征推测，古亚洲洋在研究区的最终闭合时限应为中二叠世末期，晚二叠世时期研究区即已转化为陆相沉积。  相似文献   

2010智利Maule特大地震的同震效应   总被引：4，自引：0，他引：4       下载免费PDF全文

黄禄渊  张贝  瞿武林  张怀  石耀霖 《地球物理学报》2017,60(3):972-984

2010年智利Maule大地震是人类有观测记录以来第六大地震,基于高性能并行有限元方法,建立含地表地形和Moho面起伏的大规模非均匀椭球地球模型,计算了该地震同震效应,并根据库仑应力变化分析周围断层地震活动性和主震对余震的触发关系.结果表明:对于2010年Maule地震,地球曲率和层状结构对同震水平位移影响不可忽略,如果不采用球面分层模型,在低纬度远场可能会造成位移和应变量值均被低估,在高纬度远场可能会造成位移被夸大而应变被低估.如果不考虑介质横向不均匀和地形,同震应力降被显著低估,近场同震东西向应力变化误差最高95.4%,南北向应力变化误差最高90.8%.Illapel地区库仑应力变化约10 kPa,相当于15年构造积累,Maule地震加速了2015年Illapel地震发生.以最优破裂方向投影得到库仑应力变化,经统计70.9%余震落在库仑应力变化量值大于10 kPa区域.本次特大地震触发了Pichilemu附近M_w6.9和M_w7.0两次正断型余震.  相似文献   

Composition and textural variability along the 10 m isobath,Great Barrier Reef: Evidence for pervasive northward sediment transport     

A. Lambeck  K. J. Woolfe 《Australian Journal of Earth Sciences》2013,60(2):327-335

Previous workers have proposed that northward‐directed bedload transport dominates the inner shelf of the Great Barrier Reef lagoon. Results from a sediment sampling survey along the 10 m isobath between Bowen and Cape York reveal a series of northward trends of increasing sediment maturity and demonstrate pervasive north‐directed sediment transport interacting with a succession of sediment (fluvial) sources. South of the Tully River, the occurrence of limited compositional variability indicates significant mixing on the inner shelf. However, further north the data are highly variable, suggesting that sediment inputs from individual rivers may be retained relatively close to source. This may be related to a greater sediment trapping efficiency within northern embayments and/or by lower net rates of along‐shelf transport.  相似文献   

Marra Mamba Iron Formation stratigraphy in the eastern Chichester Range,Western Australia     

D. F. Lascelles 《Australian Journal of Earth Sciences》2013,60(4):799-806

The Marra Mamba Iron Formation is the basal member of the Hamersley Group in Western Australia and is host to major iron‐ore deposits in its upper Mt Newman Member. Previous studies have suggested that the Marra Mamba Iron Formation in the eastern Chichester Range was deposited in an isolated basin behind a barrier reef and was greatly reduced in thickness. New drilling covering a large part of the Chichester Range shows that only the lower part of the Nammuldi Member, the lowest unit of the Marra Mamba Iron Formation, remains over most of the range. However, 15 m of the Mt Newman Member, the complete MacLeod Member and the upper part of the Nammuldi Member were drilled in small north‐south synclines preserved near Mulga Downs homestead. This drilling shows that the Marra Mamba Iron Formation is similar in all respects to other occurrences in the Hamersley Province. There is no evidence of facies change or reduced thickness and therefore no evidence for a northern limit to the deposition of the Hamersley Group. Apart from the small synclines near Mulga Downs homestead, the Fortescue River alluvial deposits abutting the Chichester Range are underlain by the Roy Hill Shale Member of the Jeerinah Formation.  相似文献   

