宿松变质杂岩中石榴石-蓝晶石-硬绿泥石片岩形成条件及时限研究     

石永红  王娟  聂峰  曹晟  康涛 《岩石学报》2016,32(2):493-504

宿松变质杂岩因变质程度较低,岩性较为繁杂,故其变质演化及年龄一直缺乏系统性和全面性研究,这很大程度上影响了人们对大别造山带结构框架和演化的深入理解。本次研究主要针对太湖-马庙断裂和柳林-缺月岭-山龙断裂之间的宿松变质杂岩进行了综合细致的分析,确定了特征性的高压岩石——石榴石-蓝晶石-硬绿泥石片岩的存在。利用THERMOCALC的Average P-T法,确定了石榴石-蓝晶石-硬绿泥石片岩的峰期变质温压条件为T=551~569℃和P=1.96~2.47GPa,属于高压榴辉岩相。LA-ICP-MS锆石U-Pb定年显示该岩石的峰期变质年龄为242.2±2.0Ma,退变质年龄为216.2±6.6Ma。结合区域地质调查和前人的研究成果,该岩石可能普遍存在于这两断裂之间,并暗示了这两断裂之间的块体经历了高压变质作用,其应当从宿松变质杂岩中剥离出来。本文在此暂定名为大山-麻石沟高压块体,并建议宿松变质杂岩的北界止于柳林-缺月岭-山龙断裂。  相似文献   

Dynamic melting of the Precambrian mantle: evidence from rare earth elements of the amphibolites from the Nellore–Khammam Schist Belt, South India     

K. Vijaya Kumar  M. Narsimha Reddy  C. Leelanandam 《Contributions to Mineralogy and Petrology》2006,152(2):243-256

The Nellore–Khammam Schist Belt (NKSB) in South India is a Precambrian greenstone belt sited between the Eastern Ghats Mobile Belt (EGMB) to the east and the Cratonic region to the west. The belt contains amphibolites, granite gneisses and metasediments including banded iron formations. Amphibolites occurring as dykes, sills and lenses—in and around an Archaean layered complex—form the focus of the present study. The amphibolites are tholeiitic in composition and are compositionally similar to Fe-rich mafic rocks of greenstone belts elsewhere. The NKSB tholeiites show highly variable incompatible trace element abundances for similar Mg#s, relatively constant compatible element concentrations, and uniform incompatible element ratios. Chondrite-normalized REE patterns of the tholeiites range from strongly LREE depleted ((La/Yb) _N = 0.19) to LREE enriched ((La/Yb) _N = 6.95). Constant (La/Ce) _N ratios but variable (La/Yb) _N values are characteristic geochemical traits of the tholeiites; the latter has resulted in crossing REE patterns especially at the HREE segment. Even for the most LREE depleted samples, the (La/Ce) _N ratios are > 1 and are similar to those of the LREE enriched samples. There is a systematic decrease in FeO^t, K₂O and P₂O₅, as well as Ce and other incompatible elements from the LREE enriched to the depleted samples without any variation in the incompatible element ratios and Mg#s. Neither batch and fractional melting, nor magma chamber processes can account for the non-correlation between the LREE enrichment and HREE concentrations. We suggest that dynamic melting of the upper mantle is responsible for these geochemical peculiarities of the NKSB tholeiites. Polybaric dynamic melting within a single mantle column with variable mineralogy is the likely mechanism for the derivation of NKSB tholeiitic melts. It is possible that the NKSB tholeiites are derived from a source with higher FeO/MgO than that of present day ridge basalts.  相似文献   

Laboratory simulation of the salt weathering of schist: 1. Weathering of schist blocks in a seasonally wet tropical environment     

Tony Wells  Philip Binning  Garry Willgoose  Greg Hancock 《地球表面变化过程与地形》2006,31(3):339-354

Data describing sediment generation focusing on the temporal evolution of size gradation are required for the prediction of long‐term landform evolution. This paper presents such data for the salt weathering of a quartz‐chlorite schist obtained from the Ranger Uranium Mine in northern Australia. Rock fragment samples are subjected to three different climate regimes: (1) a dry season climate; (2) a wet season climate (both based on observations at the Ranger site); and (3) an oven‐drying sequence designed to test the sensitivity of the weathering process by exposing the rocks to more extreme temperatures. Two MgSO₄ salt solutions are applied, one being typical of wet season runoff and the other a more concentrated solution. Salt solution is applied daily in the wet season experiments and once only at the beginning of the dry season experiments. Results of the experiments reveal four stages of weathering. The kinetics of each stage are described and related to the formation of sediment of different sizes. Wet season climate conditions are shown to produce greater moisture variability and lead to faster weathering rates. However, salt concentrations in the wet season are typically lower and so when climate is combined with observed salt concentrations, the dry and wet season experiments weather at approximately equal rates. Finally, small variations in rock properties were shown to have a large impact on weathering rates, leading to the conclusion that rock weathering experiments need to be carefully designed if results are to be used to help predict weathering behaviour at the landscape scale. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

