秘鲁南部阿雷基帕段海岸岩基带找矿方向探讨

通过详细的岩相学和锆石U-Pb年龄的研究,秘鲁海岸岩基带阿雷基帕段的填图工作得到了补充,该岩基带岩浆活动可分为7个阶段和4个旋回,各阶段都显示出不同的岩浆容量,其地貌主要表现为岩基和岩脉。旋回Ⅰ和旋回Ⅱ代表侏罗纪岩浆活动阶段（201~145Ma）,岩浆分异为辉长岩到花岗岩;旋回Ⅲ和旋回Ⅳ代表白垩纪岩浆,岩浆分异为英云闪长岩-二长花岗岩、闪长岩与花岗闪长岩及英云闪长岩-花岗闪长岩。对角闪石和黑云母矿物晶体的数量关系研究表明,旋回Ⅰ的侵入岩有大量辉石和角闪石结晶,并伴随金-铁成矿作用;旋回Ⅱ有大量的群集角闪石晶体和呈定向排列或群集的六边形黑云母,且伴随铜-金-铁成矿作用;旋回Ⅲ侵入岩内发育角闪石和黑云母,伴随着金-铜和铁成矿作用;旋回Ⅳ发育大量角闪石和六边形黑云母,岩石更偏长英质,并伴随铜-锌-金-银-铁和铜-金-钼成矿作用。     

南极大型动物粪土层和蛋卵中有机氯污染物分布特征及生态学意义

新近从南极菲尔徳斯半岛和阿德雷岛的海鸟和海豹栖息地粪土层中检出持久性有机氯污染物(POPs)总含量范围: 多氯联苯(PCBs)为0.21~3.85 ng/g; 有机氯农药滴滴涕(ΣDDT)为0.09~2.01ng/g; 六六六(ΣHCH)为0.06~0.76 ng/g, 并以七氯、六氯联苯、P, P-DDE和α-HCH化合物为主体; 在贼鸥和巨海燕、企鹅蛋卵中检出POPs含量各为12.5~294.2和2.0~10.2 ng/g (湿重); 积蓄形式以PCB180, PCB153, P, P’-DDE和HCB和P, P’-DDE为主. 研究表明, 栖息地粪土层POPs含量变化与海鸟不同种群食性以及营巢占域的不同而相异; 对不同种类海鸟卵样的POPs数据进行统计分析, 结果显示不同鸟种POPs积累水平的差异取决于不同鸟种的生态习性, 如活动范围、迁徒距离、觅食习性以及巢址选择等, 最重要是海鸟生态食物链中的位置, 其食谱的宽窄, 同样表明海鸟体内POPs积累通过食物链逐渐加强的结果. 其次还对阿德雷岛地区AD1, AD2短柱粪土地层进行²¹⁰Pb测年, 并进行POPs积累率及分子地层学记录的初步研究.     

