Many of the approaches in petrochronology are rooted in the assumption of equilibrium. Diffusion is an expression of disequilibrium: the movement of mass in response to chemical potential gradients, and isotopes in response to isotopic gradients. It is extremely important that we be aware of how the effects of diffusion can place obstacles across our path towards petrochronologic enlightenment. Conversely the effects of diffusion also provide opportunities for understanding rates, processes, and conditions experienced by rocks. The enormity of the field does not permit us to provide a comprehensive review of either the mathematics of diffusion or quantitative data that have been obtained relevant to the interpretation of diffusive processes in rocks and minerals. Many resources cover these topics, including RiMG volume 72 ( Diffusion in Minerals and Melts ; Zhang and Cherniak 2010) and several textbooks (Crank 1975; Glicksman 2000). Particularly relevant to the discussion of petrochronology are summaries of the theory and controls on diffusion (Brady and Cherniak 2010; Zhang 2010), as well as diffusion rates in feldspar (Cherniak 2010a), accessory minerals (Cherniak 2010b), garnet (Ganguly 2010), mica, pyroxene, and amphibole (Cherniak and Dimanov 2010), and melts (Zhang and Ni 2010; Zhang et al. 2010). Rather than duplicate that material, our goal is to explore the obstacles and opportunities presented by the effects of diffusion as they inform the rates of petrologic processes. To achieve this goal, we emphasize key principles and illustrative examples. Quantitative interpretation of the effects of diffusion assumes predictability of numerous factors that may affect chemical or isotopic transport, including temperature, initial and boundary conditions, water and oxygen fugacities, activities of other components, multiple mechanisms of diffusion, and crystal chemistry (‘coupling’ of the substitution of elements into different crystallographic sites). Additionally, the extraction of meaningful ages, durations of events, and temperatures requires …
岩石年代学中的许多方法都是建立在平衡假设的基础上的。扩散是不平衡的一种表现:质量的运动响应于化学势梯度，同位素响应于同位素梯度。非常重要的是，我们要意识到扩散的影响如何在我们走向岩石年代学启蒙的道路上设置障碍。相反，扩散效应也为了解岩石的速率、过程和条件提供了机会。这一领域的巨大范围不允许我们对扩散的数学或已获得的与解释岩石和矿物中的扩散过程有关的定量数据进行全面审查。许多资源涵盖了这些主题，包括环第七十二卷(矿物和熔体的扩散;Zhang and Cherniak 2010)和一些教科书(曲克1975;Glicksman 2000)。与岩石年代学的讨论特别相关的是对扩散的理论和控制的总结(Brady and Cherniak 2010;Zhang 2010)，以及长石(Cherniak 2010a)、副矿物(Cherniak 2010b)、石榴石(Ganguly 2010)、云母、辉石、角闪石(Cherniak and Dimanov 2010)和熔体(Zhang and Ni 2010;Zhang et al. 2010)。我们的目标不是重复这些材料，而是探索扩散效应所带来的障碍和机会，因为它们通知了岩石过程的速率。为了实现这一目标，我们强调关键原则和说明性例子。扩散效应的定量解释假设了许多可能影响化学或同位素传输的因素的可预测性，包括温度、初始和边界条件、水和氧的逸度、其他组分的活性、多种扩散机制和晶体化学(元素取代到不同晶体位置的“耦合”)。此外，提取有意义的年龄、事件持续时间和温度需要……
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Friendship does indeed make us fresh—fresh in our enthusiasm, fresh in our creativity, and fresh in our collaborative potential. Indeed, it is the growing friendship between petrology and geochronology that has given rise to the new field of petrochronology. This, in turn, has opened a new array of methods to investigate the history of the geologic processes that are encoded (oh, so tantalizingly close!) in rocks, and to develop a broad new array of questions about those processes. All friendships have their initiations …
{"title":"“Thy friendship makes us fresh”: Charles, King of France, Act III, Scene III (Henry VI, Part 1, by William Shakespeare)","authors":"M. Kohn, M. Engi, P. Lanari","doi":"10.2138/RMG.2017.83.0","DOIUrl":"https://doi.org/10.2138/RMG.2017.83.0","url":null,"abstract":"Friendship does indeed make us fresh—fresh in our enthusiasm, fresh in our creativity, and fresh in our collaborative potential. Indeed, it is the growing friendship between petrology and geochronology that has given rise to the new field of petrochronology. This, in turn, has opened a new array of methods to investigate the history of the geologic processes that are encoded (oh, so tantalizingly close!) in rocks, and to develop a broad new array of questions about those processes.\u0000\u0000All friendships have their initiations …","PeriodicalId":49624,"journal":{"name":"Reviews in Mineralogy & Geochemistry","volume":"72 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86330242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The magmatic processes that fuel volcanism, crustal growth, ore formation and discharge of volcanic gases and aerosols to the atmosphere occur across a range of timescales, from millions of years to just a few seconds. For example, the production of new oceanic crust at mid-ocean ridges is a near-continuous process that can operate in any one ocean basin on timescales of more than 100 m.y. However, the driving force for such processes is the spreading of the ocean plates that happens on a cm/yr timescale. At the other end of the spectrum, explosive volcanic eruptions involve the ascent and fragmentation of magma at velocities of the order of 100 m/s such that the journey from a magma chamber to an ash cloud may take place in a matter of minutes. In this case the driving force is the rapid expansion of magmatic gas in response to changes in pressure. At intermediate timescales magmatic processes may give rise to hydrothermal ore deposits on timescales of less than a million years for an individual deposit, while growth of giant granite batholiths may require piecemeal assembly of magma batches on timescales of a few million years. Although each of these processes has a characteristic, time-averaged timescale on which it operates, this is typically the end result of one or more natural processes that operate on much shorter timescales. For example, mid-ocean ridges do not extrude magma continuously onto the ocean floor, mineralising fluids do not discharge continuously through the shallow crust, and granitic magmas do not dribble continuously into evolving batholithic chambers. In some cases it is the long-term timescales that are important, for example the spreading rate of ocean basins, in others it is the short-term timescales that are important, for example the episodic growth of lava domes at active volcanoes. Although …