An investigation into the relationship between salt weathering debris production and temperature     

Alan Paul Davison 《地球表面变化过程与地形》1986,11(3):335-341

An investigation using laboratory simulation has been made using air temperature data for Tunisia, Antarctica, and southwest England. An experiment with a 50 cycle run produced results which showed significantly greater debris production in the Antarctica and Tunisian simulations than in the southwest England simulation. Using X-ray analysts to determine salt penetration, an inverse relationship between salt penetration and debris production was seen to exist. This could be the result of evaporation in the Tunisian simulation and rapid freezing in the Antarctic simulation, concentrating salts in the upper layers of the rock samples. In the southwest England simulation, no freezing, and relatively high humidities allowed greater penetration, thus distributing an equal input of salt over a greater area. The author tentatively suggests the possible existence of a parabolic relationship between salt weathering and temperature.  相似文献   

福建屏南黛溪铅锌矿床地质特征与成因   总被引：3，自引：0，他引：3  

马春 《福建地质》2002,21(1):21-26

福建屏南黛溪铅锌矿床形成了火山活动频繁的断陷带中，矿体产于火山基底“构造窗”震旦纪龙北溪组地层中，矿化受绿片岩相控制，矿体呈似层状，与围岩产状一致，矿石具特殊的结构和构造，矿物组分简单，品位低，规模较大，硫主要来源于花岗质岩浆，铅来源于地壳，有陆源铅混染，表现为“层控型”矿床特征和多期次地质作用的叠加改造。  相似文献   

木兰山蓝片岩中斜黝帘石—低铁绿帘石连生体的确定   总被引：1，自引：1，他引：1  

赵文俞  牟善斌等 《岩矿测试》2002,21(1):29-32

电子探针和光学显微镜联合分析表明，木兰山蓝片岩中存在斜黝帘石－低铁绿帘石连生体。界面区Fe、Al元素的线扫描曲线研究表明，（Fe,Al)类质同象替代为连生体界面共晶膜的形成机制。木兰山蓝片岩中斜黝帘石－低铁绿帘石连生体的确定，说明电子探针和光学显微镜联合分析可有效确定光学性质和化学成分均相近的微细粒连生体的组成矿物，其结果对认识木兰山蓝片岩的变质演化具有指示意义。  相似文献   

Mechanism of creep movement caused by landslide activity and underground erosion in crystalline schist, Shikoku Island, southwestern Japan   总被引：12，自引：0，他引：12  

G. Furuya  K. Sassa  H. Hiura  H. Fukuoka 《Engineering Geology》1999,53(3-4):311-325

The mechanism of creep movement of the Zentoku landslide in crystalline schist has not been studied in detail because of the steepness of the slope, very slow movement, low population density and complex topographic and geologic characteristics. Sassa et al. (1980: Proc. INTERPRAEVENT 1, 85–106) and Sassa (1984: Proc. 4th International Symp. on Landslides, Toronto, vol. 2, pp. 179–184; 1985. Geotechnical classification of landslides, Proc. 4th International Conference and Field Workshop on Landslides, Tokyo, pp. 31–40; 1989: Landslide News, Japan Landslide Society, No. 3, pp. 21–24) monitored landslide movement and groundwater level at the Zentoku landslide on Shikoku Island, southwestern Japan, and suggested that the mechanism may be caused by underground erosion. To study the influence of underground erosion at this site, continual monitoring of suspended sediment and water discharge from a groundwater outlet (i.e. a spring) was implemented. The locations of groundwater flow paths were determined, as were the amounts of discharged sediment. Slope deformation was monitored by means of a borehole inclinometer. The conclusions were as follows: (1) the flow paths were found to be on or above the shear zones in which underground erosion has occurred; (2) in addition to being a result of precipitation and groundwater discharge, sediment discharge is affected by landslide activity; and (3) the mechanism of creep movement is an interrelated chain process that combines underground erosion caused by landslide activity with landslide activity caused by underground erosion. Thus, landslide activity increases erosion susceptibility and transportation of soils within the mass, and underground erosion causes instability of the landslide mass, in turn.

