Mineral chemistry and crystallization conditions of the Late Cretaceous Mamba pluton from the eastern Gangdese, Southern Tibetan Plateau
Mineral chemistry and crystallization conditions of the Late Cretaceous Mamba pluton from the eastern Gangdese, Southern Tibetan Plateau
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藏南冈底斯东部晚白垩世曼巴岩体矿物化学及结晶条件
DOI：
10.1007/s12583-016-0713-5
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发表时间：
2016-06
影响因子：
3.3
通讯作者：
Qi Guan
中科院分区：
文献类型：
--
作者：
Xiaowei Li;Xuanxue Mo;Mark Scheltens;Qi Guan
晚白垩世曼巴花岗闪长岩属于中生代冈底斯大陆岩浆带的一部分。迄今为止，还没有进行定量的矿物学研究，因此它形成的深度受到很大限制。在这里，我们提出的曼巴岩体的矿物学数据，包括寄主岩石和他们的镁铁质微粒包体（MMEs），提供洞察他们的整体结晶条件和岩浆混合的信息。曼巴岩体中角闪石均为钙质，B（Ca+Na）>1.5，寄主岩Si=6.81- 7.42apfu，中微细粒岩体Si=6.77- 7.35apfu。角闪石中主要的阳离子置换类型有浅闪石型和钙霞石型。母岩和MMEs中的黑云母都具有高MgO（13.19wt.% -13.03重量%）含量，但限定了窄范围的Al apfu（每个化学式单元的原子数）变化（2.44-2.57）。氧逸度的估计是基于黑云母组合物集群周围的NNO缓冲区。根据铝合金气压计，计算出的压力范围为1.2至2.1千巴。根据黑云母中的铝气压计，计算的压力在0.9至1.3千巴之间变化，对应于平均深度约为1000千巴。3.9公里.此外，根据Ridolfi等人（2010年）提出的闪石气压计，结晶压力的估计值在0.8至1.4千巴之间，相当于3.1至5.2公里的深度。MMEs有斜长石振荡环带和石英集合体，可能表明岩浆混合的存在。此外，钾长石巨晶的核缘元素（Rb、Sr、Ba和P）的变化也是支持岩浆混合和晶体分异的有力证据。这表明岩浆混合作用对曼巴岩体中钾长石巨晶环带的形成具有重要意义。
The Late Cretaceous Mamba granodiorite belongs to a part of the Mesozoic Gangdese continental magmatic belt. No quantitative mineralogical study has been made hitherto, and hence the depth at which it formed is poorly constrained. Here we present mineralogical data for the Mamba pluton, including host rocks and their mafic microgranular enclaves (MMEs), to provide insights into their overall crystallization conditions and information about magma mixing. All amphiboles in the Mamba pluton are calcic, withB(Ca+Na)>1.5, and Si=6.81–7.42 apfu for the host rocks and Si=6.77–7.35 apfu for the MMEs. The paramount cation substitutions in amphibole include edenite type and tschermakite type. Biotites both in the host rocks and the MMEs collectively have high MgO (13.19 wt.%–13.03 wt.%) contents, but define a narrow range of Al apfu (atoms per formula unit) variations (2.44–2.57). The oxygen fugacity estimates are based on the biotite compositions cluster around the NNO buffer. The calculated pressure ranges from 1.2 to 2.1 kbar according to the aluminum-in-hornblende barometer. The computed pressure varies from 0.9 to 1.3 kbar based on the aluminum-in-biotite barometer which corresponds to an average depth of ca. 3.9 km. Besides, the estimates of crystallization pressures vary from 0.8 to 1.4 kbar based on the amphibole barometer proposed by Ridolfi et al. (2010), which can be equivalent to the depths ranging from 3.1 to 5.2 km. The MMEs have plagioclase oscillatory zonings and quartz aggregates, probably indicating the presence of magma mixing. Besides, core-to-rim element variations (Rb, Sr, Ba, and P) for the K-feldspar megacrysts serve as robust evidence to support magma mixing and crystal fractionation. This indicates the significance of the magma mixing that contributes to the formation of K-feldspar megacryst zonings in the Mamba pluton.
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影响因子：
1.8
作者：
Zhang, Ze-Ming;Dong, Xin;Liu, Feng;Lin, Yan-Hao;Yan, Rong;Santosh, M.
通讯作者：
Santosh, M.
DOI：
10.1086/629570
发表时间：
1992-01
期刊：
The Journal of Geology
影响因子：
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作者：
G. Poli
通讯作者：
G. Poli
DOI：
10.1130/0-8137-2352-3.247
发表时间：
2001
期刊：
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影响因子：
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作者：
R. Ernst;K. Buchan
通讯作者：
R. Ernst;K. Buchan
影响因子：
1.8
作者：
E. Stein;C. Dietl
通讯作者：
E. Stein;C. Dietl
DOI：
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发表时间：
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期刊：
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影响因子：
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作者：
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