Decoupled whole-rock and zircon Hf isotopes in young evolved post-collisional lavas from Dayingshan (SE Tibet): Evidence for open-system magmatic processes

Lithos ◽  
2021 ◽  
pp. 106393
Author(s):  
Zipei Guo ◽  
Haibo Zou
Keyword(s):  
Open System ◽  
Hf Isotopes ◽  
Magmatic Processes ◽  
Se Tibet

Combining Nd isotopes in monazite and Hf isotopes in zircon to understand complex open-system processes in granitic magmas

Geology ◽  
2017 ◽  
Vol 45 (3) ◽  
pp. 267-270 ◽  
Author(s):  
Christopher M. Fisher ◽  
John M. Hanchar ◽  
Calvin F. Miller ◽  
Stacy Phillips ◽  
Jeffrey D. Vervoort ◽  
...  
Keyword(s):  
Open System ◽  
Hf Isotopes ◽  
Nd Isotopes

scholarly journals Petrogenesis of the Nashwaak Granite, West-Central New Brunswick, Canada: Evidence from Trace Elements, O and Hf Isotopes of Zircon, and O Isotopes of Quartz

Minerals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 614 ◽  
Author(s):  
Wei Zhang ◽  
David R. Lentz ◽  
Kathleen G. Thorne
Keyword(s):  
Trace Elements ◽  
New Brunswick ◽  
Open System ◽  
Biotite Granite ◽  
Hf Isotopes ◽  
Magmatic Zircon ◽  
Basement Rocks ◽  
O Isotopes ◽  
Isotopic Disequilibrium

The petrogenesis of the Pridoli to Early Lochkovian granites in the Miramichi Highlands of New Brunswick, Canada, is controversial. This study focuses on the Pridoli Nashwaak Granite (biotite granite and two-mica granite). In situ trace elements and O and Hf isotopes in zircon, coupled with O isotopes in quartz, are used to reveal its magmatic sources and evolution processes. In the biotite granite, inherited zircon cores have broadly homogenous δ18OZrc ranging from +6.7‰ to 7.4‰, whereas magmatic zircon rims have δ18OZrc of +6.3‰ to 7.2‰ and εHf(t) of −0.39 to −5.10. The Hf and Yb/Gd increase with decreasing Th/U. Quartz is isotopically equilibrated with magmatic zircon rims. The biotite granite is interpreted to be solely derived by partial melting of old basement rocks of Ganderia and fractionally crystallized at the fO2 of 10−21 to 10−10 bars. The two-mica granite has heterogeneous inherited zircon cores (δ18OZrc of +5.2‰ to 9.9‰) and rims (δ18OZrc of +6.2‰ to 8.7‰), and εHf(t) of −11.7 to −1.01. The two-mica granite was derived from the same basement, but with supracrustal contamination. This open-system process is also recorded by Yb/Gd and Th/U ratios in zircon and isotopic disequilibrium between magmatic zircon rims and quartz (+10.3 ± 0.2‰).

THE NEAR-UBIQUITY OF OPEN-SYSTEM MAGMATIC PROCESSES

2017 ◽  
Author(s):  
Michael A. Dungan ◽  
Keyword(s):  
Open System ◽  
Magmatic Processes

scholarly journals Diagnosing open-system magmatic processes using the Magma Chamber Simulator (MCS): part I—major elements and phase equilibria

2020 ◽  
Vol 175 (11) ◽  
Author(s):  
Wendy A. Bohrson ◽  
Frank J. Spera ◽  
Jussi S. Heinonen ◽  
Guy A. Brown ◽  
Melissa A. Scruggs ◽  
...  
Keyword(s):  
Phase Equilibria ◽  
Magma Chamber ◽  
Open System ◽  
Major Elements ◽  
Magmatic Processes

scholarly journals Diagnosing open-system magmatic processes using the Magma Chamber Simulator (MCS): part II—trace elements and isotopes

2020 ◽  
Vol 175 (11) ◽  
Author(s):  
Jussi S. Heinonen ◽  
Wendy A. Bohrson ◽  
Frank J. Spera ◽  
Guy A. Brown ◽  
Melissa A. Scruggs ◽  
...  
Keyword(s):  
Trace Elements ◽  
Phase Equilibria ◽  
Trace Element ◽  
Magma Chamber ◽  
Open System ◽  
Companion Paper ◽  
Compositional Evolution ◽  
Element Concentrations ◽  
Element Partitioning ◽  
Magmatic Processes

Abstract The Magma Chamber Simulator (MCS) is a thermodynamic model that computes the phase, thermal, and compositional evolution of a multiphase–multicomponent system of a Fractionally Crystallizing resident body of magma (i.e., melt ± solids ± fluid), linked wallrock that may either be assimilated as Anatectic melts or wholesale as Stoped blocks, and multiple Recharge reservoirs (RnASnFC system, where n is the number of user-selected recharge events). MCS calculations occur in two stages; the first utilizes mass and energy balance to produce thermodynamically constrained major element and phase equilibria information for an RnASnFC system; this tool is informally called MCS-PhaseEQ, and is described in a companion paper (Bohrson et al. 2020). The second stage of modeling, called MCS-Traces, calculates the RASFC evolution of up to 48 trace elements and seven radiogenic and one stable isotopic system (Sr, Nd, Hf, 3xPb, Os, and O) for the resident melt. In addition, trace element concentrations are calculated for bulk residual wallrock and each solid (± fluid) phase in the cumulate reservoir and residual wallrock. Input consists of (1) initial trace element concentrations and isotope ratios for the parental melt, wallrock, and recharge magmas/stoped wallrock blocks and (2) solid-melt and solid–fluid partition coefficients (optional temperature-dependence) for stable phases in the resident magma and residual wallrock. Output can be easily read and processed from tabulated worksheets. We provide trace element and isotopic results for the same example cases (FC, R2FC, AFC, S2FC, and R2AFC) presented in the companion paper. These simulations show that recharge processes can be difficult to recognize based on trace element data alone unless there is an independent reference frame of successive recharge events or if serial recharge magmas are sufficiently distinct in composition relative to the parental magma or magmas on the fractionation trend. In contrast, assimilation of wallrock is likely to have a notable effect on incompatible trace element and isotopic compositions of the contaminated resident melt. The magnitude of these effects depends on several factors incorporated into both stages of MCS calculations (e.g., phase equilibria, trace element partitioning, style of assimilation, and geochemistry of the starting materials). Significantly, the effects of assimilation can be counterintuitive and very different from simple scenarios (e.g., bulk mixing of magma and wallrock) that do not take account phase equilibria. Considerable caution should be practiced in ruling out potential assimilation scenarios in natural systems based upon simple geochemical “rules of thumb”. The lack of simplistic responses to open-system processes underscores the need for thermodynamical RASFC models that take into account mass and energy conservation. MCS-Traces provides an unprecedented and detailed framework for utilizing thermodynamic constraints and element partitioning to document trace element and isotopic evolution of igneous systems. Continued development of the Magma Chamber Simulator will focus on easier accessibility and additional capabilities that will allow the tool to better reproduce the documented natural complexities of open-system magmatic processes.

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