{"title":"Chronometry and Speedometry of Magmatic Processes using Chemical Diffusion in Olivine, Plagioclase and Pyroxenes","authors":"R. Dohmen, K. Faak, J. Blundy","doi":"10.2138/RMG.2017.83.16","DOIUrl":"https://doi.org/10.2138/RMG.2017.83.16","url":null,"abstract":"The magmatic processes that fuel volcanism, crustal growth, ore formation and discharge of volcanic gases and aerosols to the atmosphere occur across a range of timescales, from millions of years to just a few seconds. For example, the production of new oceanic crust at mid-ocean ridges is a near-continuous process that can operate in any one ocean basin on timescales of more than 100 m.y. However, the driving force for such processes is the spreading of the ocean plates that happens on a cm/yr timescale. At the other end of the spectrum, explosive volcanic eruptions involve the ascent and fragmentation of magma at velocities of the order of 100 m/s such that the journey from a magma chamber to an ash cloud may take place in a matter of minutes. In this case the driving force is the rapid expansion of magmatic gas in response to changes in pressure. At intermediate timescales magmatic processes may give rise to hydrothermal ore deposits on timescales of less than a million years for an individual deposit, while growth of giant granite batholiths may require piecemeal assembly of magma batches on timescales of a few million years. Although each of these processes has a characteristic, time-averaged timescale on which it operates, this is typically the end result of one or more natural processes that operate on much shorter timescales. For example, mid-ocean ridges do not extrude magma continuously onto the ocean floor, mineralising fluids do not discharge continuously through the shallow crust, and granitic magmas do not dribble continuously into evolving batholithic chambers. In some cases it is the long-term timescales that are important, for example the spreading rate of ocean basins, in others it is the short-term timescales that are important, for example the episodic growth of lava domes at active volcanoes. Although …","PeriodicalId":49624,"journal":{"name":"Reviews in Mineralogy & Geochemistry","volume":"2016 1","pages":"535-575"},"PeriodicalIF":0.0,"publicationDate":"2017-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86692997","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The inspiration for this volume arose in part from a shift in perception among U–Pb geochronologists that began to develop in the late 1980s. Prior to then, analytical geochronology emphasized progressively lower blank analysis of separated accessory mineral aggregates (e.g., Krogh 1982; Parrish 1987), with results generally interpreted to reflect a singular moment in time. For example, a widespread measure of confidence in intra-analytical reliability was conformity to an MSWD (a form of χ2 test; Wendt and Carl 1991) of unity. This approach implicitly assumed that geological processes act on timescales that are short with respect to analytical errors (e.g., Schoene et al. 2015). As in situ methodologies (e.g., Compston and Pidgeon 1986; Harrison et al. 1997; Griffin et al. 2000) and increasingly well-calibrated double spikes (e.g., Amelin and Davis 2006; McLean et al. 2015) emerged, geochronologists began to move away from interpreting geological processes as a series of instantaneous episodes (e.g., Rubatto 2002). At about the same time, petrologists developed techniques that permitted in situ chemical analyses to be interpreted in terms of continuously changing pressure–temperature–time histories (e.g., Spear 1988). The recognition followed that specific mineral reactions yielded products that could be directly dated or interpreted in terms of protracted petrogenetic processes. Part of this shift was due to an appreciation that trace elements in accessory phases could identify the changing nature of modal mineralogy during crystal growth (e.g., Pyle et al. 2001; Kohn and Malloy 2004) and thus potentially relate petrogenesis to absolute time. The transition to petrochronology was complete upon recognition that high MSWDs were in fact the expected case for most metamorphic minerals (Kohn 2009). One of the great frontiers for fundamental discovery in the geosciences is earliest Earth (DePaolo et al. 2008). However, investigations of the first five …
