神奇公海上演“公地悲剧”

在我们这个人类和其他各种生物栖息的星球上,海洋面积占了71%,而在海洋中,深海面积占大多数,占到全球的一多半。海洋的平均深度约3800米,最大深度超过11000米,已知全球最深点位于太平洋西部的马里亚纳海沟为11034米。地球上的深海有2/3位于公海之中。正因为在公海,深海成为人们     

“蛟龙”潜水,再创纪录

北京时间2012年6月24日,中国＂蛟龙号＂载人潜水器在西太平洋的马里亚纳海沟试验海区进行载人潜水试验,首次突破7000米,达7020米,随后于6月27日第5次下潜再次刷新同类型潜水器下潜深度纪录,最大下潜深度7062米,这是世界同类型的载人潜水器的最大下潜深度。     

卡梅隆孤身入深洋

美国导演卡梅隆驾驶其单人深潜器“深海挑战者号”成功下潜至世界海洋的最深处——马里亚纳海沟的挑战者海渊底部。卡梅隆此次下潜的深度约合10898米，这是全世界海洋无可比拟的深度极限。卡梅隆在抵达洋底之后，以《国家地理》探险家和电影制作者的身份向海面上为他此次行动提供支持的团队成员们发出讯号：“各系统一切正常。”同时，这位探险家正“蜗居”在深潜器狭小的驾驶舱内，对这片陌生的神秘海底进行着考察，作为抵达关岛附近深邃海沟底部的第三个人，     

刊中刊

双重打击：引发汤加大海啸的因素 发生在2009年9月，席卷萨摩亚和北汤加群岛的海啸是由海沟外坡上的一次8级地震引起的，在这个地方，太平洋板块进入消减带时发生弯曲。这里最初被认为是该海啸的唯一来源，但一个更为复杂的画面却正在出现。两个小组报告了在几乎同一时间和地点发生的两次地震，它们被称为“一对触发的地震”。但不清楚的是这两次地震到底是哪个触发了哪个。不管是哪种情况，这两次地震都为在邻汤加消减带上偶尔发生的大型海啸提供了一个机制。     

吉林海沟金矿控矿构造特征及其演化

针对海沟金矿是大型石英脉型金矿床 ,矿体严格受走向NE -NNE的断裂构造控制 ,控矿构造应力作用方式有三种这一状况 ,阐述了其成矿期最大主压应力方向为NE向。说明控矿断裂构造在成矿阶段的应力处于张扭性状态 ,此应力状态有利于矿液充填、沉淀。并指出该区NE -NNE向断裂北端—海沟背斜的倾伏端是进一步工作的方向     

Tectonic geomorphology of the Ryukyu Trench-Arc-Backarc System： geological-geophysical exploration and mapping

Based on an analysis of full-cover multi-beam bathymetric data, seismic and sub-bottom profiling data, and other geological-geophysical data sets, the geomorphologic features of the Ryukyu trench-arc-backarc (T-A-BA) system are delineated, and a geomorphologic map of the system is compiled. The results show that the evolution and spatial distribution patterns of the geomorphologic types of the Ryukyu T-A-BA system are controlled mainly by tectonic movements. The tectonic geomorphologic characteristics of the Ryukyu Arc (RA) differ distinctly from those of the East China Sea (ECS) continental shelf and slope. In term of geological structures, RA consists of the Tokara volcanic ridge, the Ryukyu folded ridge, the fore-arc accretion-wedge ridge and the Amami Depression and the fore-arc depressions between the ridges, which is composed of a complex of alternating island-slope ridges and fault basins. The slope of the ECS is a passive continental margin with stepwise faults. The Okinawa Trough (OT) is a backarc rift in which tectonicmovements are intensive, with active volcanic and hydro-thermal eruptions and sea floor spreading. The development of geomorphic features of the OT is controlled by the central en echelon spreading axes, the faults along the ECS slope and the marginal faults to the west of the Tokara volcanic ridge. The geomorphic complex of the OT is arranged in the following pattern: the en echelon grabens and volcanic chains formed by rifting and spreading lie in the central part of the trough, the turbidite plains incliningwards from the slope foot of the ECS lie in the westeru-northwesteru parts of the OT, and the volcaniclastic deposit plains inclining westward-northwestwards from the western slope foot of the RA lie in the easteru-southeasteru parts of the OT. In term of tectonic geomorphology, the OT forms a natural division between the sheff of the ECS and the RA.     

Indentation tectonics in the accretionary wedge of middle Manila Trench

Based on the multibeam morpho-tectonic analysis of the Manila Trench accretionary wedge and its indentation tectonics and the contrasting researches with other geological and geophysical data, three tectonic zones of the wedge are established, faulting features, tectonic distribution and stress mechanism for the indentation tectonics are analyzed, oblique subduction along Manila Trench with convergent stress of NW55~ is presented, and the relationship of the ceasing of Eastern Subbasin spreading of South China Sea Basin to the formation of subduction zone of Manila Trench is discussed. By the model analysis and regional research, it is found that the seamount subduction along Manila Trench does not lead to the erosion of the accretionary wedge and the oblique subduction actually is a NWWtrending obduction of Luzon micro-plate that results from the NWW-trending displacement of the Philippine Sea plate.     

Serpentinization of peridotites from the southern Mariana forearc

A detailed petrologic and mineralogic study was carried out on serpentinized peridotites dredged from the southern landward slopes of the Mariana Trench, in order to reveal the serpentinization process of these unusual rocks and to identify the sole presence of the mineral lizardite. The constituent minerals of these southern Mariana forearc peridotites are olivine, amphibole and spinel, as well as serpentine, chlorite and talc. Compared with serpentinite seamounts, the serpentinized peridotites from the southern Mariana forearc are characterized by the absence of magnetite and brucite, and the common presence of talc; besides, the serpentine mineral variety is simplex, only lizardite. Combining mineral chemistry and mineral phase relationships, we conclude that (1) the absence of magnetite in the serpentinized peridotites is due to incomplete serpentinization, other than magnetite, the iron end-member in olivine forms Fe-rich brucite and Fe-rich serpentine; (2) brucite is not stable with high silica activity, reacting with later SiO₂-rich fluid and then forming lizardite, leading to a lack of brucite in these serpentinized peridotites; (3) the occurrence of talc is the result of later SiO₂-rich fluid reactions with lizardite; and (4) the reason for the sole occurrence of lizardite is that the temperature condition of our study area was not high enough for the formation of antigorite (which is stable at >500 °C). Despite the broad overlap of lizardite and chrysotile in growth temperature, differences in the modes of occurrence of lizardite and chrysotile, such as the scarcity of H₂O, low porosity and permeability, as well as the actual situation of initial serpentinization in the study area, result in the absolute prevalence of lizardite over chrysotile in the area.     

“蛟龙”号和深潜器的定义

2012年6—7月间,中国自主设计制造的深潜器“蛟龙”号在太平洋的马里亚纳海沟进行深海潜水试验,潜水深度达到水下7062米。这标志着中国已跻身国际“深潜俱乐部”,这个俱乐部的成员至今只有法国、美国、俄罗斯和日本。