来自新疆皮山县克里阳剖面磷灰石裂变径迹记录的启迪——对塔里木地块现今向西昆仑山体俯冲的疑义     

崔军文 《地质通报》2007,26(10):1245-1251

皮山县克里阳剖面是塔南坳陷带中—新生界发育最为完整、变形现象最具代表性的剖面。系统的磷灰石裂变径迹分析表明,上白垩统—中新统砂岩样品的平均径迹年龄均大于相应的地层时代,样品的P(x2)大部分小于0.1%,说明不属于同组年龄。磷灰石单颗粒径迹年龄最大值为180～190Ma,最小年龄为10～20Ma,峰值年龄为80～90Ma和50～70Ma,磷灰石的平均径迹长度为(10.82±2.01)～(9.06±2.01)μm。径迹记录表明晚白垩世至中新世时期,沉积层的主体部分并未下沉到达磷灰石的退火带深度而导致早期径迹记录的全部消失。说明新生代时期,特别是新近纪以来,尽管西昆仑造山带存在强烈的热构造作用,山前坳陷带也发生了构造沉降,但并不存在塔里木地块向西昆仑山体的大规模的陆内俯冲作用,总体看塔南坳陷带的下插深度并未超过7km(磷灰石的退火带深度)。  相似文献   

Lithofacies and eruption ages of Late Cretaceous caldera volcanoes in the Himeji–Yamasaki district, southwest Japan: Implications for ancient large-scale felsic arc volcanism     

Takahiro Yamamoto 《Island Arc》2003,12(3):294-309

Abstract The Himeji–Yamasaki region in the Inner Zone of southwest Japan is underlain mainly by Late Cretaceous volcanic rocks called the Ikuno Group or the Hiromine and Aioi Groups. A new stratigraphic and geochronological study shows that the volcanic rocks in this area consist of 15 eroded caldera volcanoes between 82 and 65 Ma; they are, in order of decreasing age, the Hiromine, Hoden, Ibo, Okawachi, Seppikosan, Hayashida, Shinokubi, Fukusaki, Kurooyama, Ise, Fukadanigawa, Nagusayama, Matobayama, Yumesaki and Mineyama Formations. These calderas vary in diameter from 1 to 20 km and are bounded by steep unconformities; they coalesce and overlap each other. The individual caldera fills are composed mainly of single voluminous pyroclastic flow deposits, which are often interleaved with debris avalanche deposits and occasionally underlie lacustrine deposits. The intracaldera pyroclastic flow deposits are made up of massive, welded or non‐welded tuff breccia to lapilli tuff, and are characterized by their great thickness. The debris avalanche deposits are ill‐sorted breccia, generated by the collapse of the caldera wall toward the caldera floor during the pyroclastic‐flow eruption. The large calderas that are more than 10 km in diameter contain original values of approximately 100 km³ of intracaldera pyroclastic flow deposits. These large calderas are similar to the well‐known Valles‐type calderas in their dimensions, although it is uncertain whether their caldera floors are coherent plates or incoherent pieces. Conversely, the small calderas have diatreme‐like subsurface structures. The variety of the caldera volcanoes in this area is caused by the difference in the volume of caldera‐forming pyroclastic eruptions, as the large and small calderas coexisted. The caldera‐forming eruption rates in Late Cretaceous southwest Japan, including the studied area, were similar to those in late Cenozoic central Andes and northeast Honshu arc, Japan, but obviously smaller than those of late Cenozoic intracratonic caldera clusters in western North America and the Quaternary extensional volcanic arcs in Taupo, New Zealand. The widespread Late Cretaceous felsic igneous rocks in southwest Japan were generated by a long‐term accumulation of low‐rate granitic magmatism at the eastern margin of the Eurasian Plate.  相似文献   

