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【期刊论文】Occurrence of "monalbite" in nature: a TEM study
孟大维, Xiuling Wu a, *, Dawei Meng a, , Yujing Han b
Earth and Planetary Science Letters 222 (2004) 235-241,-0001,():
-1年11月30日
Natural "monalbite" (MA) has been observed on a submicron-scale in jadeite along with high albite (HA) and low albite (LA) in jadeite quartzite in the Dabie ultrahigh-pressure (UHP) metamorphic terrane, China. Transmission electron microscope (TEM) observation of inclusions in jadeite crystals has revealed mineral phases with C2/m and C1-structures. The cell parameters of the C2/m crystal structure correspond to those of MA, whereas the cell parameters of C1-structure are identical to those of HA and LA. The existence of the C2/m structure shows that the jadeite underwent partial change to MA on a submicron-scale during retrograde metamorphism. Albite transformation twinning of HA suggests the transformation of MA into HA. MA occurrence provides powerful evidence of high-temperature metamorphism during exhumation, probably above 930℃. The preservation of MA may be due to the armouring by the jadeite and implies a very rapid cooling (quenching) during retrogression.
monalbite, albite, jadeite, transmission electron microscope, Dabie Mountains, UHP metamorphism
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孟大维, WU Xiu ling, , MENG Da wei, MOU Tao, PAN Zhao lu
JOURNAL OF RARE EARTHS, 2000, Vol. 18, No.2,-0001,():
-1年11月30日
The domain structures in calcium cerium fluorocarbonate mineral series from a rare earth mineral deposit within an aegirine alkali granite massif in Mianning County, Sichuan Province, China, were studied by means of transmission electron microscopy. Many categories of domain structures in this mineral series were observed and in-vestigated, including the microtwin domains of parisite 6R2 and B2S 6R, the antiphase domains of B2S22H. The re-sults show that the antiphase domains which are faults along crystal plane (0001) are formed by the displacement of crystal lattice in c* direction and the displacement is 0.471nm. A new polytype (B4S2 3R) of regular mixed-layer structure with B4S2 type is found in the domain region of mixed layer structure.
rare earths, Ca Ce fluorocarbonate mineral, domain structure, polytype
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【期刊论文】Syntactic Intergrowth Structure in the Calcium Rare Earth Fluorocarbonate Minerals
孟大维, Wu Xiuling, Meng Dawei, Yang Guangming, Pan Zhaolu, Li Douxing, Dai Jiyan, Hu Kuiyi
JOURNAL OF RARE EARTHS, 1998, Vol. 16, No.3,-0001,():
-1年11月30日
The microst ructural characteristics of syntactic polycrystal in the calcium rare earth fluorocarbonate minerals f rom Southwest China have been studied by means of selected area elec t ron diff raction and high resolution elect ron microscopy (HREM). The complication of the hetero geneous fabric of the minerals have been revealed by HREM. The result s show that the crystal st ructure of the minerals was formed by a disorder stacking of the unit layers of bast naesite and synchisite in the calcium rare earth fluorocarbonate minerals along c direction. The stacking fault and other crystal defect s in the syntactic polycrystal have been discussed.
Rare earths, Calcium rare earth fluorocarbonate mineral, Syntactic intergrowth, High resolution electron microscopy
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【期刊论文】大别山双河硬玉石英岩石英中的纳米—亚微米级流体包裹体
孟大维, 吴秀玲, 韩郁菁, 韩勇, 郑建平
矿物岩石,2005,6(2):7-10,-0001,():
-1年11月30日
用透射电子显微镜(TEM)观察产于大别山双河地区含柯石英硬玉石英岩矿物石英中纳米级至亚微米级的流体包裹体超微观结构特征发现:大多数包裹体呈圆形或负晶形(粒径大多为10nm~350nm),构成宽的密集的包裹体串。TEM揭示了柯石英和寄主矿物石英之间为共晶格取向连生关系,并寻找到在峰期变质条件下高盐流体存在的有力证据。流体包裹体经常伴随着许多相互连接的位错,并且与位错和位错壁等交生在一起,形成网络分布,这是在光学显微镜尺度下所不能探测到的。非爆裂的流体渗漏可能通过H2O或CO2分子沿位错的管道扩散,从包裹体进入寄主矿物石英,因而导致原来包裹体密度和成分的变化。
超高压硬玉石英岩, 石英, 纳米级流体包裹体, TEM, 大别山
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孟大维, Xiuling Wu a;b, *, Yujing Han a, Dawei Meng a;b, Douxing Li b
Earth and Planetary Science Letters 197 (2002) 165-169,-0001,():
-1年11月30日
We present the results of high-resolution transmission electron microscope (HRTEM) studies on jadeite crystals of jadeite quartzite from the Dabie ultra-high-pressure (UHP) metamorphic terrane, China. Although jadeite is known to have only C2/c crystal structure, [100], [110], [112], [010] diffraction patterns and HRTEM images reveal C2/c and P21/n structures in 500 nm microdomains of single jadeite crystals, that we recognized in all the above four orientations. The cell parameters of C2/c crystal structure correspond to those of jadeite, whereas the cell parameters of P21/n structure are equivalent to those of omphacite. The presence of the P21/n structure shows that jadeite partially changed into omphacite on a nano-scale during retrograde metamorphism and that this reaction failed to reach equilibrium. It suggests uplift of the host rock during exhumation accompanied by complex non-equilibrium retrogressive process in the jadeite, with significant implications for the derivation of PT paths and tectonic interpretation of the Dabie UHP metamorphic terrane.
jadeite, omphacite, equilibrium, transmission electron microscope, Dabie Mountains
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