确定火山岩的喷发期次是重建火山喷发相关的第四纪环境、研究晚新生代地球动力学和预测火山喷发危险性的前提.激光40Ar/39Ar年代学方法对年轻火山岩样品的定年有明显的优势,具有自动化测试稳定、本底低、高灵敏度等特点,适用于年轻火山岩样品的定年工作.文章采用激光40Ar/39Ar年代学方法对腾冲火山岩区主要岩石单元进行了精细的年代学研究,通过常规的数据处理得到了腾冲火山喷发的时限为0.025～5.1Ma.但年轻火山岩定年因放射成因的40Ar含量极少,偶然因素较多,数据的稳定性较差,甚至得出偏差很大的年龄结果,其分期结果值得商榷.另外,传统分期方法缺乏统一的时间尺度标准,无法对腾冲火山喷发进行严格的时间限定,导致对期次划分认识的分歧.文章尝试引入新的数学模型,对13件样品一共378个年龄测试值进行了重新分期,得到了包含3个波形曲线、彼此独立的表观年龄概率分布图,利用高斯数学模型对波形进行分析,分别对确认的3个正态波形涵盖的年龄数据进行等时线年代学计算,很好地限定了腾冲火山的3期喷发,分别为上新世((3.78±0.04)Ma)、中更新世早期((0.63±0.03)Ma)和中更新末期到晚更新世早期((0.139±0.005)Ma).这3期喷发时限具有相同的实验精度和时间尺度,降低了年龄数据的误差和偶然性,能准确地限定和代表腾冲火山的整体喷发分期.

Reconstruction of Quaternary environments, late Cenozoic geodynamics and evaluation of volcanic hazards, all depend on the precise delineation of eruptive stages. In recent years, laser 40 Ar/ 39 Ar dating methods have been widely used for dating young volcanic rocks, given their stable automated testing process, very low background level and high sensitivity, which meet the requirements for precise dating of young samples. This paper applied high-precision laser 40 Ar/ 39 Ar dating to the main volcanic units in the Tengchong area and obtained ages in the range of 0.025–5.1 Ma using conventional data processing methods. However, conventional dating highlighted issues related to very low radiogenic 40 Ar content, accidental errors and poor data stability, which led to huge age deviations. Moreover, lacking a unified timescale, conventional methods were unable to strictly define the stages of the Tengchong volcanic eruptions, leading to ongoing controversy. In this study, we applied a Gaussian mathematical model to deal with all 378 original ages from 13 samples. An apparent age-probability diagram, consisting of three independent waveforms, have been obtained. The corresponding isochron ages of these three waveforms suggest there were three volcanic eruptive stages, namely during the Pliocene (3.78±0.04 Ma), early Middle Pleistocene (0.63 ±0.03 Ma) and late Middle Pleistocene to early Late Pleistocene (0.139±0.005 Ma). These results accurately define eruptive stages in the Tengchong area.

The authors measured root morphological and architectural traits of 22 different dominant plant species across 16 Inner Mongolia grassland sites along soil water gradients, and analyzed the response of these root traits (diameter, length, SRL, RTD, BrIntensity and BrRatio) to four environmental factors (MAT, MAP, Soil N and Soil C). The results showed that variation of absorptive root diameter, tissue density and specific root length among different species was 7, 9, and 15 times, respectively. There was a significant positive correlation between root diameter and lateral root length, but negative correlation between root diameter and root branching intensity. Responses of both absorptive and non-absorptive roots to precipitation and soil nitrogen were species-specific. When using different combinations of root traits to describe plant adaptation strategies, different species’ root traits respond to environmental changes with different degrees and direction of variation, resulting in a diversity of plant adaptation strategies.