Petrology of Submarine Lavas from Kilauea's Puna Ridge, Hawaii

We have studied 30 quenched tholeiitic lava flows recoveredby 20 dredge hauls and one submersible dive along Puna Ridge,the submarine part of the East Rift Zone of Kilauea Volcano,Hawaii Glass grains from numerous additional flows were recoveredin turbidite sands cored in the Hawaiian Trough. These quenchedlavas document variable primary magma compositions; olivineand multiphase crystallization and fractionation; degassing;wall-rock stoping and assimilation; mixing in the crustal reservoirand the rift zone; entrainment of olivine xenocrysts from ahot, ductile, olivine cumulate body; and disruption of gabbrowallrocks in the rift zone. Glass grains in turbidite sands contain up to 15•0wt% MgO,in contrast to < 7•0wt% MgO for the sampled glass rindson lavas. The most forsteritic olivine phenocryst (F0₉₀₇) isin equilibrium with primary Kilauea liquid containing an average16•5 wt% MgO, but ranging from 13•4 to 18•4%.Lavas and glass grains have more restricted P₂O₅/K₂O and TiO₂/K₂Othan glass inclusions in olivine, because more diverse liquidstrapped as glass inclusions are mixed and homogenized beforeeruption. Variable trace element compositions in glass grainsand whole rocks indicate that the primary liquids form by partialmelting of mantle sources retaining clinopyroxene and garnet. Orthopyroxene xenocrysts formed at moderate pressures provideevidence for a sub-crustal staging zone. Chromite and olivinecrystallize in the crustal magma reservoir as the liquid coolsfrom an average 1346C to 1170C. Low viscosities of the primaryliquids (04 Pas) facilitate olivine settling, and the crystallizedolivine forms an olivine cumulate body at the base of the reservoir.Olivine is deformed as the hot ductile dunite body flows downand away from the summit. This flow drives instability of theHilina landslide on Kilauea. Dikes intrude the dunite, and magmaflowing through the dikes disaggregates and entrains olivinexenocrysts in Puna Ridge magmas. Primary liquids pond at or near the base of Kilauea's crustalreservoir because they are denser than more fractionated liquidsthat occupy the upper parts of the reservoir. The sulfur andwater contents of glass rinds indicate that fractionated liquidsnear the top of the reservoir degas at low pressure, a processthat increases their density and causes them to sink to levelswhere they mix with resident undegassed, near-primary liquid.The fractionated liquids near the top of the magma reservoiracquire excess Cl, owing to assimilation of hydrothermally alteredroofrocks. Magma flowing into the rift zone encounters and mixes with low-temperature,multiphase-fractionated melt. The mixed magmas typically containrare orthopyroxene, plagioclase as sodic as andesine, olivineas fayalitic as F0₇₅ and Fe-rich augite derived from the fractionatedmagma. Magma flowing through dikes also dislodged fragmentsof gabbroic wallrocks that occur as xenoliths. The interrelations in the Kilauean submarine lavas between hostglass and glass inclusion compositions, volatile contents andmineral chemistry reveal an extraordinarily complex sequenceof petrogenetic processes and events that are difficult or impossibleto determine in subaerial Kilauea lavas because of crystallization,reequilibration and degassing during or after their eruption. KEY WORDS: submarine lavas; petrology; Kilauea; Hawaii; magma mixing ^*Corresponding authorPresent address: Rosentiel School of Marine and Atmospheric Science, Division of Marine Geology and Geophysics, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149-1098, USA     

Identification of the natural product 2,3,4,5-tetrabromo-1-methylpyrrole in Pacific biota, passive samplers and seagrass from Queensland, Australia

Halogenated natural products (HNPs) are frequently detected in marine organisms. High HNP concentrations have previously been found in marine mammals from the Great Barrier Reef, Australia, including in the blubber of herbivorous dugongs (Dugong dugon). To identify the source of HNPs we initially focused on the analysis of Australian seagrass (Halophila ovalis) which serves as the principal food source for dugongs. GC/MS analysis of the seagrass indicated the presence of several organobromine compounds. One compound was identified as 2,3,4,5-tetrabromo-1-methylpyrrole (TBMP) by synthesis. Subsequent analysis of semipermeable membrane devices demonstrated that the photo-sensitive TBMP is widespread in the Great Barrier Reef (Queensland, Australia). The detection of larger TBMP concentrations in fish fillets from Chile and traces in mussels from New Zealand indicated that this potential HNP may be distributed throughout the Southern Pacific Ocean.     

Response of the upper ocean to tropical cyclone in the Northwest Pacific observed by gliders during fall 2018

The evolution of thermohaline structure at the upper ocean during three tropical cyclones(TCs) in the Northwest Pacific was studied in this study based on successive observation by two new-style underwater gliders during fall 2018. These remote-controllable gliders with CTD sensor enabled us to explore high frequency responses of temperature, salinity, mixed and barrier layers in the upper ocean to severe TCs in this area. Results showed that three significant cooling-to-warming and stratification destructing-to-reconstructing processes at the mixed layer occurred during the lives of three TCs. The maximal cooling of SST all reached ≥0.5℃ although TCs with different intensities had different minimal distances to the observed area. Under potential impacts of solar radiation, tide and inertial motions, the mixed layer depth possessed significant high-frequency fluctuations during TC periods.In addition, barrier layers appeared and vanished quickly during TCs, accompanied with varied temperature inversion processes.     

Rheologic properties of the lithosphere and applications to passive continental margins

Thermal and petrologic models of the crust and upper mantle are used for calculating effective viscosities on the basis of constant creep rates. Viscosity—depth models together with pressure—depth models are calculated for continental and oceanic blocks facing each other at continental margins. It is found from these “static models” that the overburden pressure in the lower crust and uppermost mantle causes a stress which is directed from the ocean to the continent. The generally low viscosity of 10²⁰–10²³ poise in this region should permit a creep process which could finally lead to a “silent” subduction. In the upper crust static stresses act in the opposite direction, i.e. from the continent to the ocean, favouring tension which could produce normal faulting in the continent. Differences between observations and the results obtained from the static models are attributed to dynamical forces.