太行山太古宙变质杂岩中富铝片麻岩的变质作用

太行山太古宙变质杂岩中富铝片麻岩主要分布在湾子岩系的底部，常常与大理岩密切伴生或者以似层状体产于花岗质片麻岩中。依据岩石结构和反应关系将变质作用分为早期、中期和晚期三个阶段。早期矿物组合为Ｇｔ（石榴石）＋Ｓｔ（十字石）＋Ｐｌ（斜长石）＋Ｍｓ（白云母）＋Ｂｉ（黑云母）＋Ｒｕ（金红石）＋Ｑｚ（石英）±Ｋ－ｆｓ（钾长石）；中期矿物组合为Ｇｔ＋Ｇｅｄ（铝直闪石）＋Ｂｉ＋Ｐｌ＋Ｉｌｍ（钛铁矿）＋Ｃｏ（刚玉）＋Ｓｉｌ１（毛发状夕线石）＋Ｑｚ＋Ｋ－ｆｓ±Ｍｓ；晚期矿物组合为Ｈｃ＋Ｋ－ｆｓ＋Ｓｉｌ２（针柱状夕线石）。矿物温度压力计和内部一致性热力学计算结果表明早期矿物组合形成于６８０℃和０．８ＧＰａ左右，刚玉、铝直闪石和毛发状夕线石组合形成于７３０℃～７５０℃和０．７ＧＰａ左右的很窄的Ｐ－Ｔ范围内，夕线石和尖晶石矿物组合的形成温度与前一组合相似或略高，压力偏低。在Ｐ－Ｔ空间上上述矿物组合的演化构成了一条近等温减压（ＩＴＤ型）的ＰＴｔ轨迹。     

基于村落尺度的丘陵山区人口分布特征与规律——以甘肃天水为例

在以农业生产为主的丘陵山地,人口分布具有明显的分散性和差异性。基于村落尺度分析人口分布更接近实际。位于秦岭山地向黄土丘陵区过渡的天水地区,从市域、县域、乡镇到村落,随着分辨尺度的缩小,人口空间分布上的疏密不均现象越突出,变异系数迅速扩大。在7 915个由城镇、村落和居民点构成的斑块上,面积在1.0~10 hm2范围的较小斑块占84.7%,表明分散的、小规模的村落仍是人口分布的主要形式。用非线性函数分析人口密度与村落用地比例、单位面积上的斑块数量、斑块大小的关系,可以较好地揭示人口分布上的一些特征和规律。天水人口分布在地域上明显地表现为河谷高密度区、丘陵中密度区、山地低密度区三种类型,反映人口分布特征的劳作半径和村落间距离在三种类型中都有显著差异。     

Cenozoic extensional stress evolution in North China

Since the beginning of the Cenozoic, north China has been fragmented by intensive intracontinental rifting and extensional tectonics, which resulted in the formation of two extensional domains: the graben systems around the Ordos block in the west and North China Plain in the east. How to link this Cenozoic extensional tectonics to plate kinematics has long been an issue of debate. This paper presents updated results of fault slip data sets collected in different zones in north China and addresses the changes in the direction of extensional stresses over the Cenozoic. A chronology of three successive extensions has been established and provides evidence for constraining the timing and location of either subduction-induced back-arc tectonics along the western Pacific or collision-related extrusion tectonics in Tibet. The oldest NW–SE trending extension occurred concomitantly with the early Tertiary rifting phase, which was initiated in a back-arc setting associated with westward subduction of the Pacific plate under the Asia continent. North China had been subjected, during the Miocene, to regional subsidence with widespread basalt flow, and the direction of extension changed to NE–SW to NNE–SSW, consistent with the spreading direction of the Japan Sea. The dynamic origin of this extension is poorly understood. Since the latest Miocene or earliest Pliocene, north China has been dominated by NW–SE extension resulting in the formation and development of the elongate graben systems around the rigid Ordos block. This extensional phase is accompanied by counterclockwise rotation of blocks such as Ordos, Taihangshan Massif etc., which are bounded to south by the left-lateral strike-slip Qinling fault system. The overall Pliocene-Quaternary deformation in north China accommodates an ESE-ward extrusion of the south China block relative to the Gobi-Mongolia plateau, as the consequence of late-stage India–Eurasia convergence.     

Cenozoic deformation history of the Tancheng–Lujiang Fault Zone, north China, and dynamic implications

Abstract Based on a field analysis of slip vectors from Cretaceous and Tertiary rocks and coupled with rift basin analysis in north China, the Cenozoic deformation history of the Tancheng–Lujiang (Tan–Lu) Fault Zone can be divided into three main phases: early Tertiary normal faulting and northwest–southeast extension; Miocene normal faulting and northeast–southwest to north‐northeast–south‐southwest extension; and Quaternary dextral strike–slip faulting and east‐northeast transpression. The early Tertiary extension, which was responsible for rift basin formation in north China, originated from back‐roll mantle convection induced by westward subduction of the Pacific Plate beneath the Asia continent. The Miocene extension occurred possibly in association with the process of the Japan Sea opening. The Quaternary dextral slip was mainly localized along the middle part of the Tan–Lu Fault Zone and resulted from the far‐field effect of the late‐stage India–Eurasia convergence.     

Compositional Distribution and Growth Mode of Garnet Porphyroblasts during Deformation and Metamorphism

Although porphyroblast microstructures play an important role in structural and metamorphic studies, there are still controversies in the interpretation. The focus is how porphyroblasts grow during deformation and metamorphism. In this paper, we introduce a new approach, the Synchrotron Radiation X-Ray Fluorescence, to a hemi-quantitative interpretation of the growth mode of porphyroblasts. The analysis was done at the Beijing Synchrotron Radiation Facility. The specimens were sampled from metapelite of the Baoyintu Group, northern Urad Middle Banner, Inner Mongolia. The new method is successful for determining the microscopic distribution of trace elements in porphybroblasts. The results support the theory of deformation partition, which has been brought forth by Bell and his colleagues, and demonstrate the existence of porphyroblast growth phases and the growth mode of porphyroblasts by hemi-quantitative mineral chemical analysis. The porphyroblast grows stage by stage in the manner of the distribution     

Zircon U／Pb Dating of Cretaceous Adakitic Volcanic Rocks in the Eastern Part of North Dabie Mountains

1IntroductionMostgeologistshaveacceptedthattheQinling Dabieorogenicbeltistheproductofcontinentaldeepsubduction (Okayetal.,1993;Cong ,B .etal.,1995 ;Hackeretal.,1995 ;DongShuwenetal.,1993) .Butasthebiggest scaleUHPmetamorphicbeltintheworld ,thereactionbetweenthecrustandthemantleatthepost orogenicstageandtheexhumation ,upliftinganddenudationoftheorogenicbeltarethecomplexdynamicprocesses .ItwasreportedpreviouslythatsomeCretaceousvolcanicrocksexistinthemiddleoftheDabieMountains (GuanYuncaiet…     

大别造山带东部假玄武玻璃及其围岩的K-Ar和^40Ar-^39Ar年龄及地质意义

发育在大别造山带东部的假玄武玻璃是区域内NE-SW向断裂带快速滑移形成的构造岩。地质产状、显微构造及岩石化学研究表明，这些假玄武玻璃主要由超碎裂岩化作用所形成。假玄武玻璃及围岩的全岩(包括部分单矿物)K-Ar年龄测定表明，大别造山带的假玄武玻璃形成于81～93Ma之间。本文同时测定了叠加在假玄武玻璃基质之上的多硅白云母的激光^40Ar／^39Ar年龄为78．9Ma。显微构造及所获得的年龄数据显示，这些沿NE-SW向断裂发育的假玄武玻璃是在晚白垩世(80～90Ma)时期伴随着大别造山带整体隆升过程形成的，而与早期板块俯冲过程无关。同时，不同定年方法在数据上的一致性还表明，全岩K-Ar方法在确定某些假玄武玻璃及含假玄武玻璃的断裂构造年代时，可能仍然是一种行之有效的的方法。     

