Asynchronous infiltration-driven growth of forsterite and periclase during metamorphism in marbles of the inner Alta aureole, Utah: δ18O and textural records of oxygen isotope disequilibrium, rapid forsterite growth and reaction history
Asynchronous infiltration-driven growth of forsterite and periclase during metamorphism in marbles of the inner Alta aureole, Utah: δ18O and textural records of oxygen isotope disequilibrium, rapid forsterite growth and reaction history
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犹他州内阿尔塔光环大理石变质过程中镁橄榄石和方镁石的异步渗透驱动生长：δ18O 和氧同位素不平衡的结构记录、镁橄榄石快速生长和反应历史
DOI：
10.1007/s00410-022-01939-0
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发表时间：
2022
影响因子：
3.5
通讯作者：
Tapanila, Lorraine M.
中科院分区：
文献类型：
--
作者：
Beno, Carl J.;Bowman, John R.;Kitajima, Kouki;Valley, John W.;Loury, Patrick C.;Tapanila, Lorraine M.
渗透驱动的变质作用在犹他州阿尔塔接触光环的硅质白云岩中产生了广泛的镁橄榄石。二次离子质谱仪(SIMS)δ18O分析表明，在大部分中、外镁橄榄岩带样品中，镁橄榄石、方解石和白云石的δ18O在颗粒尺度上是均匀的，而镁橄榄石和方解石在薄片到手部尺度上表现出少量的 <； 1‰的晶间不均一性。相反，在火成岩接触带(内镁橄榄岩和方镁石带)的 ~ 300m范围内，镁橄榄岩中颗粒尺度的δ18O不均一性高达3.0‰，但由于骨架生长和充填，镁橄榄岩晶体的δ18O没有表现出从中心到边缘的系统性下降。除了一个例外，所有被分析的样品中的镁橄榄石、方解石和白云石都产生了不平衡分馏。镁橄榄岩、方解石和白云石之间普遍记录到的氧同位素不平衡可能反映了镁橄榄岩的快速生长，这可能是由于镁橄榄岩结晶完成后，在冷却初期，基质碳酸盐矿物中的18O/16O贫化导致的。在方镁石带含镁橄榄石和方镁石的大理岩层之间的导线上，镁橄榄石和方解石SIMS的δ18O剖面结合镁橄榄石结构的趋势表明，这些层不是同时渗透的，也不是在导致镁橄榄石和方镁石的两次进积反应期间连续渗透的。相反，结构和SIMS数据要求首先在镁橄榄岩大理岩层中渗透和形成镁橄榄石，然后在方镁石大理岩层中渗透和形成方镁石。因此，镁橄榄岩记录的δ~(18)O剖面比方解石记录的δ~(18)O剖面形成得早，但这两个剖面都是进积特征，即两个剖面都是响应进积反应而形成的，先形成镁橄榄岩，然后形成方镁石。这些颗粒尺度的δ18O剖面进一步表明，这些层经历了渗透率的显著变化，这与它们连续的渗透-反应历史有关。在碳酸盐岩岩性接触变质过程中，这些指示矿物在前进式加热过程中露头规模的非同步生长可能比目前所认识的更为常见。
Infiltration-driven metamorphism has produced the widespread development of forsterite in the siliceous dolomites of the Alta, Utah contact aureole. SIMS (secondary ion mass spectrometry) δ18O analyses show that in most of the middle to outer forsterite zone samples, forsterite, calcite and dolomite are homogenous in δ18O at the grain-scale, but forsterite and calcite exhibit minor intergranular heterogeneities of < 1‰ on the thin-section to hand sample-scales. In contrast, within ~ 300 m of the igneous contact (inner forsterite and periclase zones), grain-scale δ18O heterogeneities in forsterite are as large as 3.0‰, but forsterite crystals do not exhibit systematic center-to-edge decreases in δ18O due to skeletal growth and infilling. With one exception, forsterite, calcite and dolomite in all samples analyzed yield disequilibrium fractionations. The oxygen isotope disequilibrium commonly recorded among forsterite, calcite and dolomite may reflect the rapid growth of forsterite from increased reaction overstepping as temperature increased, or results from18O/16O depletion in the matrix carbonate minerals during continued fluid infiltration after forsterite crystallization was complete, during the initial stages of cooling in the forsterite zone. In a traverse across the boundary between forsterite- and periclase-bearing marble layers in the periclase zone, forsterite and calcite SIMS δ18O profiles combined with the trend in forsterite textures indicate that these layers were not infiltrated simultaneously, nor continuously during both prograde reactions responsible for forsterite and periclase. Rather, the texture and SIMS data require infiltration and formation of forsterite first in the forsterite marble layer, followed by infiltration and formation of periclase in the periclase marble layer. As a consequence, the δ18O profile recorded by forsterite formed earlier than the δ18O profile recorded by calcite, but both profiles are prograde features—that is, both profiles formed in response to prograde reactions forming first forsterite and then periclase. These grain-scale δ18O profiles further suggest that these layers experienced significant changes in permeability that are linked to their sequential infiltration-reaction history. The asynchronous growth of these index minerals at the outcrop-scale during prograde heating may be more common during contact metamorphism of carbonate lithologies than currently recognized.
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影响因子：
2.9
作者：
S. Cook;J. R. Bowman;C. Forster
通讯作者：
C. Forster
一维流体渗透过程中氧同位素交换的空间模式
影响因子：
5.2
作者：
J. R. Bowman;S. Willett
通讯作者：
S. Willett
犹他州布莱顿四边形地质图
DOI：
10.3133/gq534
发表时间：
1966
期刊：
Geologic Quadrangle
影响因子：
--
作者：
A. A. Baker
通讯作者：
A. A. Baker
影响因子：
3.5
作者：
Brenner, Dana C.;Passey, Benjamin H.;Viete, Daniel R.
通讯作者：
Viete, Daniel R.
犹他州瓦萨奇山脉中部火成岩的起源和位置
DOI：
--
发表时间：
2001
期刊：
影响因子：
--
作者：
T. A. Vogel;F. W. Cambray;K. Constenius
通讯作者：
K. Constenius