Crustal deformation can be closely associated with Earth surface process. A combined approach of geological mapping, petrology, geochronology and structural analysis of the Taili Beach, North China, reveals a detailed magmatic and deformation history associated with orogenesis and intensive exhumation. Three groups of rocks developed along the Taili beach, including gneisses, mylonites and massive granites. Gneisses recorded near E-W-trending rootless fold and subvertical gneissosity of lower structural level. Mylonites exposed along ENE-trending ductile shear zone, with porphyritic protomylonite permeated into gneiss of lower-middle structural level. Gneisses formed in Neo-Archean to Paleo-Proterozoic, were modified by similar to 230-220 Ma magmatic and deformation event. This tectonic event is related to the Indosinian orogenesis, leading to the re-melting of the lower crust Archean rocks and intense deformation forming subvertical gneissosity and sinistral mylonites zones within N-S direction compression. The structural analysis indicates that rootless fold Si formed at the depth of similar to 24-20 km, gneissosity formed at similar to 18-15 km, while mylonite foliation S-2 formed at similar to 12-10 km and felsic leptynite formed at similar to 8-7 km. Massive granites intruded into gneisses and mylonites at depth <3 km (not late than 159Ma). The deformation sequence indicates that the Tail crust uplifted nearly 20 km during the similar to 230-220 Ma to similar to 159 Ma. The intensive exhumation in orogenesis may be related to earth surface erosion process.

The Bikou terrane lies on the northwestern margin of the Yangtze Block.It comprises pelitic rocks in the north and mafic-intermediate volcanic rocks in the south.Rocks in the north metamorphosed into phyllite and mica schist,while rocks in the south experienced greenschist blueschist facies metamorphism.Presently,there are no detailed analyses on the deformation sequence and regional metamorphism of the Bikou terrane;geochronological constraints for regional metamorphism are also lacking.As a result,nature of the Bikou terrane and age of regional metamorphism and tectonic settings are not known,causing controversy over the orogenies of West Qinling and Longmen Mountain.Here,after detailed field study and structural analysis,we divided the Bikou terrane deformation sequence into three stages,D1,D2 and D3.D1 is marked by tight fold,foliation S1 and mineral lineation L1;D2 is normal ductile shear dipping to the south,transforming thrust faults and resulting in formation of Jurassic half-graben basins;and D3,formed in the sinistral strike-slip thrust in the Himalayan,is characterized by brittle deformation.In this study,we obtained UPb zircon age of 227.2± 6.2 Ma from deformed felsic veins in the Bikou terrane.Since the undeformed intrusive plutons after D1 deformation yielded age of 226-215 Ma in previous studies,the age of regional metamorphism in the Bikou terrane is constrained at ca.220 Ma.Therefore we infer that,D1 formed during subduction and collision between the North and South China blocks in the Late Triassic,when regional metamorphism of the Bikou terrane occurred,and D2 and D3 were related to eastward expansion of the Tibetan Plateau.

从课程需要与行业需求出发确定本案例选题为"网购童装顾客满意度分析";针对研究内容,进行学生参与的原创性案例编写准备,包括问卷设计和调查;利用Execl和SPSS软件进行数据分析,完成案例编写.

Located in the Huzhou-Anji volcanic basin in the northeastern margin of Zhejiang-Ganzhou volcanic rock belt,the volcanic/subvolcanic rocks consist dominantly of intermediate-felsic to felsic rocks with minor intermediate component and lack of mafic component,and represent a intermediate-felsic magmatic rocks series.The rocks are lithochemically characterized by high-K and rich alkali,suggesting that intermediate rocks belong to shoshonite series and the intermediate-felsic and felsic rocks belong to high potassium calc-alkaline series.In geochemistry,the volcanic rocks in the basin are enriched in large-ion lithophile elements (LILE) and light rare earth elements (LREE) and depleted in high field strong elements (HFSE) such as Nb,Ta and Ti.Major and trace elements variation regulation of the volcanic rocks reveals that fractional crystallization is the main mechanism of the magma evolution in the basin.Different mineral facies is produced at different stage of magma evolution,with plagioclase being the key mineral of fractionation and crystallization.Hornblende may be an important fractionation mineral during the intermediate to intermediate-feslic magma evolution,and K-feldspar and biotite minerals also play an important role in the fractionation of intermediate-felsic to felsic rocks.Our dating results show that the LA-ICP-MS zircon U-Pb ages of three episodes of volcanic activities in the basin are around 128～130 Ma,which fall within the error range,indicating that the main volcanic activities lasted for very short time.The SHRIMP zircon U-Pb dating yields an age of 136±1 Ma for the trachyandesite agglomerates,probably indicating small-scale weak mafic volcanic activities at the initial stage of the basin.It can be speculated that the Huzhou-Anji volcanic basin developed in a post-orogenic environment in the active continental margin,the magma formation was probably controlled by lithosphere delamination or subduction slab breakoff,with parent magma formed by partial melting of mafic lower crust material and with barely mantle material involvement,and the resulting andesitic-dacitic magma experienced strong fractional crystallization at the shallow magma chamber.

庐枞火山岩盆地南侧的钾质侵入岩带由正长岩-石英正长岩-正长花岗岩组成,以石英正长岩为主.它们的形成时间介于123～130 Ma之间,峰值约为126 Ma,其中正长岩和石英正长岩的形成时间稍早,而正长花岗岩的形成时间略晚.整个钾质侵入岩带的侵位时间晚于庐枞盆地内的橄榄玄粗质火山作用约4～7 Ma,也是长江中下游地区除最东段的宁镇地区外中生代最晚的岩浆活动产物之一.地球化学上,该钾质侵入岩带以高钾、富碱、富集Rb、Th、U、K等强不相容元素和轻稀土元素、亏损高场强元素Nb、Ta和Ti为特征.它们的母岩浆主要是由富集型上地幔部分熔融形成的,从正长岩经石英正长岩到正长花岗岩的演化主要受矿物的分离结晶作用控制,地壳物质同化所起的影响不大.但与同样来自富集型上地幔部分熔融的庐枞盆地内火山杂岩的母岩浆相比,前者的母岩浆来源深度可能更大些或其中包含了更多来自软流圈地幔的组分.两者的演化路径也完全不同,钾质侵入岩带的母岩浆除经历过高压下的分离结晶作用外,晚期在低压下还经历过长石为主,可能还有黑云母的分离结晶,甚至上地壳物质一定程度的混染作用;而盆地内火山杂岩的母岩浆低压下矿物的分离结晶作用及上地壳物质的混染都不明显.庐枞盆地南缘的富钾侵入岩与盆地内的火山杂岩一样,地球化学上都具有明显的大陆弧的特征,暗示它们的岩浆源区可能形成于俯冲带环境,意味着扬子地块北缘先前(推测为古元古代晚期)曾发生过俯冲作用,上地幔的交代富集可能就与这次的俯冲作用有关.

长江中下游地区晚中生代橄榄玄粗岩系列火山岩发育在宁芜、庐枞、溧水和怀宁四个火山岩盆地内,该系列的火山岩地球化学性质上以相对富碱、高K、明显富集Rb、Th、U、K等强不相容元素和轻稀土元素,亏损高场强元素Nb、Ta和Ti为特征.Ba和Sr的特征在不同盆地内随岩性的不同表现各异,表明斜长石的分离结晶可能在这些盆地内岩浆演化过程中起着一定的作用.这些盆地内橄榄玄粗岩系列火山岩的部分地球化学性质(如Ce/Yb比值)与大多数发育在大陆环境下的橄榄玄粗岩系列岩石不同,而类似于大洋岛弧环境内的同类岩石,可能意味着区内由于岩石圈的减薄,软流圈地幔上涌到了相对较浅的部位,控制源区部分熔融的主要是尖晶石相地幔岩.这些火山岩的Sr、Nd同位素组成总体处于扬子克拉通岩石圈地幔附近,指示它们的母岩浆主要是由富集的岩石圈地幔部分熔融形成的.但盆地所处的构造位置对岩浆的性质也有显著的影响,指示地壳基底物质的混染也不同程度存在.区内榄玄粗岩系列火山活动持续的时间很短,主要集中在约128～134 Ma左右,峰值约130Ma,其成因的动力学机制可能与晚中生代发生在中国东部的岩石圈减薄事件有关,橄榄玄粗岩系列火山岩盆地所在地带对应着长江中下游地区岩石圈减薄的中心部位.

The Luzong volcanic basin has a unique tectonic background, being located at the northeastern margin of the Yangtze craton and the foreland of the Dabie–Sulu orogen, near the intersection of the renowned Tanlu and Yangtze River faults. The volcanic and subvolcanic rocks in the basin are characterized by high potassium contents and are rich in alkali elements, and belong to a typical shoshonite series. Geochemically, these rocks are depleted in high field strength elements such as Nb and Ta, and enriched in highly incompatible elements such as Rb, Th, U, K, and light rare earth elements. Nd and Sr isotope compositions, combined with elemental geochemical characteristics, indicate that the parental magmas were formed mainly by partial melting of enriched subcontinental lithospheric mantle. The magmas underwent minor or negligible contamination by upper crustal rocks or fractional crystallization at low pressures (i.e., <1.5GPa). Nevertheless, variation trends for major and trace elements indicate that these shoshonitic mantle-derived magmas experienced fractional crystallization at high pressures (i.e., above the stability field of plagioclase, >1.5GPa), dominated by the removal of clinopyroxene and Fe–Ti oxides. The volcanic rocks of the Luzong Basin can be divided into four formations, which, from early to late, are the Longmenyuan, Zhuanqiao, Shuangmiao, and Fushan Formations, each separated by clear gaps in eruptive activity. In this study, we obtained zircon U–Pb SHRIMP ages from two subvolcanic samples from the Longmenyuan and Zhuanqiao Formations, which yield emplacement ages of 132±1Ma and 131±1Ma. These data, combined with ages reported by other workers, show that the duration of volcanism in the Luzong Basin (and the whole middle and lower Yangtze River reaches) was very short (⩽8Ma). We consider that in the Early Cretaceous the foreland area of the Dabie orogenic belt was under extension, influenced by the relative motion of the Pacific and Eurasian plates, and by sinistral displacement along the Tanlu Fault. At this time, rapid mechanical delamination of thickened lithosphere caused lithospheric thinning and resultant asthenospheric upwelling in the middle and lower Yangtze River region and the Dabie orogenic belt. These deep geological and tectonic events in turn produced the shoshonite volcanic rocks in the Luzong Basin.

Tuite has been suggested as a potential reservoir for trace elements in the deep mantle, but no evidence confirms this supposition. By using a natural apatite as starting material, the trace-element-bearing tuite large crystals were obtained under high-pressure and high-temperature conditions (15 GPa and 1800 K). X-ray diffraction pattern and Micro-Raman spectrum of the run product confirm that tuite was synthesized. The concentrations of trace elements in tuite crystals were analyzed by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The rare earth element patterns of tuite show enrichment of light rare earth elements relative to heavy rare earth elements. Tuite shows high concentrations of Th and Sr, and negative anomalies of Rb, Nb, and Hf. The results show that tuite can accommodate a large amount of trace elements. Tuite might be an important host to accommodate trace elements if there is much apatite subducted into the deep mantle.

The Suizhou-Zaoyang area (northern margin of the Yangtze Craton), the least affected area of the whole Qinling-Tongbaishan-Dabieshan-Sulu orogen and their foreland by the deep subduction of the Yangtze Craton beneath the North China Craton and concomitant HP-UHP metamorphism during Triassic, relatively well preserved Precambrian basement of the northern Yangtze Craton. These low-grade metamorphosed Precambrian rocks not only provide an ideal opportunity to study the palaeo-tectonic setting of the northern Yangtze Craton, but also are rare-references for resuming protolithes of the metamorphic complex in the orogen. The Precambrian rocks exposed here include Neoproterozoic volcanic-sedimentary rock series (Suizhou Group) and voluminous Neoproterozoic ultramafic-mafic sill swarms. In this work, we used LA-ICP-MS zircon U-Pb technique dating detrital zircons from the metasedimentary samples of the Suizhou Group, yielding results as follow; (1) The youngest age of detrital-zircon from the metasediments of the Suizhou Group is about 720Ma, which means that the formed age of the Suizhou Group was mainly later than this time; (2) Zircon grains with ages from about 700Ma to 1000Ma are maximum detrital zircon group, with peak value at about 800Ma, showing that the magmatic rocks formed in Neoproterozoic era, especially medium to late stage of the Neoproterozoic, were foremost source of the Suizhou Group; (3) There are many zircon grains with ages from 1700Ma to 2100Ma, showing that the magmatic rocks formed in the medium to late stage of the Paleoproterozoic were also one of important sources; (4) Existing of detrital-zircon with ages of early stage of Paleoproterozoic and Archaean imply that this era of stratum may exist in the northern margin of the Yangtze Craton.

The volcanic rocks in Huaining basin, one of a series of late Mesozoic volcanic basins developed in the Middle -lower Yangtze region, are characterized by high K and rich alkali and mainly belong to typical shoshonitic series. However, bimodal volcanic association appeared at the late stage of volcanism in Huaining basin. The volcanic rocks in the basin are all depleted in high-field-strong-elements (HFSE) such as Nb and Ta, and enriched in strong incompatible elements such as Rb, Th, U and K as well as light rare earth elements (LREE). In this study, the authors used SHRIMP and LA-ICP-MS zircon U-Pb technique to date the samples from Pengjiakou Formation and early volcanism respectively in Huaining basin, and obtained emplacement ages of 129.411.6 Ma and 131.6±0.6 Ma respectively. The age of 122.3±0.7 Ma was also obtained by LA-ICP-MS zircon U-Pb technique for rhyolite from Jiangzhen Formation, which is late volcanism in Huaining basin. Based on a comparison with other volcanic basins in the Middle-lower Yangtze region, the authors found that the ages of volcanism in Huaining basin are similar to those of such other volcanic basins in the Middle -lower Yangtze region as Luzong basin and Ningwu basin; nevertheless, the end of volcanism in Huaining basin occurred about 6 Ma later than other volcanic basins. The volcanic rocks in Huaining basin have wider variation range and lower ε Nd(t) values than other shoshonite volcanic basins in the Middle-lower Yangtze region, which may be related to the fact that their tectonic setting was near the Dabie orogen, and hence more crust materials were added to the magma. The proto magma of Huaining volcanic basin mainly came from partial melting of the enriched mande, with different degrees of mixture of lower crust materials during the magmatic evolution.

The Neoproterozoic mafic-ultramafic rocks are widely developed in the Fanjingshan region, southwestern margin of the Jiangnan orogen, the rocks are all belong to tholeiitic series and including pillow lava, mafic-ultramafic sills and hypabyssal intrusive, gabbro. The pillow lavas are characterized by rich in strong incompatible elements such as Rb, Ba, Th and U as well as light rare earth elements (LREE), deplete in high-field-strong-elements (HFSE) such as Nb and Ta, and lower εNd(t) values, different to the basalt formed in ocean ridge setting obviously, guess them formed by partial melting of enriched mantle in the tectonic setting of small ocean basin back arc-island arc related with subduction. The mafic-ultramafic sills are mainly composed of diabase and calc-pyroxene peridotite, there are abundant original calcite crystals in the ultramafic sills, indicating a extrusion (rift) tectonic setting. The gabbro may be a latest magmatic rock in the region, their SHRIMP zircon U-Pb age is 821 ±4Ma. The degrees of deplete in high-field-strongelements and rich in light rare earth elements are depressing from pillow lava, mafic-ultramafic sills to gabbro, and the ε Nd(t) values from negative change to positive, show that the contribution of depleted mantle increase with time. Authors deduce that the gradation of Neoproterozoic magmatism in the Fanjingshan region is approximately as follow: pillow lava (∼840Ma)→S-type granite (∼838Ma) →calc-ultramafic sills→mafic sills→gabbro, the tectonic setting changed from subduction-collision to extended-rifting.