东昆仑东段哈拉郭勒-哈图一带中生代的岩石隆升剥露--锆石和磷灰石裂变径迹年代学证据   总被引：4，自引：2，他引：4  

王国灿  向树元JohnI.Garver RobertP.Wintsch MaryRoden-Tice 《地球科学》2003,28(6):645-652

根据对东昆仑地区东段哈拉郭勒—哈图一带不同高度基岩的系列锆石裂变径迹年龄分析，结合磷灰石裂变径迹年龄分析和中酸性侵入岩角闪石压力计分析揭示了东昆仑东段中生代的岩石隆升剥露冷却历史．巴隆哈图一带中酸性侵入岩角闪石压力计分析结果反映晚海西—印支期以来的总体剥露幅度约8～9km，早二叠世至晚三叠世初剥蚀作用极为缓慢，大约为20～40m／Ma．不同高程样品的锆石裂变径迹年龄分析结果揭示了东昆仑地区东段在中晚侏罗世处于缓慢的岩石隆升剥露阶段，其中中侏罗世相对较快，抬升速率77～88m／Ma，晚侏罗世相对较慢，抬升速率小于37m／Ma，且呈减慢趋势，这种减慢趋势反映了早中侏罗世之交强构造抬升期后的逐渐衰退．锆石裂变径迹—磷灰石裂变径迹年龄分析结果反映了中侏罗世以来的剥蚀速率一般不超过55m／Ma，岩石的剥蚀速率与岩石的抬升速率基本为同一量级，中侏罗世—白垩纪剥蚀作用与岩石抬升作用基本处于平衡状态。  相似文献   

焉耆盆地磷灰石裂变径迹分析     

郑求根  张育民  全书进  刘喜杰 《矿物岩石》2003,23(3):69-75

通过裂变径迹分析，研究沉积盆地的古地温，再造沉积盆地的地热史，是近些年来迅速发展的新的研究领域之一。为了深入焉耆盆地古地温场和地质发展史的研究，在焉耆盆地共测试磷灰石裂变径迹分析样品21块，研究焉耆盆地博湖坳陷的古地温场特征，并确定冷却事件发生的时间，利用磷灰石裂变径迹资料计算出地层剥失厚度，对油气的生成运移时期进行分析。  相似文献   

大气降尘TEM观察及其环境矿物学意义   总被引：10，自引：5，他引：10       下载免费PDF全文

陈天虎  徐惠芳 《岩石矿物学杂志》2003,22(4):425-428

在X射线衍射等分析研究基础上，进一步用透射电镜对半封闭室内长期沉积的大气降尘进行观察，提供了合肥地区大气降尘物相组成和各种物相形貌特征信息，揭示合肥地区大气污染物来源占第1位的是地表扬尘，以粘土矿物为标志；占第2位的是来源于大气化学次生气溶胶，主要和SO2、CO2、NOx等气态污染物排放有关，以石膏、碳酸盐和易溶盐类为标志；占第3位的是来源于汽车尾气排放的烟尘，以炭球为标志；占第4位的是来源于燃煤烟尘排放，以球形玻璃珠为特征。TEM调查不仅为合肥地区大气气溶胶颗粒成因、城市大气污染物来源和污染控制对策提供准确资料和依据，而且为确定大气颗粒物来源提供了有效研究方法和物源判别标志。  相似文献   

THE NORTHWARD GROWTH OF THE NORTHEASTERN TIBETAN PLATEAU IN LATE CENOZOIC: IMPLICATIONS FROM APATITE (U-Th)/He AGES OF LONGSHOU SHAN          下载免费PDF全文

LI Jia-yu  ZHENG Wen-jun  WANG Wei-tao  WAN Ying  ZHANG Pei-zhen  WANG Yang 《地震地质》1979,42(2):472-491

Longshou Shan, located at the southern edge of the Alxa block, is one of the outermost peripheral mountains and the northeasternmost area of the northeastern Tibetan plateau. In recent years, through geochronology, thermochronology, magnetic stratigraphy and other methods, a large number of studies have been carried out on the initiation time of major faults, the exhumation history of mountains and the formation and evolution of basins in the northeastern Tibet Plateau, the question of whether and when the northeastward expansion of the northeastern Tibet Plateau has affected the southern part of the Alxa block has been raised. Therefore, the exhumation history of Longshou Shan provides significant insight on the uplift and expansion of the Tibetan plateau and their dynamic mechanism. The Longshou Shan, trending NWW, is the largest mountain range in the Hexi Corridor Basin, and its highest peak is more than 3 600m(with average elevation of 2800m), where the average elevation of Hexi Corridor is 1 600m, the relative height difference between them is nearly 2200m. This mountain is bounded by two parallel thrust faults: The North Longshou Shan Fault(NLSF)and the South Longshou Shan Fault(SLSF), both of them trends NWW and has high angle of inclination(45°~70°)but dips opposite to each other. The South Longshou Shan Fault, located in the northern margin of the Hexi Corridor Basin, is the most active fault on the northeastern plateau, and controls the uplift of Longshou Shan.Due to its lower closure temperature, the lower-temperature thermochronology method can more accurately constrain the cooling process of a geological body in the upper crust. In recent years, the low-temperature thermochronology method has been used more and more in the study of the erosion of orogenic belts, the evolution of sedimentary basins and tectonic geomorphology. In this study, the apatite (U-Th)/He(AHe) method is used to analyze the erosion and uplift of rocks on the south and north sides of Longshou Shan. 11 AHe samples collected from the south slope exhibit variable AHe ages between~8Ma and~200Ma, the age-elevation plot shows that before 13~17Ma, the erosion rate of the Longshou Shan is very low, and then rapid erosion occurs in the mountain range, which indicates that the strong uplift of Longshou Shan occurred at 13~17Ma BP, resulting in rapid cooling of the southern rocks. In contrast, 3 AHe ages obtained from the north slope are older and more concentrated ranging from 220Ma BP to 240Ma BP, indicating that the north slope can be seen as a paleo-isothermal surface and the activity of the north side is weak. The results of thermal history inverse modeling show that the South Longshou Shan Fault was in a tectonic quiet period until the cooling rate suddenly increased to 3.33℃/Ma at 14Ma BP, indicating that Longshou Shan had not experienced large tectonic events before~14Ma BP.
We believe that under the control of South Longshou Shan Fault, the mountain is characterized by a northward tilting uplift at Mid-Miocene. Our results on the initial deformation of the Longshou Shan, in combination with many published studies across the northeastern margin of the Tibetan plateau, suggest that the compression strain of the northeastern margin of the Tibetan plateau may expand from south to north, and the Tibetan plateau has expanded northeastward to the southern margin of the Alxa block as early as Mid-Miocene, making Longshou Shan the current structural and geomorphic boundary of the northeastern plateau.  相似文献   