这本书的灵感部分来自于20世纪80年代末开始发展的U-Pb地质年代学家的观念转变。在此之前，分析地质年代学逐渐强调分离的辅助矿物团聚体的较低空白分析(例如，Krogh 1982;Parrish 1987)，其结果通常被解释为反映一个单一的时刻。例如，分析内信度的广泛置信度是符合MSWD (χ2检验的一种形式;温特和卡尔1991)的统一。这种方法隐含地假设地质过程在相对于分析误差而言较短的时间尺度上起作用(例如，Schoene et al. 2015)。就地方法(例如，Compston和Pidgeon 1986;Harrison et al. 1997;Griffin et al. 2000)和越来越精确的双尖峰(例如，Amelin and Davis 2006;McLean et al. 2015)的出现，地质年代学家开始不再将地质过程解释为一系列瞬时事件(例如，Rubatto 2002)。大约在同一时期，岩石学家开发了一种技术，可以根据连续变化的压力-温度-时间历史来解释现场化学分析(例如，Spear 1988)。随后认识到，特定的矿物反应产生的产物可以直接确定年代，或根据长期的岩石形成过程进行解释。这种转变的部分原因是人们认识到，辅助相中的微量元素可以识别晶体生长过程中模态矿物学性质的变化(例如，Pyle等人，2001;Kohn and Malloy 2004)，因此可能将岩石成因与绝对时间联系起来。在认识到高mswd实际上是大多数变质矿物的预期情况后，向岩石年代学的过渡就完成了(Kohn 2009)。地球科学基础发现的伟大前沿之一是最早的地球(DePaolo et al. 2008)。然而，对前五名的调查……
{"title":"Hadean Zircon Petrochronology","authors":"T. Harrison, E. Bell, P. Boehnke","doi":"10.2138/RMG.2017.83.11","DOIUrl":"https://doi.org/10.2138/RMG.2017.83.11","url":null,"abstract":"The inspiration for this volume arose in part from a shift in perception among U–Pb geochronologists that began to develop in the late 1980s. Prior to then, analytical geochronology emphasized progressively lower blank analysis of separated accessory mineral aggregates (e.g., Krogh 1982; Parrish 1987), with results generally interpreted to reflect a singular moment in time. For example, a widespread measure of confidence in intra-analytical reliability was conformity to an MSWD (a form of χ2 test; Wendt and Carl 1991) of unity. This approach implicitly assumed that geological processes act on timescales that are short with respect to analytical errors (e.g., Schoene et al. 2015). As in situ methodologies (e.g., Compston and Pidgeon 1986; Harrison et al. 1997; Griffin et al. 2000) and increasingly well-calibrated double spikes (e.g., Amelin and Davis 2006; McLean et al. 2015) emerged, geochronologists began to move away from interpreting geological processes as a series of instantaneous episodes (e.g., Rubatto 2002). At about the same time, petrologists developed techniques that permitted in situ chemical analyses to be interpreted in terms of continuously changing pressure–temperature–time histories (e.g., Spear 1988). The recognition followed that specific mineral reactions yielded products that could be directly dated or interpreted in terms of protracted petrogenetic processes. Part of this shift was due to an appreciation that trace elements in accessory phases could identify the changing nature of modal mineralogy during crystal growth (e.g., Pyle et al. 2001; Kohn and Malloy 2004) and thus potentially relate petrogenesis to absolute time. The transition to petrochronology was complete upon recognition that high MSWDs were in fact the expected case for most metamorphic minerals (Kohn 2009).\u0000\u0000One of the great frontiers for fundamental discovery in the geosciences is earliest Earth (DePaolo et al. 2008). However, investigations of the first five …","PeriodicalId":49624,"journal":{"name":"Reviews in Mineralogy & Geochemistry","volume":"213 1","pages":"329-363"},"PeriodicalIF":0.0,"publicationDate":"2017-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89111936","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zircon (ZrSiO4) and baddeleyite (ZrO2) are common accessory minerals in igneous rocks of felsic to mafic composition. Both minerals host trace elements substituting for Zr, among them Hf, Th, U, Y, REEs and many more. The excellent chemical and physical resistivity of zircon makes this mineral a perfect archive of chemical and temporal information to trace geological processes in the past, utilizing the outstanding power and temporal resolution of the U–Pb decay schemes. Baddeleyite is a chemically and physically much more fragile mineral. It preserves similar information only where it is shielded from dissolution and physical fragmentation as an inclusion in other minerals or in a fine-grained or non-reactive rock matrix. It offers the potential for dating the solidification of mafic rocks with high-precision through its crystallization in small pockets of Zr-enriched melt, after extensive olivine and pyroxene fractionation. Zircon and baddelelyite U–Pb dates are, for an overwhelming majority of cases and where we can assume a closed system, considered to reflect the time of crystallization. The development of the U–Pb dating tool CA-ID-TIMS (chemical abrasion-isotope dilution-thermal ionization mass spectrometry) since 2005 has led to unprecedented precision of better than 0.1% in 206Pb/238U dates (Bowring et al. 2005). Increased sensitivity of mass spectrometers and low laboratory blanks due to reduction of acid volumes allow routine U–Pb age determinations of micrograms of material at sufficiently high radiogenic/common lead ratios (see Schoene and Baxter 2017, this volume). In situ U–Pb age analysis using laser ablation or primary ion beam sputtering allows analysis of sub-microgram quantities of zircon material from polished internal sections or zircon surfaces with spot diameters ranging from ~30 μm for laser-ablation, inductively coupled plasma mass spectrometry (LA-ICP-MS) to 10 μm for secondary ion mass spectrometry (SIMS), lateral resolutions of 2–5 μm for NanoSIMS …
锆石(ZrSiO4)和坏辉石(ZrO2)是长英质-基性火成岩中常见的副矿物。这两种矿物都含有取代Zr的微量元素，其中包括Hf、Th、U、Y、ree等。锆石优异的化学和物理电阻率使这种矿物成为一个完美的化学和时间信息档案，可以利用U-Pb衰变方案的出色功率和时间分辨率来追踪过去的地质过程。坏辉石是一种化学上和物理上都脆弱得多的矿物。只有当它与其他矿物或细粒或非反应性岩石基质中的包裹体一样不受溶解和物理破碎的影响时，它才保留类似的信息。它提供了在广泛的橄榄石和辉石分馏后，通过富锆熔体小袋中的结晶，以高精度确定基性岩石凝固年代的潜力。在绝大多数情况下，锆石和坏橄榄石的U-Pb年龄反映了结晶的时间，我们可以假设这是一个封闭的系统。自2005年以来，U-Pb测年工具CA-ID-TIMS(化学磨损-同位素稀释-热电离质谱)的发展使206Pb/238U测年的精度达到了前所未有的0.1%以上(Bowring et al. 2005)。由于酸体积减少，质谱仪的灵敏度提高，实验室空白减少，因此可以在足够高的放射性/普通铅比下对微克级物质进行常规U-Pb年龄测定(见Schoene和Baxter 2017，本卷)。使用激光烧蚀或一次离子束溅射进行原位U-Pb年龄分析，可以从抛光的内部切片或锆石表面分析亚微克数量的锆石材料，光斑直径范围从激光烧蚀的~30 μm，电感耦合等离子体质谱(LA-ICP-MS)到二次离子体质谱(SIMS)的10 μm，纳米SIMS的横向分辨率为2-5 μm…
