拉萨地块松多榴辉岩的变质演化过程:NCKMnFMASHTO体系中的相平衡关系

拉萨地块松多榴辉岩主要矿物组合为石榴子石、绿辉石、角闪石、多硅白云母、绿帘石、金红石。石榴子石环带不明显,核部成分均一,从核部到边部,镁铝榴石和钙铝榴石含量降低,可能分别记录了榴辉岩峰期及退变质过程信息。绿辉石显示微弱的成分环带,硬玉含量从核部到边部略有升高,部分绿辉石边部发育韭闪石退变质边,反映了在减压过程中外来流体进入体系的过程。多硅白云母具有高的Si含量(3.5~3.6),其中石榴石包体中的多硅白云母相对基质中的白云母有更高的Si值。本文利用Thermocalc变质相平衡模拟软件,结合详细岩相学观察,在NCKMn FMASHTO体系下,模拟松多含多硅白云母榴辉岩的变质演化过程。其中,榴辉岩峰期矿物组合为g+o+law+phn+ru,石榴石核部最大镁铝榴石值和石榴子石包体中多硅白云母最大Si值确定的榴辉岩峰期温压条件约为620℃,32×105Pa,榴辉岩经历了近等温降压的退变质过程。相平衡模拟结果表明拉萨地块松多榴辉岩经历了超高压变质作用过程,并经历了相对快速的折返过程到中部地壳层次。     

对辽宁白云金矿床地质特征及深部找矿的新认识

白云金矿区总体构造为东西走向的线性褶皱构造,金矿体受东西向展布的脆-韧性剪切带控制.辽河群地层是矿源层,矿体赋存于辽河群大石桥组三段及盖县组地层和燕山期的岩脉中,矿化对岩石无明显选择性,矿床具有明显的韧性剪切带特征.硅、钾蚀变带加上黄铁矿化是寻找金矿的最显著标志.深部矿化连续,具较好的找矿前景.提出了深部勘探工作方向和建议.     

对胶南造山带基础地质问题的新认识

:胶南造山带主体是由晚元古代同造山双花岗岩组成的造山带 ,有少量造山前幔源深成岩及造山后碱性花岗岩类。零星分布的地层残片可分为晚太古代胶东岩群 ,早元古代荆山群、粉子山群及震旦纪朋河石岩组。造山带经历了高压相系—中低压相系多期、多相变质作用 ,主要构造形迹为韧性剪切带 ,其次为穹隆构造、弧形构造。胶南造山带可分为北段、中段和南段 3部分 ,北段、中段属于华北板块南部边缘带 ,南段属扬子板块北部边缘带。     

包头—忽鸡沟一带麻粒岩相岩石的矿物学和结晶P-T条件

本文提供了77个石榴石、辉石、角闪石、黑云母和斜长石等单矿物能谱和湿化学分析资料,研究了各种矿物对的分配系数。用二辉石地质温度计估算的变质作用温度为770—860℃,用其他矿物对估算的温度多数在二辉石温度计获得的温度范围内。用Wood的石榴石—斜方辉石地质压力计和Newton—Perkins以及Wells石榴石—斜方辉石—斜长石地质压力计公式估算的变质作用压力为(8—10)×10~8Pa,地热梯度为24.6—27.5℃/km,属低—中压型麻粒岩相。     

Two-stage metamorphic evolution of the Bemarivo Belt of northern Madagascar: constraints from reaction textures and in situ monazite dating

New results on the pressure–temperature–time evolution, deduced from conventional geothermobarometry and in situ U‐Th‐total Pb dating of monazite, are presented for the Bemarivo Belt in northern Madagascar. The belt is subdivided into a northern part consisting of low‐grade metamorphic epicontinental series and a southern part made up of granulite facies metapelites. The prograde metamorphic stage of the latter unit is preserved by kyanite inclusions in garnet, which is in agreement with results of the garnet (core)‐alumosilicate‐quartz‐plagioclase (inclusions in garnet; GASP) equilibrium. The peak metamorphic stage is characterized by ultrahigh temperatures of ～900–950 °C and pressures of ～9 kbar, deduced from GASP equilibria and feldspar thermometry. In proximity to charnockite bodies, garnet‐sillimanite‐bearing metapelites contain aluminous orthopyroxene (max. 8.0 wt% Al₂O₃) pointing to even higher temperatures of ～970 °C. Peak metamorphism is followed by near‐isothermal decompression to pressures of 5–7 kbar and subsequent near‐isobaric cooling, which is demonstrated by the extensive late‐stage formation of cordierite around garnet. Internal textures and differences in chemistry of metapelitic monazite point to a polyphasic growth history. Monazite with magmatically zoned cores is rarely preserved, and gives an age of c. 737 ± 19 Ma, interpreted as the maximum age of sedimentation. Two metamorphic stages are dated: M1 monazite cores range from 563 ± 28 Ma to 532 ± 23 Ma, representing the collisional event, and M2 monazite rims (521 ± 25 Ma to 513 ± 14 Ma), interpreted as grown during peak metamorphic temperatures. These are among the youngest ages reported for high‐grade metamorphism in Madagascar, and are supposed to reflect the Pan‐African attachment of the Bemarivo Belt to the Gondwana supercontinent during its final amalgamation stage. In the course of this, the southern Bemarivo Belt was buried to a depth of >25 km. Approximately 25–30 Myr later, the rocks underwent heating, interpreted to be due to magmatic underplating, and uplift. Presumably, the northern part of the belt was also affected by this tectonism, but buried to a lower depth, and therefore metamorphosed to lower grades.     