沉积盆地热演化史研究新进展   总被引：9，自引：0，他引：9  

任战利 《地球科学进展》1992,7(3):43-49

   沉积盆地热历史及其对有机质成熟度的影响是非常活致的研究课题。本文论述了这方面的新进展，其中包括古地温研究办法、盆地热历史类型及热历史重建。作者认为恢复沉积盆地沉积热历史应重视后期地温场的改造。
     相似文献   

“海州式”磷矿床中磷灰石的矿物学研究   总被引：1，自引：0，他引：1  

熊先孝  黄守英 《岩石矿物学杂志》1995,14(3):271-280

“海州式”磷矿床中的磷灰石主要由变质改造再活化、混合岩化交代重结晶而成，有微碳氟磷灰石、氟磷灰石两种，晶胞参数σ０＝９．３６５３－９．３８１９ｎｍ，Ｃ０＝６．８７９７－６．８９３６ｎｍ，晶体化学式为（Ｃａ５．００Ｆ３０．０２Ｓｒ０．０１ＴＲ０．０１）５．０４〔（Ｐ２．９９Ｃ０．０４）３．０３Ｏ１２〕Ｆ０．８０，（Ｃａ４．９４Ｆｅ０．０２Ｍｇ０．０２Ｓｒ０．０１ＴＲ０．０１）５．００〔（Ｐ２．９０〕  相似文献   

裂变径迹分析法研究河北南梁金矿床成矿时代及其热历史   总被引：4，自引：0，他引：4  

袁万明  王世成  王兰芬 《矿物学报》2001,21(2):225-230

河北南梁（下营坊）金矿不同蚀变带中锆石和磷灰石裂变径迹实测年龄为153.9-103.3Ma，其成矿时代应属于燕山早期，成矿时间持续50Ma以上，成矿热历史总体上是早期温度高、冷却快，晚期温度低、冷却慢，转变时间在120Ma左右，转变温度在100℃左右，呈现两期热液成矿过程，第一期热液金矿矿活动发生在150Ma前后，与花岗斑岩体的侵位有关；第二期金成矿作用发生在135Ma前后，与流纹斑岩和岩浆隐爆角砾岩的形成有关。锆石裂变径迹年龄相当于早期成矿时代，磷灰石裂变径迹年龄相当于晚期成矿时代。矿区石英-绢云母化蚀变作用发生时间不仅比钾比蚀变早，而且持续时间亦比钾化长。  相似文献   

矾山磷铁矿成因新解   总被引：2，自引：0，他引：2  

程春 《化工矿产地质》2001,23(4):223-228

在矾山磷铁矿床已有成因认识的基础上 ,通过矿床微量元素Co/Ni值特征、矿床地质构造、巷道地质素描和大地构造背景的分析 ,认为矾山磷铁矿床的磁铁磷灰石岩和磷灰石岩形成时是液态重力分异的正常顺序 :两者近于直立或磷灰石岩上覆于磁铁磷灰石岩之上。而由于张宣馒枝构造与其同期活动 ,产生了这种磁铁磷灰石岩上覆于磷灰石岩的“轻重倒置”现象 ,也形成了Co/Ni值特征的复杂情况。  相似文献