The Luzong basin locates at northeastern margin of the Yangtze craton and the foreland area of the Dabie-Sulu orogen, and convergent section of the Tanlu fault and the Yangtze River fault, is a typical tectonic place. The volcanic-subvolcanic rocks in the basin are characterized by high-K and rich in alkali, belong to typical shoshonite series. In geochemistry, these rocks exhibit obvious depletion in high-field-strong-elements (HFSE) such as Nb and Ta, enriched in strong incompatible elements such as Rb, Th, U and K as well as light rare earth elements (LREE). Nd and Sr isotope compositions of the rocks indicate that their parental magma mainly formed by partial melting of the enriched subcontinental lithospheric mantle. The volcanic rocks developed in the Luzong basin can divided into Longmenyuan Formation, Zhuanqiao Formation, Shuangmiao Formation and Fushan Formation respectively from early to late, with clear extrusive gap among different Formations. In this work, we used zircon SHRIMP U-Pb technique accurately dating samples from four Formations in the Luzong basin, yield emplacement ages of 131±1 Ma, 133±1 Ma, 130±1Ma and 127±1 Ma respectively, show that whole volcanic rocks in the Luzong basin formed in a very short period of time (≤6 Ma). These data, combined with the time of whole volcanism in the Middle and Lower Yangtze River reaches, predicate an "sudden" volcanic event, imply delamination as the main model for lithospheric thinning of the region (and the whole lower Yangtze region).

The Neoproterozoic mafic-ultramafic rocks are widely developed in the Fanjingshan region, southwestern margin of the Jiangnan orogen, the rocks are all belong to tholeiitic series and including pillow lava, mafic-ultramafic sills and hypabyssal intrusive, gabbro. The pillow lavas are characterized by rich in strong incompatible elements such as Rb, Ba, Th and U as well as light rare earth elements (LREE), deplete in high-field-strong-elements (HFSE) such as Nb and Ta, and lower epsilon(Nd)(t) values, different to the basalt formed in ocean ridge setting obviously, guess them formed by partial melting of enriched mantle in the tectonic setting of small ocean basin back arc-island arc related with subduction. The mafic-ultramafic sills are mainly composed of diabase and calc-pyroxene peridotite, there are abundant original calcite crystals in the ultramafic sills, indicating a extrusion (rift) tectonic setting. The gabbro may be a latest magmatic rock in the region, their SHRIMP zircon U-Pb age is 821 +/- 4Ma. The degrees of deplete in high-field-strong-elements and rich in light rare earth elements are depressing from pillow lava, mafic-ultramafic sills to gabbro, and the epsilon(Nd)(t) values from negative change to positive, show that the contribution of depleted mantle increase with time. Authors deduce that the gradation of Neoproterozoic magmatism in the Fanjingshan region is approximately as follow: pillow lava (similar to 840Ma)-> S-type granite (similar to 838Ma) -> calc-ultramafic sills -> mafic sills -> gabbro, the tectonic setting changed from subduction-collision to extended-rifting.

