1970-2007年西藏念青唐古拉峰南、北坡冰川显著退缩

1999年和2007年夏季,利用GPS技术先后对念青唐古拉峰(念峰)南、北坡的5条冰川末端位置进行了实地测量.结果表明:同1970年比较发现,过去近40 a来5条冰川退缩显著,1970-2007年间念峰北坡的拉弄和扎当冰川与南坡的爬努冰川末端平均退缩速率均接近10.0 m.a-1;西布冰川在1970-1999年间达到38.9 m.a-1,而爬努冰川流域海拔较高的小冰川5O270C0049退缩幅度较小,为4.8 m.a-1.2007年野外观测发现,爬努冰川1970年代的积累区有冰面河形成.念峰周围的冰川变化,不仅仅是末端的显著退缩,而且消融区面积也在扩大.     

宁镇矿集区安基山花岗闪长斑岩和韦岗花岗闪长岩的锆石U- Pb年龄、Hf同位素特征及其地质意义

宁镇矿集区位于长江中下游成矿带东部,发育了大量与Cu、Fe矿产有关的中酸性侵入岩,如区内安基山岩体和韦岗岩体分别与安基山铜矿及伏牛山铜矿、韦岗铁矿等Cu、Fe矿床成矿关系密切。尽管前人在宁镇矿集区开展了大量的岩石学工作,但是对这些花岗质岩石源区特征方面的研究却略显薄弱。本文对该矿集区内的安基山岩体和韦岗岩体开展了详细的LA- ICP- MS 锆石U- Pb测年和锆石Hf同位素研究,进而确定成岩年龄、探讨岩浆源区性质及与成矿作用的关系。锆石U- Pb定年结果显示区内安基山花岗闪长斑岩和韦岗花岗闪长岩成岩年龄分别为108.9~110.9 Ma和107.3~109.6 Ma,宁镇矿集区晚中生代岩浆岩的成岩时代在110~100 Ma之间,明显晚于长江中下游其他矿集区成岩时代范围近20 Ma。两个岩体的锆石Hf同位素研究显示,韦岗花岗闪长岩的εHf(t)值为-47.4~-16.9,平均为-24.9,二阶段Hf模式年龄(TDM2)为2.24~4.14 Ga,平均为2.73 Ga,可能是中太古代至古元古代下地壳部分熔融形成的;而安基山花岗闪长斑岩的εHf(t)值为-16.8~-8.9,平均为-12.4,二阶段Hf模式年龄(TDM2)为1.74~2.23 Ga,平均为1.96 Ga,可能是富集岩石圈地幔物质与下地壳物质混合的产物。本文研究结果结合前人研究显示,矽卡岩型Fe矿床有关的岩体相比于矽卡岩型Cu矿床成矿岩体含有更多的地壳物质;岩浆源区壳、幔物质含量比例可能是控制长江中下游成矿带Cu、 Fe成矿作用的重要因素。     

Serpentinized Peridotites at the North Part of the Wadi Allaqi District (Egypt): Implications for the Tectono-Magmatic Evolution of Fore-arc Crust

The Neoproterozoic Allaqi-Heiani suture （800-700 Ma） in the south Eastern Desert of Egypt is the northernmost linear ophiolitic belt that defines an arc-arc suture in the Arabian- Nubian shield （ANS）. The Neoproterozoic serpentinized peridotites represent a distinct lithology of dismembered ophiolites along the Allaqi-Heiani suture zone. The alteration of peridotites varies, some contain relicts of primary minerals （Cr-spinel and olivine） and others are extremely altered, especially along thrusts and shear zones, with development of talc, talc-carbonate and quartz-carbonate. The fresh cores of the chromian spinels are rimmed by ferritchromite and Cr- magnetite. The fresh chromian spinels have high Cr# （0.62 to 0.79）, while Mg# shows wider variation （0.35-0.59）. High Cr# in the relict chromian spinels and Fo content in the primary olivines indicate that they are residual peridotites after extensive partial melting. The studied ophiolitic upper mantle peridotites are highly depleted and most probably underwent high degrees of partial melting at a supra-subduction zone setting. They can be produced by up to -20%-22% dynamic melting of a primitive mantle source. The mineralogical and geochemical features of the studied rocks reflect that the mantle peridotites of the north part of the Wadi Allaqi district are similar to the fore-arc peridotites of a supra-subduction zone.     

