Rb-Sr chronology and cooling history of the Renjiawan pyroxenite intrusion in North Dabie Terrane

A group of Rb-Sr ages, i.e. plagioclase-whole rock (WR) isochron age of (205 ± 7) Ma, hornblende-WR isochron age of (164 ± 10) Ma and biotite-WR isochron age of (123.4 ± 1.2) Ma, for one pyroxenite sample from Renjiawan in North Dabie Terrane (NDT) are reported. According to the closure temperature of 600℃ for plageoclase and 300℃ for biotite, the Renjiawan pyroxenite should intrude into the NDT before 205 Ma, and the younger Rb-Sr ages may reflect the cooling history of the intrusion or reset by the very strong Cretaceous thermal event in NDT.     

Zircon U-Pb age of the Shacun gabbro body, Yuexi, Dabie orogen and its geological implications

The single grain zircon U-Pb age of the Shacun mafic-ultramafic intrusion, Yuexi, North Dabie is (128.1±2.0) Ma. This date indicates that the intrusion was implaced at Yanshanian when most Mesozoic granitoids were intruded. It was not the syn-collisional intrusion related to the subduction of the Yangtze Block and ultrahigh-pressure metamorphism at Indosinian.     

Rutile U-Pb age for the ultrahigh pressure eclogite from the Dabie Mountains,central China: Evidence for rapid cooling

The U-Pb isotope compositions of rutile, omphacite and garnet in the eclogite from the Jinheqiao area in the Southern Dabie ultrahigh-pressure metamorphic zone were analyzed. The consistent high precision U-Pb age (218 ± 1.2) Ma of rutile in eclogite from the Dabie Mountains was obtained by two ways of isochron and common Pb correction based on the composition of omphacite. This proves that the omphacite in eclogite has a U/Pb ratio (m = 2.8) low enough to be used for common Pb correction in the analyses of rutile. Under the rapid cooling condition (40℃/Ma) the closure temperature for U-Pb diffusion in rutile is about 470℃. Thus, this U-Pb age of rutile proves that 218 Ma should be the cooling age of eclogite at 470℃ instead of the peak metamorphic age.     

Isotopic composition of helium in eclogite from the Dabie Mountains, central China and its geological significance

Isotopic geochemical characteristics of helium in garnet and omphacite of eclogite in the Dabie Mountains are discussed. Concentrations of³He and⁴He in garnet and omphacite are 3.9 × 10⁻¹⁴–24.0 × 10⁻¹⁴ and 0.48 × 10⁻⁷–9.42 × 10⁻⁷cm¹³.g⁻¹, respectively. Values of³He/⁴He have a range of (1.19–4.63) × 10⁻⁷. Helium In the eclogite is derived from both mantle and crust. Isotopic geochemical data of helium indicate that eclogite in the Dabie Mountains might be formed in depleted mantle and the age of the cologite would be Indo-China epoch.     

Isotope composition of helium in eclogite from the Dabie Mountains, central China and its geological significance

Isotopic geochemical characteristics of helium in garnet and omphacite of eclogite in the Dabie Mountains are discussed. Concentrations of 3He and 4He in garnet and omphacite are 3.9×10 -14- 24.0×10 -14 and 0.48×10 -7-9.42×10 -7cm+3·g -1, respectively. Values of 3He/ 4He have a range of (1.19-4.63)×10 -7. Helium in the eclogite is derived from both mantle and crust. Isotopic geochemical data of helium indicate that eclogite in the Dabie Mountains might be formed in depleted mantle and the age of the cologite would be Indo-China epoch.     