{"title":"Petrochronology of Zircon and Baddeleyite in Igneous Rocks: Reconstructing Magmatic Processes at High Temporal Resolution","authors":"U. Schaltegger, J. Davies","doi":"10.2138/RMG.2017.83.10","DOIUrl":"https://doi.org/10.2138/RMG.2017.83.10","url":null,"abstract":"Zircon (ZrSiO4) and baddeleyite (ZrO2) are common accessory minerals in igneous rocks of felsic to mafic composition. Both minerals host trace elements substituting for Zr, among them Hf, Th, U, Y, REEs and many more. The excellent chemical and physical resistivity of zircon makes this mineral a perfect archive of chemical and temporal information to trace geological processes in the past, utilizing the outstanding power and temporal resolution of the U–Pb decay schemes. Baddeleyite is a chemically and physically much more fragile mineral. It preserves similar information only where it is shielded from dissolution and physical fragmentation as an inclusion in other minerals or in a fine-grained or non-reactive rock matrix. It offers the potential for dating the solidification of mafic rocks with high-precision through its crystallization in small pockets of Zr-enriched melt, after extensive olivine and pyroxene fractionation. Zircon and baddelelyite U–Pb dates are, for an overwhelming majority of cases and where we can assume a closed system, considered to reflect the time of crystallization.\u0000\u0000The development of the U–Pb dating tool CA-ID-TIMS (chemical abrasion-isotope dilution-thermal ionization mass spectrometry) since 2005 has led to unprecedented precision of better than 0.1% in 206Pb/238U dates (Bowring et al. 2005). Increased sensitivity of mass spectrometers and low laboratory blanks due to reduction of acid volumes allow routine U–Pb age determinations of micrograms of material at sufficiently high radiogenic/common lead ratios (see Schoene and Baxter 2017, this volume).\u0000\u0000In situ U–Pb age analysis using laser ablation or primary ion beam sputtering allows analysis of sub-microgram quantities of zircon material from polished internal sections or zircon surfaces with spot diameters ranging from ~30 μm for laser-ablation, inductively coupled plasma mass spectrometry (LA-ICP-MS) to 10 μm for secondary ion mass spectrometry (SIMS), lateral resolutions of 2–5 μm for NanoSIMS …","PeriodicalId":49624,"journal":{"name":"Reviews in Mineralogy & Geochemistry","volume":"5 1","pages":"297-328"},"PeriodicalIF":0.0,"publicationDate":"2017-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74349424","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Plate tectonic forcing leads to changes in the physical conditions that affect the lithosphere. In response to such changes, notably the local temperature ( T ) and pressure ( P ), rocks evolve dynamically. Processes mostly involve mineral transformations, i.e., solid-state reactions, but (hydrous) fluids are often involved, and partial melting may occur in the Earth’s middle and lower crust. While these chemical reactions reflect the tendency of natural systems to reduce their Gibbs free energy, metamorphic rocks commonly preserve textural and mineralogical relics, such as compositionally zoned minerals. Where relics are present, thermodynamic equilibrium clearly was not attained during the evolution of the rock. Petrochronology seeks to establish a temporal framework of petrologic evolution, and for this purpose it is essential to determine the P–T conditions prevailing at several stages. When analyzing a rock sample it is thus critical: 1. to recognize whether several stages of its evolution can be discerned, 2. to document the minerals that formed or were coexisting at each stage, and 3. to estimate at what physical conditions this happened. If (and only if) a chronometer then can be associated to one of these stages—or better yet several chronometers to different stages—then the power of petrochronology becomes realizable. This chapter is concerned with a basic dilemma that results directly from steps (b) and (c) above: P–T conditions are determined on the basis of mineral barometers and thermometers, which mostly rest on the assumption of chemical (or isotopic) equilibrium, yet the presence of relics is proof that thermodynamic equilibrium was not attained. One way out of the dilemma is to analyze reaction mechanisms and formulate a model based on non-equilibrium thermodynamics and kinetics (Lasaga 1998). While this can be fruitful for understanding fundamental aspects of metamorphic petrogenesis, there are more direct ways to address the limited scope needed for petrochronology. The alternative pursued …
{"title":"Local Bulk Composition Effects on Metamorphic Mineral Assemblages","authors":"P. Lanari, M. Engi","doi":"10.2138/RMG.2017.83.3","DOIUrl":"https://doi.org/10.2138/RMG.2017.83.3","url":null,"abstract":"Plate tectonic forcing leads to changes in the physical conditions that affect the lithosphere. In response to such changes, notably the local temperature ( T ) and pressure ( P ), rocks evolve dynamically. Processes mostly involve mineral transformations, i.e., solid-state reactions, but (hydrous) fluids are often involved, and partial melting may occur in the Earth’s middle and lower crust. While these chemical reactions reflect the tendency of natural systems to reduce their Gibbs free energy, metamorphic rocks commonly preserve textural and mineralogical relics, such as compositionally zoned minerals. Where relics are present, thermodynamic equilibrium clearly was not attained during the evolution of the rock.