This mechanism can explain the observed phenomenon that the Zentoku landslide not only moves actively during heavy rain, but also continues to creep throughout the year.  相似文献   

Early Cretaceous tectonic events implied in the time-lag between the age of radiolarian chert and its metamorphic basement in the Bantimala area, South Sulawesi, Indonesia     

Koji  Wakita  Munasri  Jan  Sopaheluwakan  Iskandar  Zulkarnain Kazuhiro  Mlyazaki 《Island Arc》1994,3(2):90-102

Abstract The Bantimala Complex of South Sulawesi consists mainly of mélange, chert, basalt, ultramafic rocks and high pressure type metamorphic rocks. Well-preserved radiolarians were extracted from 10 samples of chert, and K-Ar age dating was done for muscovite from five samples of schist of the Bantimala Complex. The radiolarian assemblage from chert is assigned middle Cretaceous (late Albian-early Cenomanian) age, while the K-Ar age data from schist range from 132 Ma to 114 Ma except for one sample with rare muscovite. The radiolarian chert is unconformably underlain by schist in the Bantimala Complex. The stratigraphie relationship and the time lag of these two kinds of age data from chert and underlying schist suggest short-time tectonic events immediately followed by a quick waning tectonism in this region during the Albian-Cenomanian transgression.  相似文献   

Talc-phengite-albite assemblage in piemontite-quartz schist of the Sanbagawa metamorphic belt, central Shikoku, Japan     

J. Izadyar  T. Hirajima†  D. Nakamura‡ 《Island Arc》2000,9(1):145-158

Abstract The talc (Tlc) + phengite (Phn) + albite (Ab) assemblage is newly confirmed in MnO^total-rich (1.65 wt% in average) piemontite-quartz schists from the intermediate- and high-grade part of the Sanbagawa belt, central Shikoku, Japan. Talc is in direct contact with Phn, Ab and chlorite (Chl) with sharp boundaries, suggesting that these four phases mutually coexist. Other primary constituents of the Tlc-bearing piemontite-quartz schist are spessartine, braunite, hematite (Ht), crossite/barroisite and dolomite. Phlogopite (Phl) rarely occurs as a later stage mineral developing along the rim of Phn. The studied piemontite-quartz schist has mg# (= Mg/(Mg + Fe²⁺)) ~ 1.0, because of its high oxidation state. Schreinemakers' analysis in the KNMASH system and the mineral assemblage in the Sanbagawa belt propose a possible petrogenetic grid, in which the Tlc–Phn assemblage is stable in a P-T field surrounded by the following reactions: lower-pressure limit by Chl + Phl + quartz (Qtz) = Phn + Tlc + H₂O as proposed by previous workers; higher-pressure limit by glaucophane + Qtz = Tlc + Ab + H₂O; and higher-temperature limit by Tlc + Phn + Ab = Phl + paragonite + Qtz + H₂O. Thermodynamic calculation based on the database of Holland & Powell (1998) , however, suggests that the Tlc–Phn stability field defined by these reactions is unrealistically limited around 580–600 °C at 11.6–12.0 (± 0.7) kbar. Schreinemakers' analysis in the KNMA-Fe³⁺-SH system and the observed mineral assemblage predict that Chl + crossite = Tlc + Ab + Ht + H₂O is a preferable Tlc-forming reaction in the intermediate-grade part of the Sanbagawa belt and that excess Ab + hematite narrows the stability field of the Tlc–Phn assemblage.  相似文献   

颗粒破碎对绢云母片岩强度和变形影响的试验研究     

秦尚林  杨兰强  陈荣辉  陈善雄 《岩土力学》2014,35(11):3086-3092

为进一步弄清颗粒破碎对软岩粗粒料强度、变形的影响,开展2组不同初始干密度下的绢云母片岩粗粒料的固结排水三轴试验,分析了绢云母片岩粗粒料颗粒破碎规律,并探讨了颗粒破碎对绢云母片岩粗粒料力学性质的影响。结果表明,绢云母片岩粗粒料相对破碎率随围压的增加而增大,但颗粒破碎增幅速率受初始干密度影响较大,颗粒破碎与围压之间的关系可用线性关系描述;由于初始孔隙率的影响,使得试样在同一应力水平下高密度试样颗粒破碎明显高于低密度试样;颗粒破碎对高密度试样抗剪强度降低的影响高于低密度试样,导致两种干密度试样的应力-应变曲线在某处出现相交,最终出现初始密度低的试样抗剪强度大于初始密度高的试样抗剪强度的现象;高密度试样孔隙率较小,其剪胀因子一直保持在1附近,而低密度试样孔隙率较大,受颗粒破碎和剪胀的影响迟缓一些,低密度试样体变较高密度要大些,但整体上由于颗粒破碎和剪胀的影响,绢云母片岩粗粒料的体变均不大。  相似文献