The Suizhou-Zaoyang area (northern margin of the Yangtze craton),where is the least affected area of the whole Qinling-Tongbaishan-Dabieshan-Sulu orogen and their foreland by the deep subduction of the Yangtze Craton beneath to the North China Craton and HP-UHP metamorphism during Triassic,relative well preserved Precambrian basement of the northern Yangtze Craton.These low-rank metamorphosed Precambrian rocks not only provide an ideal opportunity to study the palaeo-tectonic setting of the northern Yangtze Craton and nature of the lithosphere,but also are rare-references for resuming protolithes of the metamorphic complex in the orogen and examining the element mobility during HP-UHP metamorphism.The Precambrian rocks exposed here include Neoproterozoic volcanic-sedimentary rock series (Suizhou Group) and voluminous Neoproterozoic ultramafic-mafic sill swarm.The Suizhou Group is composed of meta-acidic volcanic rocks,meta-basic volcanic rocks,and meta-sedimentary rocks.The ultramafic-mafic sill swarm is composed predominantly of two-pyroxene troctolites,with minor gabbronorites and pyroxenites.In this work,we used zircon SHRIMP U-Pb technique accurately dating the rhyodacitic tuff and meta-trachyandesite of the Suizhou Group,as well as two-pyroxene troctolitic sill swarm,yielding an emplacement ages of 763±7Ma,741±7Ma and 632±6Ma,respectively.The two former ages are similar to the emplacement ages of protolithes of the HP-UHP metamorphic rocks outcropped in the orogen,but it is still not sure whether there are any emplacement ages of protolith of the eclogite in the orogen are similar to the emplacement ages of the troctolitic sill swarm (632±6Ma).Geochemically,the acidic volcanic rocks exhibit obvious depletion in Sr and high field strong elements (HFSEs) such as Nb and Ta,enrichment in strong incompatible elements such as Rb,Ba,Th,U and K as well as light rare earth elements (LREEs).This type of rocks also show characteristics of strong enrichment in LREE over the HREE ((La/Yb)N=10.44),and weak negative Eu anomalies (δEu=0.75),similar to the biotite plagiogneisses widely distributed in the Dabie-Sulu orogen and acidic end-member of bimodal volcanic rocks developed in rift setting.The meta-trachyandesite of the Suizhou Group show no fractionation between LREE and HREE,no negative HFSEs anomalies such as Nb and Ta,similar geochemically to most eclogites in the orogen.The troctolitic sill swarm is characterized by high Al2O3 and MgO contents,low TiO2 and alkaline contents,strong enrichment of LREE over HREE ((La/Yb)N=5.49),particular for strong positive Ba,Sr and Eu anomalies (δEu=1.22),indicating plagioclase crystallization/accumulation.No HFSEs such as Nb,Ta,U,Th,Zr and Hf anomalies for the troctolitic sill swarm show little contamination of crustal material during evolution of the magmas,and that the parent magma could be derived from partial melting of an enriched subcontinental lithospheric mantle.

The Chuzhou basin,one of the several late Mesozoic volcanic basins developed in the middle and lower reaches of the Yangtze River,is the only basin directly superimposed upon the Dabie orogenic belt,with relatively basement composed of Neoproterozoic-lower Paleozoic strata.The volcanic rocks in the Chuzhou basin are mainly intermediate-acidic trachyandesite and trachydacite,which belong to high-K cal-alkaline series and greatly differ from most late Mesozoic volcanic basins in the middle and lower reaches of the Yangtze River such as Ningwu basin,Luzong basin,Lishui basin and Huaining basin which belong to the shoshonitic series in geochemistry.In this study,the authors used zircon SHRIMP U-Pb technique to perform accurate dating of a trachyandesitic sample from the Huangshiba Formation in the Chuzhou basin,which yielded an emplacement age of 128±1 Ma.This age is similar to the emplacement ages of volcanic/sub-volcanic rocks in other late Mesozoic volcanic basins,suggesting that the whole volcanism in the middle and lower reaches of the Yangtze River were developed in a very short period of time.The volcanic rocks in the Chuzhou basin have remarkably lower eNd(t)values than those in other volcanic basins but are similar to those of the late Mesozoic granitoid intrusive bodies in the Dabie orogen,indicating that their parent magma might have been mainly derived from partial melting of old lower crust.

