摘要:

Volcanic‐hosted sulfide and barite mineralization with high Au content (19.3 ppm) was discovered by submersible study (Shinkai 2000) on the eastern floor of the Kita‐Bayonnaise submarine caldera on the Shichito‐Iwojima Ridge, Izu‐Ogasawara Arc, northwestern Pacific.

ISSN:1064-119X    

DOI:10.1080/10641199709379931

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

India has about 2 million km2of Exclusive Economic Zone (EEZ), which is nearly two‐thirds of her total land area. The mineral potential of the EEZ includes well‐known monazite‐ilmenite‐rutile placers on the east and west coasts, calcareous aggregates and sands in the shallow waters (especially in the Lakshadweep island group off the southwest coast), and phosphate mud and sediments (along the west coast, and possibly in the Andaman Sea). There is also potential for cobalt‐rich crusts in several locations, and for hydrothermal sulfide mineralization in the Andaman Sea. In addition, seawater components and hydrocarbon deposits in the offshore areas are already attracting expanded activity. To be able to exploit the mineral potential of the EEZ on a long‐term sustainable basis, it is necessary to investigate the nature of each type of deposit and to make an associated oceano‐graphic‐environmental evaluation. A good beginning has been made with respect to exploitation of the beach and offshore placers.

ISSN:1064-119X    

DOI:10.1080/10641199709379932

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A study of the echo peak amplitudes from known nodule areas is initiated to observe the acoustic response for varying nodule abundances and number densities. A statistical study of the peak amplitudes from different nodule areas confirms that the coefficient of variation is the highest for medium nodule abundance and number density. Echo fluctuation study based on the Rician probability density function (PDF) establishes that the non‐nodule sediment bottom contributes to less scattering, i.e., it is a microtopographic type, whereas scattering is dominant in the nodule‐bearing areas. The spectral studies are conducted on depth data of different areas. This study ensures that the signal scattering in the nodule bottom area is due to the nodules lying on the seabed rather than the large / small‐scale topographic variations. The study based on Poisson PDF for nodule area confirms this fact again. Agreement between the nodule distribution and the Poisson distribution parameter is clearly seen. Such a relation is not observed in the case of Rician density functions.

ISSN:1064-119X    

DOI:10.1080/10641199709379933

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Massive sulfide chimneys from two hydrothermal fields at 7°24'S and 16°43'S on the East Pacific Rise were investigated using microscopic and chemical methods. The studies reveal three stages of growth for chimneys derived from black smokers in both locations:

ISSN:1064-119X    

DOI:10.1080/10641199709379934

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A total of 1,014 measures of sediment shear strengths were measured by means of miniature vane shear and fall cone tests on five gravity cores collected in Eckernfo‐erde Bay, Baltic Sea. Paired t test was used to compare the shear strengths measured by the two methods. It was found that fall cone strength calculated with Wood's K60value (0.29) overestimates the vane shear strength by 0.15 kPa (a=0.001) and the sample mean of the fall cone strength is 4.1% higher than the mean of the vane shear strength. However, fall cone strength calculated with Hansbo's K60value (0.24) underestimates the vane shear strength by 0.88 kPa (a = 0.001), and the sample mean of the fall cone strength is 13.8% less than the mean of the vane shear strength. Both calculated fall cone strengths are significantly different from the vane shear strength, with a p value of less than 0.001. Regression analysis of the Echernfoerde Bay data indicates that a new K60value is 0.275 with a confidence interval (a = 0.01) from 0.2704 to 0.2786. Paired t test shows that there is no significant difference between miniature vane shear and fall cone tests for these samples if the fall cone strength is calculated with K60=0.275.

ISSN:1064-119X    

DOI:10.1080/10641199709379935

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:1064-119X    

DOI:10.1080/10641199709379930

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor