Centre for Modern Physics, Chongqing University, Chongqing, 400044, China.
Mathematical Sciences Institute and Department of Theoretical Physics, Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 2601, Australia.
Sci Rep. 2018 Jan 11;8(1):559. doi: 10.1038/s41598-017-18908-4.
Ooids are typically spherical sediment grains characterised by concentric layers encapsulating a core. There is no universally accepted explanation for ooid genesis, though factors such as agitation, abiotic and/or microbial mineralisation and size limitation have been variously invoked. Here we examine the possible influence of microbial organomineralisation on the formation of some naturally occurring ooids. We develop a mathematical model for ooid growth, inspired by work on avascular brain tumours, that assumes mineralisation in a biofilm to form a central core which then nucleates the progressive growth of concentric laminations. The model predicts a limiting size with the sequential width variation of growth rings comparing favourably with those observed in experimentally grown ooids generated from biomicrospheres. In reality, this model pattern may be complicated during growth by syngenetic aggrading neomorphism of the unstable mineral phase, followed by diagenetic recrystallisation that further complicates the structure. Our model provides a potential key to understanding the genetic archive preserved in the internal structures of some ooids.
鲕粒通常是具有同心层的球形沉积物颗粒，其内部包裹着一个核心。鲕粒的成因尚无普遍接受的解释，但已提出各种因素，如搅动、生物和/或微生物矿化以及尺寸限制等。在这里，我们研究了微生物有机矿化对一些天然鲕粒形成的可能影响。我们根据无血管脑肿瘤的研究工作，为鲕粒的生长建立了一个数学模型，该模型假设在生物膜中矿化形成一个中心核心，然后核化同心层的渐进生长。该模型预测了一个限制尺寸，其生长环的顺序宽度变化与从生物微球生成的实验生长鲕粒中观察到的变化相当。实际上，在生长过程中，不稳定矿物相的同生加积蚀变以及随后的成岩重结晶可能会使这种模型模式变得复杂，从而进一步复杂化其结构。我们的模型为理解一些鲕粒内部结构中保存的遗传档案提供了一个潜在的关键。