\u0000\u0000Petrochronology seeks to establish a temporal framework of petrologic evolution, and for this purpose it is essential to determine the P–T conditions prevailing at several stages. When analyzing a rock sample it is thus critical: \u0000\u00001. to recognize whether several stages of its evolution can be discerned,\u0000\u00002. to document the minerals that formed or were coexisting at each stage, and\u0000\u00003. to estimate at what physical conditions this happened.\u0000\u0000If (and only if) a chronometer then can be associated to one of these stages—or better yet several chronometers to different stages—then the power of petrochronology becomes realizable.\u0000\u0000This chapter is concerned with a basic dilemma that results directly from steps (b) and (c) above: P–T conditions are determined on the basis of mineral barometers and thermometers, which mostly rest on the assumption of chemical (or isotopic) equilibrium, yet the presence of relics is proof that thermodynamic equilibrium was not attained. One way out of the dilemma is to analyze reaction mechanisms and formulate a model based on non-equilibrium thermodynamics and kinetics (Lasaga 1998). While this can be fruitful for understanding fundamental aspects of metamorphic petrogenesis, there are more direct ways to address the limited scope needed for petrochronology. The alternative pursued …","PeriodicalId":49624,"journal":{"name":"Reviews in Mineralogy & Geochemistry","volume":"295 1","pages":"55-102"},"PeriodicalIF":0.0,"publicationDate":"2017-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78889315","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The goal of petrochronology is to extract information about the rates and conditions at which rocks and magmas are transported through the Earth’s crust. Garnering this information from the rock record greatly benefits from integrating textural and compositional data with radiometric dating of accessory minerals. Length scales of crystal growth and diffusive transport in accessory minerals under realistic geologic conditions are typically in the range of 1–10’s of μm, and in some cases even substantially smaller, with zircon having among the lowest diffusion coefficients at a given temperature (e.g., Cherniak and Watson 2003). Intrinsic to the compartmentalization of geochemical and geochronologic information from intra-crystal domains is the requirement to determine accessory mineral compositions using techniques that sample at commensurate spatial scales so as to not convolute the geologic signals that are recorded within crystals, as may be the case with single grain or large grain fragment analysis by isotope dilution thermal ionization mass spectrometry (ID-TIMS; e.g., Schaltegger and Davies 2017, this volume; Schoene and Baxter 2017, this volume). Small crystals can also be difficult to extract by mineral separation techniques traditionally used in geochronology, which also lead to a loss of petrographic context. Secondary Ionization Mass Spectrometry, that is SIMS performed with an ion microprobe, is an analytical technique ideally suited to meet the high spatial resolution analysis requirements that are critical for petrochronology (Table 1). View this table: Table 1 Advantages and limitations of in-situ SIMS analysis for petrochronology in comparison with other isotope selective methods In SIMS, bombardment of solid targets with an energetic ion beam removes atoms from the sample where primary ions are implanted into the target material to a depth of < 5–10 nm. Lateral resolution is controlled by primary ion beam dimensions (sub-μm to few 10’s of μm) with an upper limit set by the acceptance …
岩石年代学的目标是提取有关岩石和岩浆在地壳中运输的速率和条件的信息。从岩石记录中获得这些信息，极大地得益于将结构和成分数据与辅助矿物的放射性测年相结合。在实际地质条件下，辅助矿物的晶体生长和扩散运输的长度尺度通常在1-10 μm的范围内，在某些情况下甚至要小得多，锆石在给定温度下具有最低的扩散系数(例如，Cherniak和Watson 2003)。从晶体内域划分地球化学和地质年代学信息的本质是，需要使用在相应空间尺度上取样的技术来确定辅助矿物成分，以避免混淆晶体内记录的地质信号，就像用同位素稀释热电离质谱(ID-TIMS)分析单粒或大粒碎片一样。例如，Schaltegger and Davies 2017，本卷;Schoene and Baxter 2017，本卷)。小晶体也很难通过传统的地质年代学中使用的矿物分离技术提取出来，这也导致了岩石学背景的丢失。二次电离质谱，即用离子探针进行的SIMS，是一种非常适合满足对岩石年代学至关重要的高空间分辨率分析要求的分析技术(表1)。查看此表:表1与其他同位素选择方法相比，原位SIMS岩石年代学分析的优点和局限性。用高能离子束轰击固体目标，将原子从样品中移除，其中初级离子被植入目标材料至< 5-10 nm的深度。横向分辨率由主离子束尺寸(亚μm到10 μm)控制，上限由接收值决定。
{"title":"Secondary Ionization Mass Spectrometry Analysis in Petrochronology","authors":"A. Schmitt, J. Vazquez","doi":"10.2138/RMG.2017.83.7","DOIUrl":"https://doi.org/10.2138/RMG.2017.83.7","url":null,"abstract":"The goal of petrochronology is to extract information about the rates and conditions at which rocks and magmas are transported through the Earth’s crust. Garnering this information from the rock record greatly benefits from integrating textural and compositional data with radiometric dating of accessory minerals. Length scales of crystal growth and diffusive transport in accessory minerals under realistic geologic conditions are typically in the range of 1–10’s of μm, and in some cases even substantially smaller, with zircon having among the lowest diffusion coefficients at a given temperature (e.g., Cherniak and Watson 2003). Intrinsic to the compartmentalization of geochemical and geochronologic information from intra-crystal domains is the requirement to determine accessory mineral compositions using techniques that sample at commensurate spatial scales so as to not convolute the geologic signals that are recorded within crystals, as may be the case with single grain or large grain fragment analysis by isotope dilution thermal ionization mass spectrometry (ID-TIMS; e.g., Schaltegger and Davies 2017, this volume; Schoene and Baxter 2017, this volume). Small crystals can also be difficult to extract by mineral separation techniques traditionally used in geochronology, which also lead to a loss of petrographic context. Secondary Ionization Mass Spectrometry, that is SIMS performed with an ion microprobe, is an analytical technique ideally suited to meet the high spatial resolution analysis requirements that are critical for petrochronology (Table 1).