SHRIMP dating of zircons from the Caledonian Xiongdian eclogite, western Dabie Mountains, China

This note reports the SHRIMP U-Pb data of zircons from the Caledonian Xiongdian eclogite, western Dabie Mountains. Zircons from the rock occur mainly in garnet and other metamorphic minerals with sharp boundaries and exhibit textures growing under metamorphic conditions. Analyses of 7 grains give ²⁰⁶Pb/²³⁸U ages ranging from 335 to 424 Ma, showing a certain degree of radiogenic lead loss. This suggests a minimum age of (424±5) Ma for the metamorphic zircons, as well as the high-pressure metamorphic event. The outer peripheral zone of a zircon gives ²⁰⁶Pb/²³⁸U age of about 300 Ma. Combined with Sm-Nd, ⁴⁰Ar-³⁹Ar, U-Pb and ²⁰⁷Pb/²⁰⁶Pb ages, the peak metamorphism of the Xiongdian eclogite is documented between 424—480 Ma.     

The white schist assemblage in the kyanite quartzite from the ultrahigh-pressure metamorphic belt, eastern Dabie Mountains

The kyanite quartzite from the ultrahigh-pressure metamorphic belt in the eastern Dabie Mountains is composed mainly of quartz, kyanite, talc and epidote, which contains a typical mineral assemblage of white schist. It suffered an eclogite facies metamorphism of P =(2 4±0 3) GPa and T =630℃ together with coexisting eclogite. The protolith may be an aplite replaced by high-pressure fluid of eclogite facies.     

Carbon isotope anomaly in marbles associated with eclogites from the Dabie Mountains

This is a report of carbon isotope anomaly in marbles associated with the UHP eclogites from the Dabie Mountains. The results place constraints on the degree of crust-mantle interaction during the UHP metamorphism.     

The evidence of Sm-Nd isochron age for the early Paleozoic ophiolite in Mangya area, Altun Mountains

The REE patterns of the basic volcanic rocks in Mangya area, Altun, are slight rich in LREE with (La/Ya)-N=1.69-3.20, (La/Sm)-N=1.37-1.87, other trace element ratios of the rocks are Th/Ta≈1 (for a few samples greater than 1.5), Nb/Y=0.34-0.62, Ti/Y=310-443 (on the average: 381), Ti/V=37-62, Zr/Nb=9.4-12.4, Sr/Rb=12-80 (on the average: 37), and Nb/Th=7.7-16.8. These features are similar to that of E-MORE or OIB. The ε Nd(t) value, being 3.95- 4.12, shows that the source of the volcanic rocks is derived from depleted asthenosphere mantle mixed with materials from enriched mantle. These, together with the information of geological setting and rock assemblages, indicate that the basic volcanic rocks are of ophiolite. The Sm-Nd isotope ages for the eight basic volcanic rock samples construct a straight line with good correlation, and the calculated isochron age is (481.3±53) Ma. Besides, the eight calculated ε Nd(t) and model ages are close to each other, which suggests that they are homologous, so the isochron is not a mixed line. In the meantime, the isochron age ((481.3±53) Ma) is lower than the model ages (T DM=1 004-1 534 Ma) of the samples, suggeting that the isochron age represents the formation age of the basic volcanic rocks and the ophiolite belt in Mangya area, Altun is formed in the early Paleozoic (Cambrian-Ordovician). In spite of the greater uncertainty of the age, it is still reliable because it is consistent with the age constrained by the regional strata.     

The discovery of eclogite dikes in low-greenschist facies volcaniclastic rocks of the Dabie Mountains

Conclusions  

皖西大别山区土壤侵蚀空间分布特征及与地形的关系

基于修正的通用土壤流失方程和GIS空间分析方法,定量分析了皖西大别山区土壤侵蚀空间分布特征,讨论了侵蚀强度与海拔、坡度、坡向等因子的关系.基于信息熵模型评价地形因子与土壤侵蚀强度的空间相关性结果表明:(1)皖西大别山区2010年土壤侵蚀总量为1844.30×10~4t,平均侵蚀模数为1415.05t/km~2·a.区域以微度和轻度侵蚀为主,分别占总面积的52.95%和31.99%,侵蚀强度由东南至西北逐渐加剧.(2)坡度和海拔主导着区域内土壤侵蚀强度的空间分布.随着坡度和海拔增加,侵蚀强度不断加剧,强度侵蚀的面积比例增加,微度侵蚀的面积减少;在坡度15-25°区域、海拔200-500m区域的土壤侵蚀总量最大.坡向对土壤侵蚀强度的影响较小,土壤侵蚀强度在东南坡向较其它坡向略强.(3)地形因子与土壤侵蚀强度的空间相关性强弱为:坡度海拔坡向.坡度是安徽省大别山区土壤侵蚀强度的主导因子.     

Quartz and clinoenstatite exsolutions in clinopyroxene of garnet-pyroxenolite from the North Dabie Mountains, eastern China

The exsolution lamellae of quartz and clinoen-statite are idenfied in diopside of garnet-pyroxenolite from the North Dabie Mountain by transmission electron microscopy, which is interpreted that the lamellae are originally exsolved from a former ultra-high-pressure clinopyroxene due to decreasing of pressure. Study of petrography shows that there is compositional zoning hi the diopside itself. It is implied that the garnet-pyroxenolite had undergone intensive high-temperature granulite fades and high-amphibolitic fades retrogressive metamorphism, while the peridotite (the garnet-pyroxenolite's host rock) emplaced the crust     

大别山区产葛根黄酮对CCl4诱导的小鼠化学性肝损伤保护作用

研究大别山区葛根总黄酮（TPF）对CCl4诱导小鼠化学性肝损伤的保护作用及可能的作用机制。采用1次性腹腔注射（ip）0．1％CCl4花生油溶液（10ml／kg）建立小鼠化学性肝损伤模型。TPF连续灌胃（ig）14d后摘眼球取血,分离血清,测定血清中丙氨酸氨基转移酶（ALT）和天门冬氨酸氨基转移酶（AST）活性;剖腹取肝,制备10％肝匀浆,测定肝组织中超氧化物歧化酶（SOD）、丙二醛（MDA）、干扰素-γ（IFN-γ）、肿瘤坏死因子-α（TNF-α）活性;进行肝组织病理切片,观察肝组织病理学变化。结果显示TPF能降低CCl4诱导的化学性肝损伤小鼠血清中ALT、AST和肝匀浆中MDA、IFI-γ、TNF-α的活性及增强肝匀浆中SOD的活力。其作用机制可能与抗氧化和降低肝组织中IFN-γ、TNF-α水平有关。     

《皖西日报》和《大别山晨刊》的祈使句标题比较研究

《皖西日报》和《大别山晨刊》,作为六安市的党报和都市报,在角色定位、功能类型、媒介立场等方面具有不同特征,这些不同反映在新闻语篇的话语表达中。选取《皖西日报》和《大别山晨刊》的祈使句标题作为研究对象,通过定量比较,考察两种报纸祈使句标题运用的共同和不同特点,分析两种报纸角色定位的不同,探讨其中所隐含的媒介宗旨和立场的差异。     

皖西大别山区野生攀援观赏植物资源与应用研究

通过对皖西大别山区野生攀援观赏植物资源的调查研究,本区有野生攀援植物157种具有较高观赏价值。根据其攀援特性分为缠绕类75种、吸附类17种、卷须类27种、蔓生类38种。探讨了其在园林绿化中的应用形式,对本区野生攀援观赏植物进行了总体评价,并对其开发利用提出了建议。     

U-Pb zircon age of the foliated garnet-bearing granites in western Dabie Mountains, Central China

U-Pb zircon dating on two foliated garnet-bearing granite samples in the western Dabie ultra-high-pressure (UHP) metamorphic unit yields concordant ages of (234±4) Ma and (227±5) Ma, respectively. These ages, following the UHP peak metamorphism, represent the magma emplacement ages for the foliated garnet-bearing granites. This, for the first time, shows that there are the Triassic granites in the Dabie Mountains. The foliated garnet-bearing granites resemble A-type granite in geochemical characteristics, indicating that they were formed in extensional geodynamic setting. The magma formation reflects a reheating event in the Dabie orogenic belt and it enhances the transfer of tectonic regime from collision into extension and promotes the rapid exhumation into lower crust for the UHP metamorphic rocks.