大别山造山带内广泛发育晚中生代的花岗岩类侵入体,天柱山岩体是其中的一个典型代表,位于分隔南大别超高压变质带与北大别杂岩之间的五河-水吼断裂带附近。该岩体是个由多期次侵位构成的复式岩体,自早到晚依次为闪长岩→石英正长岩/花岗闪长岩→碱长花岗岩。整个杂岩体属高钾钙碱性系列,但碱长花岗岩的地球化学性质与构成杂岩体的其他类型岩石之间存在着显著的差异,拥有A型花岗岩的很多地球化学特征,但大量存在的包裹体（围岩俘虏体及暗色细粒包体）和低的Zr饱和温度又明显不同于典型的A型花岗岩,推测属高度演化的I型花岗岩。地球化学特征显示天柱山花岗岩类的成因与整个大别山造山带内晚中生代的花岗岩类似,来自古老下地壳物质的部分熔融,形成于晚中生代整个中国东部岩石圈减薄的构造背景下。测得该复式岩体中花岗闪长岩和碱长花岗岩的LA-ICP-MS锆石U-Pb年龄分别为127.8±0.7 Ma和127.7±1.0 Ma,两者的侵位年龄几乎完全一致,岩相特征也显示,碱长花岗质岩浆侵位时,花岗闪长岩尚未完全固结。

There are a series of Neoproterozoic granitoids developed in eastern segment of the Jiangnan orogen, LA-ICP-MS zircon U-Pb ages and whole-rock geochemical compositions were determined for those main granitoid intrusions, including Xucun body, Shexian body, Xiuning body, Lingshan body, Lianhuashan body and Shi'ershan body. The granitoid intrusions in the region can be classified into S-type and A-type in petrology and geochemistry, and the former belong to synorogenic magmatic rocks and are mainly granodioritic in component, while the latter belong to late-orogenic magmatic rocks and are granitic in component. The S-type granodioritic magma was generated by partial melting of immature metamorphic sedimentary-volcanic rock, series under dynamic background of collision and crust thicken. But from synorogenic to late-orogenic stages, along with the stress changed fron extrusion to extension, the A-type granites formed include obvious mantle-derived matter. The two types intrusions distributed regularly in space, show obvious southward (ocean side) migration with time. The synorogenic S-type granodioritic intrusions are all located, at the north of the South Anhui suture belt (and inside the suture zone), the Xucun intrusion of S-type granodiorite, situated at the most north part, has the earliest emplacement age of 850 ± 10Ma; Shexian intrusion of S-type granodiorite, which located inside the Anhui suture zone and has the feature of syntectonic, has the emplacement age of 838 ± 11Ma; and also located, inside the suture zone but has the feature of late tectonic, the Xiuning intrusion of S-type granodiorite has the intrusion age of 826 ± 6Ma. Whereas late-orogenic A-type granites are all located at the south of the suture zone, emplacement ages for Lingshan and Lianhuashan A-type granites are 823 ± 18Ma and 814 ± 26 respectively, the two ages are consistent each other considering the errors, and can represent as the time of late-orogenic stage magmatism. The Shi'ershan granite-porphyry formed in post-orogenic rift setting has the emplacement age of 785 ± 11Ma. We consider that the Jiangnan orogen formed in Neoproterozoic era, with characteristics of poly-island arcs amalgalation and poly-sutures. The closing times for different sutures are difference, the earliest closing suture may be the Northeast Jiangxi suture, followed by the Jiangshan-Shaoxin suture, the South Anhui suture was final closed. The arc-type volcanic rocks related with different suture are difference in geochemistry, the two former were developed on oceanic crust background, while the latter was formed on immature continental crust. The Jiangnan orogen had been destroyed by post-orogenic rifting before long it formed, just up to the telophase of Early Paleozoic, the rift between the Yangtze and Cathaysia cratons bad final been closed and formed unionized continent of South China.