\u0000\u0000View this table:\u0000\u0000Table 1 \u0000Advantages and limitations of in-situ SIMS analysis for petrochronology in comparison with other isotope selective methods\u0000\u0000\u0000\u0000In SIMS, bombardment of solid targets with an energetic ion beam removes atoms from the sample where primary ions are implanted into the target material to a depth of < 5–10 nm. Lateral resolution is controlled by primary ion beam dimensions (sub-μm to few 10’s of μm) with an upper limit set by the acceptance …","PeriodicalId":49624,"journal":{"name":"Reviews in Mineralogy & Geochemistry","volume":"418 1","pages":"199-230"},"PeriodicalIF":0.0,"publicationDate":"2017-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79490527","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rutile (TiO2) is an important accessory mineral that, when present, offers a rich source of information about the rock units in which it is incorporated. It occurs in a variety of specific microstructural settings, contains significant amounts of several trace elements and is one of the classical minerals used for U–Pb age determination. Here, we focus on information obtainable from rutile in its original textural context. We do not present an exhaustive review on detrital rutile in clastic sediments, but note that an understanding of the petrochronology of rutile in its source rocks will aid interpretation of data obtained from detrital rutile. For further information on the important role of rutile in provenance studies, the reader is referred to previous reviews (e.g., Zack et al. 2004b; Meinhold 2010; Triebold et al. 2012). Coarse rutile is the only stable TiO2 polymorph under all crustal and upper mantle conditions, with the exception of certain hydrothermal environments (Smith et al. 2009). As such, we will focus on rutile rather than the polymorphs brookite, anatase and ultrahigh-pressure modifications. In this chapter, we first review rutile occurrences, trace element geochemistry, and U–Pb geochronology individually to illustrate the insights that can be gained from microstructures, chemistry and ages. Then, in the spirit of petrochronology, we show the interpretational power of combining these approaches, using the Ivrea Zone (Italy) as a case study. Finally, we suggest some areas of future research that would improve petrochronologic research using rutile. Rutile is a characteristic mineral in moderate- to high pressure metapelitic rocks, in high pressure metamorphosed mafic rocks, and in sedimentary rocks (e.g., Force 1980; Frost 1991; Zack et al. 2004b; Triebold et al. 2012). Rutile also occurs rarely in magmatic rocks, e.g., anorthosites, as well as in some hydrothermal systems. Coarse-grained …
金红石(TiO2)是一种重要的辅助矿物，当它存在时，提供了关于它所包含的岩石单元的丰富信息来源。它存在于各种特定的微观结构环境中，含有大量的几种微量元素，是用于U-Pb年龄测定的经典矿物之一。在这里，我们将重点关注金红石在其原始结构背景下可获得的信息。我们没有对碎屑沉积物中的金红石碎屑进行详尽的回顾，但注意到对其源岩中金红石岩石年代学的理解将有助于解释从金红石碎屑中获得的数据。要进一步了解金红石在种源研究中的重要作用，请参阅以前的综述(例如，Zack等人，2004b;Meinhold 2010;tribold et al. 2012)。除了某些热液环境外，粗金红石是所有地壳和上地幔条件下唯一稳定的TiO2多晶型(Smith et al. 2009)。因此，我们将重点关注金红石，而不是多晶布鲁克石、锐钛矿和超高压改性。在本章中，我们首先分别回顾了金红石的产状、微量元素地球化学和U-Pb年代学，以说明可以从微观结构、化学和年龄中获得的见解。然后，本着岩石年代学的精神，我们展示了结合这些方法的解释能力，并以意大利Ivrea区为例进行了研究。最后，提出了今后利用金红石进行岩石年代学研究的几个方面。金红石是中高压变质岩、高压变质基性岩和沉积岩中的特征矿物(如Force 1980;霜1991;Zack等人，2004b;tribold et al. 2012)。金红石也很少出现在岩浆岩中，例如斜长岩，以及一些热液系统中。粗粒度的……
{"title":"Petrology and Geochronology of Rutile","authors":"T. Zack, E. Kooijman","doi":"10.2138/RMG.2017.83.14","DOIUrl":"https://doi.org/10.2138/RMG.2017.83.14","url":null,"abstract":"Rutile (TiO2) is an important accessory mineral that, when present, offers a rich source of information about the rock units in which it is incorporated. It occurs in a variety of specific microstructural settings, contains significant amounts of several trace elements and is one of the classical minerals used for U–Pb age determination. Here, we focus on information obtainable from rutile in its original textural context. We do not present an exhaustive review on detrital rutile in clastic sediments, but note that an understanding of the petrochronology of rutile in its source rocks will aid interpretation of data obtained from detrital rutile. For further information on the important role of rutile in provenance studies, the reader is referred to previous reviews (e.g., Zack et al. 2004b; Meinhold 2010; Triebold et al. 2012). Coarse rutile is the only stable TiO2 polymorph under all crustal and upper mantle conditions, with the exception of certain hydrothermal environments (Smith et al. 2009). As such, we will focus on rutile rather than the polymorphs brookite, anatase and ultrahigh-pressure modifications.