We have described the results of laboratory analyses of 42 horizontal tows using a Clarke-Bumpus plankton sampler with a 100 µ emmesh net in the Gulf Stream. Classifications of 20 zooplankton taxa have been made for the 42 hauls. Calanoids dominate the hauls. It was found that the zooplankton population distribution and density varied considerably from haul to haul, but there was no consistent buildup or depletion of population with progress of the flow north in the Gulf Stream. These biological arguments reinforce previous conjectures that there is a geostrophically-balanced inflow of continental shelf and Labrador Sea water that gradually mixes with the Gulf Stream water mass. These inflows provide sources of zooplankton and phytoplankton to the Gulf Stream as it progresses northward. Also, an ecological analysis of the Gulf Stream indicates that the dry organic matter is over an order of magnitude below that which is theoretically possible.
Mineral surveys were requested on part of the Southern Inyo Wilderness Study Area (CA-010-056) covering 27,240 acres on the west side of the southern Inyo Mountains.In this report, the area studied is referred to as "the wilderness study area", or simply "the study area".Fieldwork for this report was carried out between 1983 and 1985.No resources were identified at the 66 mines and prospects examined in and adjacent to the study area.Several areas have low and moderate resource potential for gold, silver, lead, and zinc.A zone extending from the Reward mine (near the northwest corner of the study area) 3 mi to the southeast has low and moderate resource potential for gold, silver, lead, and zinc.There is low potential for gold, silver, lead, and zinc resources in an area located about 1.5 mi northeast of the Reward mine.A mineralized shear zone on the north side of Union Wash, about 3 mi south of the Reward mine, has moderate resource potential for silver and lead on the west and low resource potential for gold, silver, lead, and zinc on the east.Two areas between Kern Knob and Dolomite Canyon along the southwest boundary of the study area and the south edge of the study area have low resource potential for silver, lead, and zinc.Low resource potential for gold, silver, lead, and zinc is indicated for the southwest flank of New York Butte on the east edge of the study area.There is low resource potential for talc in the area east of Kern Knob.The geology of the study area is also conducive to the formation of skarns, which form in carbonate rocks adjacent to large plutons.Anomalous concentrations of elements such as tungsten, molybdenum, and bismuth that are associated with skarns and the heavy minerals scheelite and pyrite were identified in geochemical samples from the study area and indicate this type of mineralization.Only small skarn deposits are known to exist in the study area, however.Talc is another type of deposit related to the contact-metamorphic effects of the large granitic plutons found in the study area.Small talc bodies were mined in and near the study area in the vicinity of Kern Knob (fig.2).There is low resource potential for talc east of Kern Knob.Geochemical and mineralogical evidence and an inventory of mines and prospects indicate that gold, silver, lead, and zinc mineralization has occurred in several places in the study area.Many of the mines and prospects examined in this study lie within these mineralized areas, although none have identified resources.A zone extending from the Reward mine area 3 mi to the southeast has low resource potential for gold, silver, lead, and zinc, and the immediate vicinity of the Reward mine has moderate resource potential for these elements (fig.2).An area of fissure veins in granitic rocks about 1.5 mi northeast of the Reward mine has low potential for gold, silver, lead, and zinc resources.An east-trending shear zone on the north side of Union Wash has moderate resource potential for silver and lead and low resource potential for gold and zinc on the west and low resource potential for gold, silver, lead, and zinc on the east (fig.2).There is low potential for silver, lead, and zinc resources along the southwest boundary of the study area extending from the upper part of Long John Canyon to Brooklyn Canyon and at the south end of the study area east of Dolomite Canyon.The southwest flank of New York Butte has low resource potential for gold, silver, lead, and zinc.118°05-APPROXIMATE BOUNDARY OF SOUTHERNINYO WILDERNESS STUDY AREA (CA-010-056) Au, Ag, Pb, Zn Au, Ag, Pb, Zn Ag, Pb (moderate) Qs Au, Zn (low) LEVELOF CERTAINTY Available information is not adequate for determination of the level of mineral resource potential.Available information suggests the level of mineral resource potential.Available information gives a good indication of the level of mineral resource potential.
Abstract Fluid seepage along obliquely deforming plate boundaries can be an important indicator of crustal permeability and influence on fault-zone mechanics and hydrocarbon migration. The ∼850-km-long Queen Charlotte fault (QCF) is the dominant structure along the right-lateral transform boundary that separates the Pacific and North American tectonic plates offshore southeastern Alaska (USA) and western British Columbia (Canada). Indications for fluid seepage along the QCF margin include gas bubbles originating from the seafloor and imaged in the water column, chemosynthetic communities, precipitates of authigenic carbonates, mud volcanoes, and changes in the acoustic character of seismic reflection data. Cold seeps sampled in this study preferentially occur along the crests of ridgelines associated with uplift and folding and between submarine canyons that incise the continental slope strata. With carbonate stable carbon isotope (δ13C) values ranging from −46‰ to −3‰, there is evidence of both microbial and thermal degradation of organic matter of continental-margin sediments along the QCF. Both active and dormant venting on ridge crests indicate that the development of anticlines is a key feature along the QCF that facilitates both trapping and focused fluid flow. Geochemical analyses of methane-derived authigenic carbonates are evidence of fluid seepage along the QCF since the Last Glacial Maximum. These cold seeps sustain vibrant chemosynthetic communities such as clams and bacterial mats, providing further evidence of venting of reduced chemical fluids such as methane and sulfide along the QCF.
