排序方式： 共有13条查询结果，搜索用时 93 毫秒
11.
Seagrass meadows from the Lakshadweep islands were mapped with the help of black and white aerial photographs. A maximum of 40 ha seagrass cover was estimated in the lagoon of Minicoy, followed by Kavaratti (34 ha). The total seagrass cover from six major islands of Lakshadweep was estimated to be 112 ha with standing crop of ca 800 metric tonnes. The dominant seagrass species observed wasThalassia hemprichii whileCymodocea rotundata, Halophila ovata, Syringodium isoetifolium andHalodule uninervis were common to these islands. 相似文献
12.
The correlation between specific meteorites and asteroids is a long-standing problem. The best-known correlation seems to
be the HED–Vesta, although several problems still remain to be solved. We report the spectral reflectance analysis (0.4–2.5 μm)
of a set of HED meteorites, taken from the RELAB database and three V-type asteroids, taken from MIT-UH-IRTF Joint Campaign
for NEO Reconnaissance. We used the Modified Gaussian Model to fit the spectra to a series of overlapping, modified Gaussian
absorptions. The fitted individual bands are validated against established laboratory calibrations. With spectral resolution
extending to the near-infrared, we are able to resolve the presence of both high-calcium pyroxene (HCP) and low-calcium pyroxene
(LCP) and, thus, use the HCP/(HCP + LCP) ratios to remotely trace igneous processing on the parent asteroids. A search of
this mineral provides a useful probe of differentiation. The high HCP/(HCP + LCP) ratios found require extensive differentiation
of these asteroids and/or their primordial parent body. The degree of melting obtained for the eucrites, using the former
ratio, is comparable with that obtained for all V-type asteroids here analyzed, suggesting a comparable geologic history. 相似文献
13.
胶东石城金矿床成矿流体特征及成矿作用 总被引：1，自引：1，他引：0
石城金矿位于胶东牟平-乳山成矿带南端,为多金属硫化物型金矿床。其成矿流体阶段可分为3个,相应的流体包裹体特征为:(1)成矿早期(第1阶段)富CO2包裹体;(2)主成矿期(第2阶段)H2O包裹体和含CO2包裹体;(3)成矿后期(第3阶段)H2O包裹体。第1阶段均一温度为256～360℃,盐度3.71%～6.88%NaCl,第2阶段均一温度为168～270℃,盐度4.49%～10.24%NaCl,第3阶段均一温度为123～178℃,盐度0.35%～7.59%NaCl。其中主成矿期为中低温、低盐度的CO2-H2O-NaCl流体体系。H、O同位素表明石城金矿成矿流体为岩浆水与大气水形成的混合热液,C、O同位素则反映了地幔富CO2流体参与了成矿作用,而S同位素进一步揭示了金矿的成矿物质来源为壳幔相互作用的结果。石城金矿的出现表明研究区至少存在两期成矿事件,早期成矿时代约120Ma,主要为石英+黄铁矿型矿石,晚期成矿时代小于111Ma,主要为多金属硫化物型矿石,以石城金矿为代表。 相似文献