Mineralization,Geochemistry and Zircon U‐Pb Ages of the Paodaoling Porphyry Gold Deposit in the Guichi Region,Lower Yangtze Metallogenic Belt,Eastern China

The newly discovered Paodaoling porphyry Au deposit from the Guichi region, Lower Yangtze River Metallogenic Belt(LYRB), contains 35 tons of Au at an average grade of ~1.7 g/t. It is a porphyry ‘Au-only' deposit, as revealed by current exploration in the depths, mostly above-400 m, which is quite uncommon among coeval porphyry mineralization along the LYRB. Additionally, there are also Cu-Au bearing porphyries and barren alkaline granitoids in the Paodaoling district. Zircon LA-ICP-MS U-Pb dating of the Cu-Au-bearing porphyries yield an age of 141–140 Ma, falling within the main magmatic stage of the LYRB, whereas the barren granites give an age of 125–120 Ma, coeval with the regional Atype granites. The Cu-Au-bearing porphyries are LILE-, LREE-enriched and HFSE-depleted, typical of arc magmatic affinities. The barren granites are HFSE-enriched, with lower LREE/HREE ratios and pronounced negative Eu anomalies. The Cu-Au-bearing porphyries in the Paodaoling district have high oxygen fugacities and high water content. Pyrite sulfur isotopes of the Paodaoling gold deposit indicate a magmatic-sedimentary mixed source for the ore-forming fluids. Based on the alteration and poly-metal zonation of the deepest exploration drill hole from the Paodaoling Au deposit, we propose that Cu ore bodies could lie at depth beneath the current Au ore bodies. The magmatism and associated Cu-Au mineralization of the Paodaoling district are likely to have formed in a subduction setting, during slab rollback of the paleo-Pacific plate.     

OCEAN BOTTOM SEISMOMETER AND ONSHOREOFFSHORE SEISMIC EXPERIMENT IN NORTHEASTERN SOUTH CHINA SEA

Three-component Ocean Bottom Seismometers, portable land stations and marine air gun seismic sources were used to carry out an onshore-offshore deep seismic profile in northeastern South China Sea. This profile, orientated in NNW-SSE, was as long as 500 km and perpendicular to the strike of regional tectonics. The offshore data were processed in Taiwan Ocean University using a number of available software and the onshore data were analyzed in South China Sea Institute of Oceanology by new-written programs and public software. Preliminary results show that the seismic data are in good quality and contain rich information of deep structure. Seismic phases, e.g. Pg, PmP and Pn, are identified in the offset range 5～220 km, which will provide an important dataset for the deep crustal structure and oil-gas basin evolution studies of this region.     

Geochemistry of peridotite xenoliths in alkali basalts from Jeju Island, Korea

Abstract   Ultramafic xenoliths in alkali basalts from Jeju Island, Korea, are mostly spinel lherzolites with subordinate amounts of spinel harzburgites and pyroxenites. The compositions of major oxides and compatible to moderately incompatible elements of the Jeju peridotite xenoliths suggest that they are residues after various extents of melting. The estimated degrees of partial melting from compositionally homogeneous and unfractionated mantle to form the residual xenoliths reach 30%. However, their complex patterns of chondrite-normalized rare earth element, from light rare earth element (LREE)-depleted through spoon-shaped to LREE-enriched, reflect an additional process. Metasomatism by a small amount of melt/fluid enriched in LREE followed the former melt removal, which resulted in the enrichment of the incompatible trace elements. Sr and Nd isotopic ratios of the Jeju xenoliths display a wide scatter from depleted mid-oceanic ridge basalt (MORB)-like to near bulk-earth estimates along the MORB–oceanic island basalt (OIB) mantle array. The varieties in modal proportions of minerals, (La/Yb)_N ratio and Sr-Nd isotopes for the xenoliths demonstrate that the lithospheric mantle beneath Jeju Island is heterogeneous. The heterogeneity is a probable result of its long-term growth and enrichment history.     

A PETROGRAPHICAL STUDY OF THE CHINESE AGALMATOLITES

Ⅰ. INTRODUCTION. The most popular Chinese agalmatolites are Shoushanshih (壽山石), Changhuashih (昌化石), Chingtienshih (青田石) and Kwanglushih (廣綠石). They are named after the names of places, as the name Shoushanshih is from     

Underplating of Mesozoic Mantle-derived Magmas in Tongling, Anhui Province: Evidence from Megacrysts and Xenoliths

Lithological observations and mineralogical analyses on pyroxene and hornblende megacrysts and pyroxene and hornblende cumulates in xenoliths in the Mesozoic plutons of the Tongling region, Anhui Province, provide evidence for the magmatic underplating of mantle-derived alkali-olivine basalt at circa 140 Ma. The pyroxene and hornblende megacrysts and cumulates were formed through the AFC process at depths ranging from 27 to 35 km.     

黄河改道与地图断代:中国地图学西传辩证

黄河经常改道,给中国带来肥沃的耕地,也带来灾难。历代黄河河道变迁反映在地图上,可以断定地图的成图年代。先秦至宋代,黄河基本在华北平原用不同河道进入渤海。自1194年开始,黄河夺淮,分两支,北入渤海,南注黄海。1580年治河后,黄河只有南支汇淮河入黄海,到1855年再恢复单支入渤海。黄河4次大改道的历史可以印证地图成图年代。《坤輿万国全图》上的黄河分两支,为1194—1580年状态,不是利玛窦与李之藻时代的黄河,他们应该目击而未更正,证明两者均没有参加《坤輿万国全图》的测绘,地图存在远较二人时代为早。卫匡国的《中国新地图集》,黄河只表示南支入黄海,是1580年以后的材料,比1541年的《广舆图》资料更新。地图制作有勘探、测绘、拼合、制版、印刷、翻译等步骤。严格来说,地图最重要的创作者是勘探测绘者,其他的任务是后勤,翻译重绘更是省事。《中国新地图集》主要制作人不是卫匡国,实为中国历代省、县、乡分工测绘,明代统其成,已用经纬线,球形投影绘制。《坤輿万国全图》则是郑和等率领大航海的经验总结。卫、利、李等人只参与翻译,添加地名和序言。这两份外国保存的中国地图重现中国历史,证明郑和时代的大航海是世界地理大发现的先驱,近代地图学为中国原创,中国地图学西传才更接近史实。     

急性UVB辐射对粉叶马尾藻过氧化损伤和主要抗氧化酶的影响

粉叶马尾藻(Sargassum glaucescens)是台湾地区潮间带的重要大型藻类,其对紫外线增强的生理响应特征尚不清楚。本研究关注粉叶马尾藻在急性紫外线辐射(Ultraviolet radiation B,UVB)下的生理指标变化,探索了粉叶马尾藻在急性UVB辐照下抗氧化系统的瞬时反应过程。结果表明:低强度组[0.5W/(m2·s)]藻体在24h内未出现显著氧化损伤和蛋白质含量变化,但是细胞活力在辐照12h后显著降低,藻体超氧化物歧化酶(SOD)酶活性随辐照时间延长而降低,过氧化氢酶(CAT)酶活性呈现升高后下降的趋势,抗坏血酸过氧化物酶(APX)酶活性没有出现显著降低;高强度组[2W/(m2·s)]藻体在辐照3h后藻体出现明显氧化损伤,6h后细胞活力和蛋白质含量显著降低,藻体SOD酶活性随辐照时间延长而降低,CAT和APX酶活性呈现升高后降低的趋势,辐射12h后即显著降低。低强度UVB辐射对粉叶马尾藻的影响相对较小,表明粉叶马尾藻对UVB辐射具有一定耐受性;而高强度UVB辐射的影响较为显著,意味着UVB辐射的持续增强将超出粉叶马尾藻的耐受限度,进而造成不利影响。本研究结果初步揭示了粉叶马尾藻对于急性UVB辐射的增强的生理响应特征,为进一步研究UVB辐射增强的生态学效应提供参考依据。     

基于重力剖面的长白山天池火山地壳岩浆囊建模

长白山天池火山是中国最具潜在喷发危险的多成因复式火山,在近2000年来,曾经发生过世界上最大规模的喷发。为了进一步研究长白山天池火山的潜在危险,有必要研究火山的岩浆囊位置和分布。为此,在长白山天池火山开展了一条南北方向的重力剖面测量。结合前人工作,如地震勘探P波速度反演和大地电磁测深（MT）电阻率反演,以及地质信息,采用人机交互的形式,建立了一条长约150km的密度模型。从建模结果图中可以发现：（1）长白山天池下方存在地壳岩浆囊;（2）长白山天池北坡地壳存在一个高阻、低密度体,深度在7~15km,距离天池2~10km,可能是富含气体的岩浆囊;（3）在南坡和北坡大约3km深度处普遍存在一个岩浆岩层;（4）在天池下存在一个已经塌陷堵塞的火山颈。     

贵州省遵义市降水中低分子有机酸对自由酸度的贡献

贵州省遵义市是我国酸雨高发地区,研究遵义降水中有机酸对自由酸度的贡献是认识遵义市有机酸地球化学循环和酸雨机制的重要内容。在遵义市中心城区进行了一年的降水采集,并利用离子色谱法和原子吸收光谱法对主要阴离子（包括无机和有机阴离子）和阳离子进行了测定。结果显示,年均pH值为4．11（范围3．12～6．04）,pH〈5．6的样品占93．1％,说明遵义市酸雨污染仍然严重;单因素方差分析显示四季的pH值存在显著差异（P〈0．05）,表明遵义市降水酸化程度具有显著的季节性特征;甲酸和乙酸的雨量加权平均值分别为9．29umol／L和6．47umol／L,检出率分别为98．68％和93．42％,表明有机酸在降水中广泛存在;应用热力学理论计算了有机酸对降水自由酸度的贡献量,发现在pH〈5的遵义降水中甲酸和乙酸对自由酸度的平均贡献量分别为14．79％和3．66％,表明有机酸对降水自由酸度具有重要贡献;对比显示,遵义市的有机酸贡献量低于边远地区,这与遵义市降水的低pH值和高无机酸度有关;四季的有机酸贡献量大小为：春季（31．95％）〉夏季（26．16％）〉冬季（11．17％）〉秋季（8．02％）,可见有机酸对自由酸度的贡献量存在明显的季节性变化。在低酸度和低水温的春季降水中,由于人类活动或有机物质的燃烧所释放的大量有机酸（如汽车尾气的排放、燃煤的燃烧）,促使有机酸对降水自由酸度的贡献量最高;其次是在低酸度和强降雨的夏季;而在低酸度的秋季和冬季,有机酸对酸度的贡献量相对最低。     

Thermal histories of Cretaceous basins in Korea: Implications for response of the East Asian continental margin to subduction of the Paleo‐Pacific Plate

Thermal histories of Cretaceous sedimentary basins in the Korean peninsula have been assessed to understand the response of the East Asian continental margin to subduction of the Paleo‐Pacific (Izanagi) Plate. The Izanagi Plate subducted obliquely beneath the East Asian continent during the Early Cretaceous and orthogonally in the Late Cretaceous. First, the Jinan Basin, a pull‐apart basin, was studied by illite crystallinity and apatite fission‐track analyses. Analytical results indicate that Jinan Basin sediment was heated to a maximum temperature of approximately 287°C by burial. The sediment experienced two cooling episodes during ca 95–80 Ma and after ca 30 Ma, with a quiescent period between them. A similar cooling pattern is recognized in the Gyeongsang Basin, the largest Cretaceous basin in Korea. The Jinan and Gyeongsang Basins were cooled mainly by exhumation between ca 95 and 80 Ma, but the former was exhumed slightly earlier than the latter by transpressional force due to the subduction direction change of the Izanagi Plate. Comparison of thermal history of Korean Cretaceous basins with those of granitoids in northeastern China and the accretionary complexes in southwestern Japan reveals that the Upper Cretaceous regional exhumation of the East Asian continental margin including the Korean peninsula during ca 95–80 Ma was facilitated by the subduction of the Izanagi–Pacific ridge, which migrated northeastwards with time, resulting in the end of regional exhumation at ca 80 Ma in this region.