甘肃白银厂铜多金属矿田折腰山矿床下盘脉状矿体流体包裹体特征及其意义

甘肃白银厂矿田位于祁连山块状硫化物矿床成矿省东部,矿体主要赋存于早-中寒武世石英角斑岩-细碧岩组合中。本文主要对折腰山矿床下盘脉状矿体成矿流体进行研究,分析成矿流体性质及成矿流体来源,探讨其成矿机制。含矿石英中流体包裹体的岩相学和显微测温结果表明,包裹体类型主要有液体包裹体、气体包裹体、纯气体包裹体、含CO2三相包裹体、纯CO2包裹体。第Ⅰ阶段包裹体的均一温度为201~413℃,盐度为1.43%~13.40%;第Ⅱ阶段包裹体的均一温度为217~428℃,盐度为1.91%~11.93%(NaCl,wt)。包裹体成分研究表明,成矿流体气相成分主要为H2O,次为CH4和CO2,阳离子主要为Na+,阴离子主要为Cl-,说明成矿流体为H2O-NaCl-CO2-CH4体系。该矿床下盘脉状矿体的流体为岩浆流体与加热海水的混合流体,引起矿质沉淀的机制为混合作用。     

Inclusions in Aquamarine from the Suprunovskoye Pegmatite Deposit, Russia

Please refer to the attachment(s) for more details.     

藏北索县-巴青地区中侏罗世生物礁古生态学研究

索县、巴青地区均位唐古拉山脉的南侧,属于羌塘地层区,其中,索县的桑卡拉佣组和巴青马如的布曲组中均发育有生物礁。造礁生物主要为六射珊瑚Schizosmilia、层孔虫Parastromatopora以及双壳类Liostrea。在分析造礁生物的个体生态特征基础上,根据研究区造礁生物类型及其组合特征,将生物礁划分为5个造礁群落,即Schizosmilia-Parastromatopora,Parastromatopora,Schizosmilia,Liostrea和Cyanobacteria-Liostrea造礁群落,并阐述了各群落的组成、结构与功能以及生态环境特征。根据群落在纵向上的组合与发育特征,分析了造礁群落的演化与海平面的变化特征,其中,Schizosmilia-Parastromatopora,Parastromatopora和Schizosmilia三个群落构成了索县地区造礁群落的演化序列,Liostrea和Cyanobacteria-Liostrea构成了巴青地区造礁群落的演化序列,造礁群落演化分析表明,群落演化表现为两种形式,第一种形式为群落演替,这种形式主要发育于索县桑卡拉佣组生物礁中;第二种形式为群落取代,这种形式主要发育于巴青布曲组生物礁中。最后,阐述了研究区的生物礁的发育特征与成礁方式,认为研究区主要成礁方式有造架作用、障积作用和黏结-障积作用,其中前两者主要体现于桑卡拉佣组生物礁中,后两种主要见于巴青布曲组生物礁中。     

Seasonal Rainfall Forecasts for the Yangtze River Basin in the Extreme Summer of 2020※

