发展中的地质科学

地质学是许多科学中建立和发展较早的一门学科,它曾在解决人类利用自然资源等方面起了巨大的作用。但是自70年代末以来,地质面临一些大的困难,例如地质学如何继续向前发展,以适应当代高科技飞速发展的形势和人类活动愈来愈高的需求,地质学家还面临着社会就业的问题。据粗略估计,从世界各国情况来看,大约1/4至1/3的地质专业毕业的人员要改营他业。如英国1989-1990年有不少学校取消了地质专业,或与他校合并,1990年第13届国际沉积学大会所在地——诺丁汉大学即取消了地质学专业。

剖开顽石方得玉 淘尽泥沙始见金——忆鄂尔多斯盆地的石油地质实验工作

一、成功和挫折带来的思考 鄂尔多斯盆地以她广袤的面积,巨厚的沉积岩系,多层位的油气显示,吸引着一代代地质工作者。但她又具有基底过于稳定,覆盖层过于平缓,岩相变化大,储集层物性差等致命弱点,增加了在这一地区找油的艰巨性。 解放后近40年,地质部、燃化部系统的石油地质队伍,走马灯式地你来我往、几上几下,旷日持久地盘桓于这一地区,足以说明这一地区的石油远景是令人依恋的,但它又是一块难以啃动的“硬骨头”。

Geochronology, petrogenesis and tectonic significance of Dahongliutan pluton in Western Kunlun orogenic belt, NW China

The Dahongliutan granitic pluton,in the eastern part of the West Kunlun orogenic belt,provides significant insights for studying the tectonic evolution of West Kunlun.This paper presents a systematic study of LA-ICP-MS zircon U Pb age,major and trace elements,Sr-Nd-Hf isotopes,and the first detailed Li isotope analysis of the Dahongliutan pluton.LA-ICP-MS zircon U Pb dating shows that the Dahongliutan granites were emplaced in the Late Triassic((213±2.1)Ma).Geochemical data show relatively high SiO2 contents(68.45 wt%73.62 wt%)and aluminum saturation index(A/CNK=1.111.21)indicates peraluminous high-K calc-alkaline granite.The Dahongliutan granites are relatively high in light rare earth elements(LREE)and large ion lithophile elements(LILEs)(e.g.,Rb,K,Th),and relatively depleted in high field strength elements(HFSEs)(e.g.,Nb,Ta,P,Ti).TheεNd(t)values range from 8.71 to 4.73,and(87Sr/86Sr)i=0.70870.71574.Zircons from the pluton yield 176Hf/177Hf values of 0.2826181 to 0.2827683,andεHf(t)values are around 0;the two-stage Hf model ages range from 0.974 to 1.307 Ga.Theδ7Li values are 0.76‰3.25‰,with an average of 2.53‰.Isotopic compositions of the pluton suggest a mixed trend between the partial melting of the Middle Proterozoic ancient crustal material and a juvenile mantle-derived material.This study infers that the Dahongliutan rock mass is formed in the post-collisional extension environment,when the collision between South Kunlun and the Tianshuihai terranes results in the closure of the Palaeo-Tethys.The mantle-derived magma results in partial melting of the lower crust.

Mesozoic high-K granitic rocks from the eastern Dabie Mountains,Central China and their geological implications

The Mesozoic high-K granitic intrusions from the eastern Dabie Mountains, Central China, can be divided into three superunits namely the Yaohe, Penghe and Huangbai superunits. The Yaohe superunit is compositionally dominated by quartz monzonite extending as a band in NW direction which is differently foliated, contains numerous dioritic enclaves and has been dated as 174 Ma. The Penghe superunit, widely distributed in the field, varies in composition but is dominated by quartz monzonitic and granitic rocks, which is massive in structure, has well developed with dioritic enclaves and is aged in 125-127 Ma. The Huangbai superunit is mainly composed of granitic composition which is massive in structure, rarely contains dioritic enclaves and is aged in 120-111 Ma. These three superunits of granitic intrusions can also be clearly distinguished in geochemistry. They have recorded an orogenic process of the Dabie Mountains from the end of regional metamorphism to the overprinting of the circum-Pacific tectonic regime.

The magmatic activity mechanism of the fossil spreading center in the Southwest sub-basin, South China Sea

Petrogeochemical data indicate that after the end of seafloor spreading,residual magmatic activity still exists in the deep basin of the South China Sea.By using different viscous structure models beneath the fossil spreading center of the Southwest sub-basin we simulated the amount of melt produced,the length of the melting period,and the thermal evolution process in terms of geothermics and the buoyant decompression melting mechanism.We compared the results of our model with observed heat flow,seismic,and petrogeochemistry data.The results show that depletion buoyancy induced by buoyant decompression melting plays an important role in the melting process,while retention buoyancy,thermal buoyancy,and viscous shear force have only a weak influence on the melting process.From the length of the melting period,we determined that for the three viscous structures models the magmatic activity lasted about 5,12,and 15 Ma.Under the effect of buoyant depression melting,local high-temperature areas will develop under the basin,which can explain the low-velocity layer detected by seismic exploration in the middle and upper lithosphere of the Southwest sub-basin.We also simulated the possible lithology distribution beneath the fossil spreading center with the physical conditions of different viscous structure,different temperature structure,and different melting fraction,which provided a greater understanding of the rock petrogeochemical data of the deep sea basin in the South China Sea.

Bio-Fertilizer,Ground Magnesium Limestone and Basalt Applications May Improve Chemical Properties of Malaysian Acid Sulfate Soils and Rice Growth

Acid sulfate soils are normally not suitable for crop production unless they are appropriately ameliorated. An experiment was conducted in a glasshouse to enhance the growth of rice, variety MR219, planted on an acid sulfate soil using various soil amendments.The soil was collected from Semerak, Kelantan, Malaysia. Ground magnesium limestone(GML), bio-fertilizer, and basalt(each 4t ha-1) were added either alone or in combinations into the soil in pots 15 d before transplanting. Nitrogen, P and potash were applied at 150, 30, and 60 kg ha-1, respectively. Three seven-day-old rice seedlings were transplanted into each pot. The soil had a p H of 3.8 and contained organic C of 21 g kg-1, N of 1.2 g kg-1, available P of 192 mg kg-1, exchangeable K of 0.05 cmol c kg-1,and exchangeable Al of 4.30 cmol c kg-1, with low amounts of exchangeable Ca and Mg(0.60 and 0.70 cmol c kg-1). Bio-fertilizer treatment in combination with GML resulted in the highest p H of 5.4. The presence of high Al or Fe concentrations in the control soil without amendment severely affected the growth of rice. At 60 d of growth, higher plant heights, tiller numbers and leaf chlorophyll contents were obtained when the bio-fertilizer was applied individually or in combination with GML compared to the control. The presence of beneficial bacteria in bio-fertilizer might produce phytohormones and organic acids that could enhance plant growth and subsequently increase nutrient uptake by rice. Hence, it can be concluded that addition of bio-fertilizer and GML improved rice growth by increasing soil p H which consequently eliminated Al and/or Fe toxicity prevalent in the acid sulfate soil.