湖南寒婆坳矿区热变质煤结构演化及其矿物学特征响应

采用X射线荧光光谱(XRF)、差热分析(DTA)、扫描电子显微镜(SEM)、高分辨透射电镜(HRTEM)、X射线衍射(XRD)和拉曼光谱(Raman)等表征手段对湖南寒婆坳矿区热变质煤的化学组分、物理性质、结构演化与其矿物学特征响应进行了研究。结果表明:岩浆侵入体的热力及构造应力作用促进煤化程度升高逐渐转变为隐晶质石墨,氢、碳原子数目比(H/C)逐渐降低,矿物主要为伊利石、绿泥石、叶蜡石、石英及黄铁矿等;随变质程度增加,真密度升高,孔隙度与电阻率降低;在400℃之后,失重曲线下降缓慢且斜率变小,显示深度裂解与脱落较少。d₀₀₂、L_a、L_c的演化趋势呈非线性变化,显示煤有机大分子结构向石墨化演化的过程中呈现"跃变";隐晶质石墨样品的晶体结构主要为2H型石墨结构,不同程度地含有3R多型,石墨化度为0.47～0.84,石墨晶体轴长a为0.2469～0.2471 nm,c为0.6738～0.6762 nm,晶胞体积V为0.03562～0.03570 nm³,显示靠近岩体晶胞体积减小;随着变质程度升高,L     

Strain rates at high temporal resolution from curved inclusion trails in garnet,Passo del Sole,Central Swiss Alps

Quantitative strain rates at outcrop scale are very difficult to obtain, but they may be estimated from crystals with curved inclusion trails by calculating rotation rates from growth rates and corresponding deflections of the internal foliation. Garnet in a quartzose pelite at Passo del Sole in the central Swiss Alps is extraordinarily valuable for calculation of strain rates during Alpine orogenesis, because the unusual zoning patterns clearly define the kinetics of its nucleation and growth. Complex concentric zoning patterns can be correlated from one crystal to another in a hand sample, based on compositional and microstructural similarities; the ubiquity of these features demonstrates that all garnet crystals nucleated at nearly the same time. Compositional bands whose radial widths are proportional to crystal size provide evidence for growth governed by the kinetics of intergranular diffusion of locally sourced nutrients. Together, these constraints increase the reliability of estimates of rates of garnet growth, and the strain‐rate calculations that depend on them. To obtain growth rates, P–T conditions during garnet crystallization were modelled in a series of pseudosections, and compositional evolution was connected to rates of garnet growth by means of an independently determined heating rate. These growth rates, combined with measured amounts of curvature of inclusion trails, indicate that the time‐averaged strain rate at Passo del Sole during Alpine metamorphism was on the order of 10^?14 s^?1. Strain rates calculated using rotational v. non‐rotational models are similar in magnitude. The constraints on crystallization kinetics also allow direct calculation of strain rates during individual stages of garnet growth, revealing short‐term increases to values on the order of 10^?13 s^?1. These higher strain rates are correlated with the growth of concentric high‐Ca or high‐Mn zones in garnet, which implies that strain softening associated with the transient passage of fluids is responsible for acceleration of deformation during these intervals.     

Apatite recrystallisation during prograde metamorphism,Cooma, southeast Australia: implications for using an apatite – graphite association as a biotracer in ancient metasedimentary rocks

The major patterns in the evolution of life during the Phanerozoic are reviewed. Critical transitions in the evolution of life that reflect increases in ecological complexity are the Cambrian radiation; the Ordovician biodiversification and its subsequent diversification and transition into the Modern Marine Fauna following the Permo-Triassic mass extinction; the colonisation of land, and its subsequent diversification; and the biological colonisation of the atmosphere. This increase in ecological diversity and complexity was often accompanied by increases in morphological complexity, arising, in part, from elaboration of the developmental program. However, it was additionally fuelled by increases in diversification and disparity arising also from morphological simplification in some lineages as developmental program became reduced.     

Correlation of the middle devonian formations of Australia

In the Precambrian rocks west and southwest of the Mount Isa Fault three significant fold generations are recognized. Within individual successions, units containing an early phase of deformation are juxtaposed by a late fault against a sequence that does not share these earlier events.

Many of the large‐scale structures in the Judenan Beds are first‐generation folds, whereas west of the Judenan Beds the area is dominated by second‐generation folds. These two sets of folds are tentatively correlated and are referred to as the Judenan Folds. An earlier set of pre‐Judenan folding is only found in the units west of the Judenan Beds. One phase of the Sybella Granite is also associated with the Judenan folding. Later small‐scale folds associated with a crenulation cleavage are, however, of little regional importance and are commonly found only in zones of highly deformed rocks.     

贵州瓮安玉山煤矿煤质特征及其影响因素

玉山煤矿含煤地层为吴家坪组,可采煤层2层,具有中灰、中等挥发分、高硫分、低磷分、特低—低氯,低砷、高氟,中高发热量的煤质特征,煤类丰富,呈条带状分布。通过对区内沉积环境和煤的变质作用2个方面的分析,阐述了形成煤层高硫、中灰特征的影响因素,解释了煤类分带现象,并指出了主要煤质指标的变化规律。