\u0000\u0000In this chapter, we first review rutile occurrences, trace element geochemistry, and U–Pb geochronology individually to illustrate the insights that can be gained from microstructures, chemistry and ages. Then, in the spirit of petrochronology, we show the interpretational power of combining these approaches, using the Ivrea Zone (Italy) as a case study. Finally, we suggest some areas of future research that would improve petrochronologic research using rutile.\u0000\u0000Rutile is a characteristic mineral in moderate- to high pressure metapelitic rocks, in high pressure metamorphosed mafic rocks, and in sedimentary rocks (e.g., Force 1980; Frost 1991; Zack et al. 2004b; Triebold et al. 2012). Rutile also occurs rarely in magmatic rocks, e.g., anorthosites, as well as in some hydrothermal systems. Coarse-grained …","PeriodicalId":49624,"journal":{"name":"Reviews in Mineralogy & Geochemistry","volume":"39 1","pages":"443-467"},"PeriodicalIF":0.0,"publicationDate":"2017-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84391323","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Germanium (Ge) is a trace element in the Earth’s crust and natural waters, averaging about 1.6 ppm in rocks and minerals (El Wardani 1957; Bernstein 1985) and 75 picomol/L in seawater (Froelich and Andreae 1981). The naturally occurring oxidation states of Ge are +2 and +4, with the +4 state forming the principal common and stable compounds. Germanium has outer electronic structure 3 d 10 4 s 2 4 p 2 and mainly occurs in the quadrivalent state, although in some minerals it is octahedrally coordinated. Germanium is chemically similar to silicon (Si), both belonging to the IVA group in the periodic table, with Ge immediately above Si. Germanium is classified as a semimetal, whereas Si is a nonmetal element. Because of nearly identical ionic radii and electron configurations for Ge and Si, the crustal geochemistry of Ge is dominated by a tendency to replace Si in the lattice sites of minerals (Goldschmidt 1958; De Argollo and Schilling 1978b). These two elements exist in seawater as similar hydroxyacids, i.e., Ge(OH)4 and Si(OH)4 (Pokrovski and Schott 1998a) and the concentration profile of Ge is similar to that of Si (Froelich and Andreae 1981), thus making Ge/Si ratio an interesting tracer for biogenic silica cycling in the ocean. Although Ge and Si are geochemically similar, their behavior is different enough so that decoupling of Ge and Si can occur. Germanium commonly occurs in 4-fold (tetrahedral) coordination but in contrast to Si, Ge has a stronger tendency for the 6-fold coordination. Unlike Si, Ge also forms methylated compounds, and high concentrations of monomethyl- and dimethyl-germanium have been detected in ocean waters, accounting for > 70% of the total Ge (Lewis et al. 1985). Germanium is a particularly interesting element for geochemists since it exhibits siderophile, lithophile, chalcophile and …
锗(Ge)是地壳和自然水体中的一种微量元素，在岩石和矿物中的平均含量约为ppm 1.6 (El Wardani 1957;Bernstein 1985)和75皮科莫/升的海水(Froelich和Andreae 1981)。锗的自然氧化态是+2和+4，其中+4形成了主要的常见和稳定的化合物。锗的外电子结构为3d104s24p2，主要以四价态存在，但在某些矿物中为八面体配位。锗在化学上与硅(Si)相似，在元素周期表中都属于IVA族，Ge紧接在Si之上。锗被归类为半金属，而硅是非金属元素。由于Ge和Si的离子半径和电子构型几乎相同，Ge的地壳地球化学倾向于取代矿物晶格位置上的Si (Goldschmidt 1958;De Argollo and Schilling 1978b)。这两种元素在海水中以类似的羟基酸形式存在，即Ge(OH)4和Si(OH)4 (Pokrovski and Schott 1998a)， Ge的浓度分布与Si的相似(Froelich and Andreae 1981)，因此Ge/Si比值成为海洋生物源二氧化硅循环的有趣示踪剂。虽然Ge和Si在地球化学上是相似的，但它们的行为是不同的，因此Ge和Si可以发生解耦。锗通常以四重配位(四面体)存在，但与Si相比，Ge具有更强的六重配位倾向。与硅不同，锗也形成甲基化化合物，在海水中检测到高浓度的单甲基锗和二甲基锗，占锗总量的70%以上(Lewis et al. 1985)。对地球化学家来说，锗是一种特别有趣的元素，因为它具有亲铁、亲石、亲铜和…
{"title":"Germanium Isotope Geochemistry","authors":"O. Rouxel, B. Luais","doi":"10.2138/RMG.2017.82.14","DOIUrl":"https://doi.org/10.2138/RMG.2017.82.14","url":null,"abstract":"Germanium (Ge) is a trace element in the Earth’s crust and natural waters, averaging about 1.6 ppm in rocks and minerals (El Wardani 1957; Bernstein 1985) and 75 picomol/L in seawater (Froelich and Andreae 1981). The naturally occurring oxidation states of Ge are +2 and +4, with the +4 state forming the principal common and stable compounds. Germanium has outer electronic structure 3 d 10 4 s 2 4 p 2 and mainly occurs in the quadrivalent state, although in some minerals it is octahedrally coordinated. Germanium is chemically similar to silicon (Si), both belonging to the IVA group in the periodic table, with Ge immediately above Si. Germanium is classified as a semimetal, whereas Si is a nonmetal element. Because of nearly identical ionic radii and electron configurations for Ge and Si, the crustal geochemistry of Ge is dominated by a tendency to replace Si in the lattice sites of minerals (Goldschmidt 1958; De Argollo and Schilling 1978b). These two elements exist in seawater as similar hydroxyacids, i.e., Ge(OH)4 and Si(OH)4 (Pokrovski and Schott 1998a) and the concentration profile of Ge is similar to that of Si (Froelich and Andreae 1981), thus making Ge/Si ratio an interesting tracer for biogenic silica cycling in the ocean. Although Ge and Si are geochemically similar, their behavior is different enough so that decoupling of Ge and Si can occur. Germanium commonly occurs in 4-fold (tetrahedral) coordination but in contrast to Si, Ge has a stronger tendency for the 6-fold coordination. Unlike Si, Ge also forms methylated compounds, and high concentrations of monomethyl- and dimethyl-germanium have been detected in ocean waters, accounting for > 70% of the total Ge (Lewis et al. 1985). Germanium is a particularly interesting element