The Ediacaran Doushantuo Formation in Weng'an and Fuquan areas of the Guizhou Provincein southern China hosts high-grade phosphorus ore deposits and exceptionally well-preserved phosphaticmicrofossils that are commonly less than 1 mm in diameter. Earlier studies attributed these fossils to algaeor acritarchs. In the last decade, researchers found that the spherical microfossils, in a large proportion,show metazoan embryonic development features with early cleavage stages. Thus these sphericalmicrofossils have been considered as diploblast or triploblast embryos and resting eggs of early animals.However, reliable fossils similar to blastula, gastrula embryos, fossils of larvae after hatching, andparticularly, the corresponding body fossils of these animal embryos have never been found in the relevantstrata. This phenomenon challenges the interpretation that these globular microfossils are animal embryos.Because the major uncertainty on these fossils is whether they are animals or plants, a detailed geochemicalanalyses across the fossils may help to reveal the differences (between animal and plant) in the compositionof cell membrane / wall and cell inclusions, the pattern of physiological metabolism, and the phosphatizedmechanisms in particular depositional environments. On this basis and in combination with morphologicalcomparison with the Cambrian microfossils and modern metazoan embryos, elemental geochemistry acrossthe spherical microfossils ("embryos") of the Weng' an biota may provide new information for betterunderstanding the genetic affinity of the Doushantuo globular fossils. In this paper, the author analyzesthe microfossils collected from Weng' an and Fuquan areas in Guizhou by electron probe micro-analyzer(EPMA) to obtain trace elemental geochemistry across the globular fossils. For comparison purposes, twotypes of fossils have been analyzed, including fossils with tumor-like outer wall and those with polygonalplate-shaped outer wall. Comparing results from these fossils and their host rocks, preliminary findingsare as follows: (1) fossils with tumor-like and plate-shaped outer walls have similar trends in majorelement contents from inside to the outer wall, suggesting the same affinity of the two groups; (2)comparison with the host rocks, the globular fossils have higher P, Ca content and stronger capability of assimilation and accumulation for Na, Ni, Zn, and Cl, but less capacity for the absorption of Mg, K, Al,Si, Ti, Mn and Fe2+. In addition, fossils have high S content and are enriched in lanthanide elements (ie.La, Ce, Nd). Through these analyses, the author prefers to exclude the seaweed affinity of these fossils.However, due to the lack of comparative data related to metaz oan, the existing data is not sufficient to clarify the dispute on the classification of spherical microfossils.%本文利用电子探针微区分析技术(EPMA),首次分析了采自贵州瓮安北斗山磷矿区陡山沱组外壁呈瘤状及多边形板片状的磷酸盐化球状化石的元素地球化学含量,包括常量元素氧化物含量和部分稀土元素含量,经初步对比发现:具瘤状及板片状外壁的两类球状化石,由内至外常量元素含量的变化趋势大体相似,表明归人同一生物大门类的可能性较大;与磷块岩全岩样品相比,球状化石中除了P、Ca含量更高以外,Na、Ni、Zn和Cl有较高的含量,而且S含量和轻稀土元素Ce等含量均偏高,可能表明球状化石在趋于弱还原的沉积环境中被磷酸盐化保存;K、Al、Mg、Ti、Mn、Fe2+和Si等含量均显著低于围岩.由于还缺乏后生动物的相关对比资料,目前还不能为球状微体化石的生物学属性争议提供元素地球化学方面的确切对比意见,但分析的结果不倾向于归属藻类、硫细菌和海绵动物.这方面的尝试为深化球状化石的亲缘关系研究提供了新途径和新材料.
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