Seasonal forecasts for Yangtze River basin rainfall in June, May–June–July (MJJ), and June–July–August (JJA) 2020 are presented, based on the Met Office GloSea5 system. The three-month forecasts are based on dynamical predictions of an East Asian Summer Monsoon (EASM) index, which is transformed into regional-mean rainfall through linear regression. The June rainfall forecasts for the middle/lower Yangtze River basin are based on linear regression of precipitation. The forecasts verify well in terms of giving strong, consistent predictions of above-average rainfall at lead times of at least three months. However, the Yangtze region was subject to exceptionally heavy rainfall throughout the summer period, leading to observed values that lie outside the 95％ prediction intervals of the three-month forecasts. The forecasts presented here are consistent with other studies of the 2020 EASM rainfall, whereby the enhanced mei-yu front in early summer is skillfully forecast, but the impact of midlatitude drivers enhancing the rainfall in later summer is not captured. This case study demonstrates both the utility of probabilistic seasonal forecasts for the Yangtze region and the potential limitations in anticipating complex extreme events driven by a combination of coincident factors.     

http://www.sciencedirect.com/science/article/pii/S1674987112001533

The collision of a divergent ocean ridge may evolve into two end cases:in the continuity of ocean-floor subduction.or in the detachment of the subducted plate.The northern Patagonia active plate margin has the unique situation that in Cenozoic time it has been subjected to two divergent ridge collisions,each one representing one of the end members.The Neogene Antarctica-Nazca divergent ridge collision evolved as a continuous ocean-floor subduction system,promoting a magmatic hiatus at the arc axis,the obduction of part of the ridge ocean-floor in the fore-arc.and basaltic volcanism in the back-arc.In contrast,the Paleogene Farallon-Aluk divergent ridge collision evolved into a transform margin,with the detachment and sinking of the Aluk plate and the development of a large slab window.As in the previous case,this collision promoted a magmatic hiatus at the arc axis,but the tectono-magmatic scenario changed to postorogenic synextensional volcanism that spread to the former fore-arc（basalt,andesite,rhyolite） and former back-arc（bimodal ignimbrite flare-up,basalt）.Geochemistry of this slab window synextensional volcanism shows more MORB-like basalts towards the former fore-arc,and MORB-OIB-like basalts towards the former back-arc.Instead,an isolated undeformable crustal block in the former back-arc,with an "epeirogenic" response to the slab window and extensional regime,was covered by OIB-type basalts after uplift.Major elements show that slab window basalts reach TiCh values up to 3 wt%,as compared with the top value of 1.5 wt%of arc magmas.Besides,the MgO with respect to（FeO^t + Al₂O₃） ratio helps to distinguish slab window magma changes from the former fore-arc to the former back-arc and also with respect to the "epeirogenic" block.Higher contents of HFS elements such as Nb and Ta also help to distinguish this slab window from arc magmas and also,to distinguish slab window magma changes from the former fore-arc to the former back-arc and "epeirogenic" block settings.The isotope compositions of slab window magmatism show a disparate coeval array from MORB to crustal sources,interpreted as a consequence of the lack of protracted storage and homogenization due to the extensional setting.     

关于推进实施海洋生态化管理的几点思考

2l世纪是海洋的世纪。在开发蓝色国土的热潮中,海洋经济得到了飞速发展。据初步核算,2010年全国海洋生产总值38439亿元,比2010年增长12.8%;全国海洋生产总值占国内生产总值的9.7%。开发海洋在给人类带来巨大经济效益的同时,也产生明显的负面效应,如海洋环境被污染、海洋资源遭到破坏、海洋健康受到严重影响以及海洋生态系统退化加     

规划控地挖潜节地——湖北省咸宁市推进节约集约用地的做法

咸宁市是湖北省的南大门,是一座宜居宜业宜游的魅力之城、活力之城,享有“香城泉都”美誉.地型地貌为“六山一水两分田,一分土地为家园”.全市国土面积9861平方公里,耕地面积301.1万亩,人均耕地1.1亩.近年来,随着省级咸宁发展战略和一元多层次战略的实施,作为湖北省国土资源“三项改革”暨闲置低效用地处置推进工作的示范区,咸宁举全市之力贯彻落实省政府节约集约用地新政策和新措施,有力推进了土地利用方式转变,走出了一条有自身特色的节约集约用地新路径.