扬子地台与华南南盘江盆地大贵州滩三叠系沉积演化史   总被引：1，自引：0，他引：1  

Paul Enos  喻羑艺  魏家庸  李荣西 《地球科学与环境学报》2009,31(4):344-367

扬子地台是一个横跨华南地块的以浅海沉积为主的大型碳酸盐岩台地,南盘江盆地是发育在扬子地台碳酸盐岩台地背景之上的一个沉积盆地,从晚元古代到晚三叠世长期海相沉积演化历史中,扬子地台-南盘江盆地体系经历了多次重要的构造演化阶段.扬子地台从晚元古代到早三叠世末期一直保持为一个稳定的碳酸盐岩台地,在中三叠世末期扬子地块整体抬升,海平面下降,形成了遍及扬子主体的拉丁期大海退,从而使扬子地块大部分地区抬升为陆.南盘江盆地位于华南地块南缘,从晚元古代到晚三叠世沉积了一套厚度巨大的海相碳酸盐岩,晚三叠世发育了一套硅质碎屑的浊流沉积,区域沉积也由此转化为河流相沉积.二叠纪和三叠纪碳酸盐岩地层记录了碳酸盐岩台地长期演化历史及其特征多样的沉积建造和沉积环境,而硅质碎屑流和构造沉降速率的变化反映了盆地在三叠纪期间经历的聚合构造和前陆盆地发展过程.在三叠纪时期扬子地台沿西南-北东方向从云南围绕南盘江盆地向贵州延伸,在南盘江盆地中发育了几个孤立的碳酸盐岩台地,包括位于贵州南部和广西境内的大贵州滩和崇左-平果台地.南盘江盆地在晚二叠世发生过一次区域性的海侵事件,早三叠世时期扬子地台和几个孤立台地为由鲕粒边滩组成的低角度斜坡,中三叠世(安尼期)变为由Tubiphytes边礁组成的陡倾斜坡.盆地范围内斜坡变陡激发了Tubiphytes礁和其它的生物体发育,而且它们组成了稳定碳酸盐岩台地的边缘.位于扬子地台西部地区的关林和贞丰一带与最北部的孤立台地(大贵州滩)在安尼期发育了陡倾的边礁.在拉丁期,扬子地台在关林一带进积并与盆地碎屑沉积互层穿插沉积,而位于贞丰的台地边缘出现了由断层控制的地貌特征.与此同时,扬子地台东部(贵阳)由侵蚀滑塌边缘变为进积边缘,向盆地内部进积充填形成了超过600 m的碎屑沉积.但是,与扬子地台不同,位于最北部的孤立台地(大贵州滩)在拉丁期由加积边缘礁变为起伏明显的侵蚀陡崖和饥饿盆地边缘.晚三叠世(卡尼期)扬子地台西部下沉并被晚三叠世浊流沉积埋藏,而扬子地台东部地区在被硅质碎屑沉积埋藏之前持续沉积了一套浅水碳酸盐岩沉积.孤立台地为从南到北逐渐变陡的边缘沉积,而且发育了多个小丘,其中南部地区早期沉降后来被硅质碎屑沉积埋藏,而北部地区到后期下沉.与扬子地台西部一样,最北部的孤立台地(大贵州滩)在晚三叠世下降被碎屑沉积埋藏.以上这种差异源于华南地块南缘因构造聚合作用导致的盆地南部地区不同沉降速率.大贵州滩是盆地中演化历史最长的孤立台地,穿过大贵州滩孤立台地内部和边缘的两条正交剖面显示出了一个被断层切断的向斜构造,这样就很容易识别其沉积建造特征及演化历史.大贵州滩发育的整合的二叠系-三叠系界线剖面以及从早三叠世到中三叠世生物复苏阶段连续的巨厚沉积,使其成为一个研究二叠世末期生物大绝灭期间的海相环境以及生物生态条件最为理想的地区.  相似文献   

大九寨核心景区旅游气候资源研究   总被引：1，自引：1，他引：0  

尹建昌 《成都信息工程学院学报》2009,24(2):187-194

通过几寨沟、红原、松潘和若尔盖以及九寨沟内几个自动气象站的温、压、湿、风、太阳辐射等气象观测资料的统计计算,分析了大九寨核心旅游景区的光照、热量、水分、气压和风速等旅游气候资源.分析表明,大几寨旅游景区海拔1407～3493m,年平均气温为1.1℃～12.7℃,年平均降水量551.6～769.2mm,日照充足,干、湿季节分明,适宜旅游期可达8个月,加上丰寓的气候旅游景观,足世界上最佳的生态旅游目的地.提出了如何保持大九寨最佳生态旅游资源的可持续开发和利用是有待进一步研究的问题.  相似文献   

Palynofacies,organic geochemistry and depositional environment of the Tartan Formation (Late Paleocene), a potential source rock in the Great South Basin,New Zealand     

Poul Schiøler  Karyne Rogers  Richard Sykes  Chris J. Hollis  Brad Ilg  Dylan Meadows  Lucia Roncaglia  Chris Uruski 《Marine and Petroleum Geology》2010

Detailed palynofacies analysis of sidewall core samples taken from below, within and above the Tartan Formation (Thanetian, Late Paleocene, 58.7–55.8 Ma), a potential source rock in the epeiric Great South Basin, shows that the formation is characterised by very high percentages of degraded brown phytoclasts, rare marine algae and amorphous organic matter and thereby represents a mix of terrestrial and marine kerogen. The results indicate that the formation was deposited in a marginally marine (hyposaline), proximal environment under bottom conditions that varied from anoxic to oxic along a nearshore–offshore transect. Samples from the upper part of the underlying Wickliffe Formation indicate deposition in a marginal to normal marine, proximal environment under anoxic to oxic bottom environments. The lower part of the overlying Laing Formation was deposited in an open marine, relatively distal setting under anoxic to oxic bottom environments.  相似文献   

Late Pleistocene and Holocene glaciation of the Fish Lake valley,northeastern Alaska Range,Alaska     

Nicolás E. Young  Jason P. Briner  Darrell S. Kaufman 《第四纪科学杂志》2009,24(7):677-689

We reconstructed a chronology of glaciation spanning from the Late Pleistocene through the late Holocene for Fish Lake valley in the north‐eastern Alaska Range using ¹⁰Be surface exposure dating and lichenometry. After it attained its maximum late Wisconsin extent, the Fish Lake valley glacier began to retreat ca. 16.5 ka, and then experienced a readvance or standstill at 11.6 ± 0.3 ka. Evidence of the earliest Holocene glacial activity in the valley is a moraine immediately in front of Little Ice Age (LIA) moraines and is dated to 3.3–3.0 ka. A subsequent advance culminated at ca. AD 610–900 and several LIA moraine crests date to AD 1290, 1640, 1860 and 1910. Our results indicate that ¹⁰Be dating from high‐elevation sites can be used to help constrain late Holocene glacial histories in Alaska, even when other dating techniques are unavailable. Close agreement between ¹⁰Be and lichenometric ages reveal that ¹⁰Be ages on late Holocene moraines may be as accurate as other dating methods. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献