for geochemists since it exhibits siderophile, lithophile, chalcophile and …","PeriodicalId":49624,"journal":{"name":"Reviews in Mineralogy & Geochemistry","volume":"139 1","pages":"601-656"},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76582172","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Natural variations in the isotopic composition of some 50 chemical elements are now being used in geochemistry for studying transport processes, estimating temperature, reconstructing ocean chemistry, identifying biological signatures, and classifying planets and meteorites. Within the past decade, there has been growing interest in measuring isotopic variations in a wider variety of elements, and improved techniques make it possible to measure very small effects. Many of the observations have raised questions concerning when and where the attainment of equilibrium is a valid assumption. In situations where the distribution of isotopes within and among phases is not representative of the equilibrium distribution, the isotopic compositions can be used to access information on mechanisms of chemical reactions and rates of geological processes. In a general sense, the fractionation of stable isotopes between any two phases, or between any two compounds within a phase, can be ascribed to some combination of the mass dependence of thermodynamic (equilibrium) partition coefficients, the mass dependence of diffusion coefficients, and the mass dependence of reaction rate constants. Many documentations of kinetic isotope effects (KIEs), and their practical applications, are described in this volume and are therefore not reviewed here. Instead, the focus of this chapter is on the measurement and interpretation of mass dependent diffusivities and reactivities, and how these parameters are implemented in models of crystal growth within a fluid phase. There are, of course, processes aside from crystal growth that give rise to KIEs among non-traditional isotopes, such as evaporation (Young et al. 2002; Knight et al. 2009; Richter et al. 2009a), vapor exsolution (Aubaud et al. 2004), thermal diffusion (Richter et al. 2009a, 2014b; Huang et al. 2010; Dominguez et al. 2011), mineral dissolution (e.g., Brantley et al. 2004; Wall et al. 2011; Pearce et al. 2012 …
大约50种化学元素的同位素组成的自然变化现在被用于地球化学，用于研究运输过程、估计温度、重建海洋化学、识别生物特征以及对行星和陨石进行分类。在过去的十年里，人们对测量更多种类元素的同位素变化越来越感兴趣，改进的技术使测量非常小的影响成为可能。许多观察结果提出了关于何时何地达到平衡是一个有效假设的问题。在同位素在相内和相间的分布不能代表平衡分布的情况下，同位素组成可用于获取化学反应机制和地质过程速率的信息。在一般意义上，稳定同位素在任何两相之间，或在一个相内的任何两种化合物之间的分馏，可以归因于热力学(平衡)分配系数的质量依赖性，扩散系数的质量依赖性和反应速率常数的质量依赖性的某种组合。动力学同位素效应(KIEs)的许多文献及其实际应用都在本卷中进行了描述，因此不在这里进行审查。相反，本章的重点是测量和解释质量依赖的扩散率和反应性，以及这些参数如何在流体相中的晶体生长模型中实现。当然，在非传统同位素中，除了晶体生长之外，还有一些过程会产生KIEs，例如蒸发(Young et al. 2002;Knight et al. 2009;Richter et al. 2009a)，蒸汽溶出(Aubaud et al. 2004)，热扩散(Richter et al. 2009a, 2014b;Huang et al. 2010;Dominguez et al. 2011)，矿物溶解(例如，Brantley et al. 2004;Wall et al. 2011;Pearce et al. 2012…
{"title":"Kinetic Fractionation of Non-Traditional Stable Isotopes by Diffusion and Crystal Growth Reactions","authors":"J. Watkins, D. DePaolo, E. Watson","doi":"10.2138/RMG.2017.82.4","DOIUrl":"https://doi.org/10.2138/RMG.2017.82.4","url":null,"abstract":"Natural variations in the isotopic composition of some 50 chemical elements are now being used in geochemistry for studying transport processes, estimating temperature, reconstructing ocean chemistry, identifying biological signatures, and classifying planets and meteorites. Within the past decade, there has been growing interest in measuring isotopic variations in a wider variety of elements, and improved techniques make it possible to measure very small effects. Many of the observations have raised questions concerning when and where the attainment of equilibrium is a valid assumption. In situations where the distribution of isotopes within and among phases is not representative of the equilibrium distribution, the isotopic compositions can be used to access information on mechanisms of chemical reactions and rates of geological processes. In a general sense, the fractionation of stable isotopes between any two phases, or between any two compounds within a phase, can be ascribed to some combination of the mass dependence of thermodynamic (equilibrium) partition coefficients, the mass dependence of diffusion coefficients, and the mass dependence of reaction rate constants. Many documentations of kinetic isotope effects (KIEs), and their practical applications, are described in this volume and are therefore not reviewed here. Instead, the focus of this chapter is on the measurement and interpretation of mass dependent diffusivities and reactivities, and how these parameters are implemented in models of crystal growth within a fluid phase. There are, of course, processes aside from crystal growth that give rise to KIEs among non-traditional isotopes, such as evaporation (Young et al. 2002; Knight et al. 2009; Richter et al. 2009a), vapor exsolution (Aubaud et al. 2004), thermal diffusion (Richter et al. 2009a, 2014b; Huang et al. 2010; Dominguez et al. 2011), mineral dissolution (e.g., Brantley et al. 2004; Wall et al. 2011; Pearce et al. 2012 …","PeriodicalId":49624,"journal":{"name":"Reviews in Mineralogy & Geochemistry","volume":"14 1","pages":"85-125"},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84869964","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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