In late 2013, Scripps Institution of Oceanography collected multibeam bathymetry and acoustic-backscatter data of the Inner Continental Borderland Region, Southern California. The U.S. Geological Survey Pacific Coastal and Marine Science Center processed these data, and this report provides the data in a number of different formats in addition to a set of map sheets. The data catalog provides the new bathymetry and acoustic-backscatter data, collected mainly in the Gulf of Santa Catalina and San Diego Trough, as well as this new bathymetry data merged with other publicly available bathymetry data from the region. Sheet 1 displays a colored shaded-relief bathymetry map of the Inner Continental Borderland generated from the merged bathymetry data. Sheet 2 displays the new acoustic-backscatter data along with other available backscatter data in the region. Sheet 3 displays selected perspective views of the bathymetry data highlighting submarine canyon and channel systems, knolls, and tectonic features.
Detailed, integrative field and laboratory studies of the textures, structures, chemical characteristics, and isotopically determined ages and signatures of mineralization of the Bayan Obo deposit provided evidence for the origin and characteristics favorable for its formation and parameters necessary for defining giant polymetallic deposits of hydrothermal origin. Bayan Obo is an epigenetic, metasomatic, hydrothermal rare earth element (REE)-Fe-Nb ore deposit that is hosted in the metasedimentary H8 dolostone marble of the Middle Proterozoic Bayan Obo Group. The metasedimentary sequence was deposited on the northern continental slope of the North China craton. The mine area is about 100 km south of the suture marking Caledonian subduction of the Mongolian oceanic plate from the north beneath the North China craton. The mineralogy of the deposit is very complex, consisting of more than 120 different minerals, some of which are epigenetic minerals introduced by hydrothermal solutions, and some of which are primary and secondary metamorphic minerals. The major REE minerals are monazite and bastnaesite, whereas magnetite and hematite are the dominant Fe-ore minerals, and columbite is the most abundant Nb mineral. Dolomite, alkali amphibole, fluorite, barite, aegirine augite, apatite, phlogopite, albite, and microcline are the most widespread gangue minerals. Three general types of ores occur at Bayan Obo: disseminated, banded, and massive ores. Broad zoning of these ore types occurs in the Main and East Orebodies. Disseminated ores are in the outermost zone, banded ores are in the intermediate zone, and massive ores are in the cores of the orebodies. On the basis of field relations, host rocks, textures, structures, and mineral assemblages, many varieties of these three types of ores have been recognized and mapped. Isotopic dating of monazite, bastnaesite, aeschynite, and metamorphic and metasomatic alkali amphiboles associated with the deposit provides constraints on the ages of mineralization and the history of the deposit. Textural relations, differences in chemical composition, and 232Th/208Pb internal isochron ages of monazite and bastnaesite samples indicate that many episodes of REE mineralization occurred at Bayan Obo, ranging from about 555 Ma to about 398 Ma. Initial 208Pb/204Pb ratios suggest different sources of REE's for different generations of REE minerals. Relative ages of Fe mineralization were deduced from textural relationships of Fe minerals with other, dated mineral phases in the deposit. Most Nb mineralization was in the area of the West Orebodies and resulted in disseminated ore. Aeschynite, an early stage of Nb mineralization (438+-25.1 Ma), occurs with huanghoite and alkali amphiboles in veins. The 40Ar/39Ar ages of amphiboles, as well as petrographic textures, were used to distinguish three periods of regional metamorphism in the Bayan Obo mine area: (1) Late Proterozoic, about 890 Ma, which recrystallized H8 carbonate to marble and crystallized lineated alkali amphiboles along foliation planes in the marble; (2) Caledonian, about 425-395 Ma, which resulted in metamorphic and metasomatic-metamorphic alkali amphiboles; and (3) Hercynian, about 300 Ma, based on biotite 40Ar/39Ar analyses from biotite schist and folded banded ores. The 40Ar/39Ar ages of metasomatic alkali amphiboles also place time constraints on the hydrothermal history of the ore deposit. Metasomatic amphiboles represent periods of intense hydrothermal activity, which began as early as 1.26 Ga; that date is based on the age of amphibole from a vein that crosscuts the H6 quartzite that underlies the H8 dolostone marble. Although much of the metasomatic amphibole formed during periods that overlapped the peak period of REE mineralization of banded ores, REE and alkali amphibole phases generally occur in different mineral assemblages or are of very different ages in the same assemblage and, therefore, may have been derived from
In February 2016 the University of Washington in cooperation with the U.S. Geological Survey, Pacific Coastal and Marine Science Center (USGS, PCMSC) collected multibeam bathymetry and acoustic-backscatter data in and near the Catalina Basin, southern California aboard the University of Washington's Research Vessel Thomas G. Thompson. Data was collected using a Kongsberg EM300 multibeam echosounder hull-mounted to the 274-foot R/V Thomas G. Thompson. The USGS, PCMSC processed these data and produced a series of bathymetric surfaces and acoustic-backscatter images for scientific research purposes. This data release provides a 10-m resolution bathymetry surface and a 10-m resolution acoustic backscatter image. In addition, a 25-m resolution bathymetry surface produced from this work was merged with publicly available multibeam bathymetry data as well as 2015, 2016, and 2017 multibeam bathymetry data collected in the continental borderland region by the Ocean Exploration Trust's Nautilus Exploration Program. The USGS, PCMSC processed the survey line files received from the Nautilus Exploration Program to include in an overall merged 25-m multibeam bathymetry surface of the northern portion of the Southern California Borderland region that is also available in this data release. These data can be used to assess the hazards posed by offshore faults, submarine landslides, and tsunamis as well as map sediment transport pathways and sedimentary sinks.