Contrasting provenance of Late Archean metasedimentary rocks from the Wutai Complex, North China Craton: detrital zircon U–Pb, whole-rock Sm–Nd isotopic, and geochemical data

Detrital zircon U–Pb ages, whole-rock Nd isotopic, and geochemical data of metasedimentary rocks from the Wutai Complex in the Central Zone, North China Craton, have been determined. Compositionally, these rocks are characterized by a narrow variation in SiO₂/Al₂O₃ (2.78–3.96, except sample 2007-1), variable Eu anomalies, spanning a range from significantly negative Eu anomalies to slightly positive anomalies (Eu/Eu* = 0.58–1.12), and positive ε _Nd (t) values (0.1–1.97). The 18 detrital zircons of one sample yielded age populations of 2.53 Ga, 2.60 Ga, and 2.70–2.85 Ga. Geochemical data reveal intermediate source weathering, varying degrees of K-metasomatism in the majority of these metasedimentary rocks, whereas other secondary disturbances seem to be negligible. Detailed analysis in detrital zircon U–Pb geochronology, whole-rock Nd isotope, and geochemistry shows that these metasedimentary rocks are derived from a mixed provenance. The predominant derivation is from the late Archean granitoids and metamorphic volcanics in the Wutai Complex, and there is also input of older continental remnants, except TTG gneisses, from the Hengshan and Fuping Complexes. The sediments were probably deposited in fore-arc or/and intra-arc basins within an arc system.     

吉林四方甸子钼矿床成岩成矿时代及岩石地球化学特征

吉林四方甸子钼矿床是一新发现的石英脉型钼矿床,矿床产于二长花岗岩中。矿床成矿包括无矿石英脉阶段、石英-辉钼矿-黄铁矿阶段和石英-碳酸盐化阶段。通过对矿区内花岗质岩石进行LA-ICP-MS同位素测年,获得花岗闪长岩成岩年龄为（170.0±1.0） Ma,二长花岗岩成岩年龄为（179.0±1.0） Ma。对含矿石英脉中辉钼矿Re-Os同位素测年分析,获得辉钼矿模式年龄值为（175.0 ± 2.6）～（176.5 ± 2.6）  Ma,加权平均值为（176.1 ± 1.1） Ma,等时线年龄为（176.6 ± 4.2）  Ma,表明四方甸子钼矿床形成于早侏罗世晚期。岩体w(SiO₂)为66.17%～76.60%,w(Na₂O)和w(K₂O)分别为3.15%～5.40%和2.42%～5.42%,里特曼指数σ为2.17～2.93。稀土元素分布形式呈右倾型,轻、重稀土元素分馏明显。微量元素总体显示相对富集Rb、Ba、Th、U等大离子亲石元素（LILE）,亏损Nb、Ta、Ti、P等高场强元素（HFSE）。综合分析表明,岩石为弱过铝质I型花岗岩。成岩成矿动力学背景为燕山早期古太平洋板块向欧亚大陆俯冲作用的大陆边缘环境。     

大兴安岭北部比利亚谷铅锌矿黄铁矿Re-Os同位素年龄及He-Ar同位素地球化学特征

比利亚谷铅锌矿位于海拉尔-根河中生代火山盆地北西缘的得尔布干成矿带.该矿床赋存于上侏罗统满克头鄂博组酸性火山岩中,受NW向断裂构造控制,主矿体呈脉状产出.由于缺少适合传统放射性同位素定年的矿物,其成矿时代未得到很好的限定,制约了对矿床成因的认识.本文采用矿床中与矿石矿物密切共生的黄铁矿Re-Os同位素定年技术对比利亚谷...