Mineralogical evidence for crystallization conditions and petrogenesis of ilmenite-series I-type granitoids at the Baogutu reduced porphyry Cu deposit (Western Junggar, NW China): Mössbauer spectroscopy, EPM and LA-(MC)-ICPMS analyses
Mineralogical evidence for crystallization conditions and petrogenesis of ilmenite-series I-type granitoids at the Baogutu reduced porphyry Cu deposit (Western Junggar, NW China): Mössbauer spectroscopy, EPM and LA-(MC)-ICPMS analyses
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包古图还原斑岩铜矿床（中国西北准噶尔）钛铁矿系列 I 型花岗岩的结晶条件和岩石成因的矿物学证据：穆斯堡尔谱、EPM 和 LA-(MC)-ICPMS 分析
DOI：
10.1016/j.oregeorev.2017.02.033
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发表时间：
2017-06
影响因子：
3.3
通讯作者：
Andreas Kappler
中科院分区：
文献类型：
--
作者：
Mingjian Cao;Kezhang Qin;Guangming Li;Noreen J. Evans;Pete Hollings;Markus Maisch;Andreas Kappler
原生成矿矿物保留了岩浆结晶信息的地球化学特征，并能反映其形成时的岩石化学条件。宝古图存款矿床是典型的还原斑岩型铜存款矿床。角闪石和黑云母Fe 3 +/Fe 3 + Fe比值，矿物利用穆斯堡尔谱学、电子探针显微分析和激光烧蚀多收集电感耦合等离子体质谱法分别测定了岩浆（长石、黑云母、角闪石、锆石和磷灰石）、原位元素和磷灰石Nd同位素组成，探讨了岩浆的氧化状态、岩石成因、源区特征并对侵入期岩浆阶段的碳物种进行了限制。结果表明，成矿闪长-花岗闪长斑岩和成矿后角闪长闪长斑岩中原生斜长石和角闪石明显不同（An 26 - 55与An 60 -69;镁角闪石与绿闪长斑岩）。角闪石具有明显的主、微量元素组成，镁角闪石中轻稀土元素富集，Eu负异常，钙黄长石中轻稀土元素亏损，无Eu异常。所有分析的黑云母都是原生火成岩相，黑云母斑晶剖面显示Zn、Cr、Sc和Sr从核到边缘的显著变化。这些结果可能表明，在矿物形成过程中，两种不同的岩浆之间发生了混合。锆石中的钛和角闪石中的硅含量表明，岩浆结晶温度>900 °C，并持续到650 °C。原位磷灰石Nd同位素（εNd（t）= 5.6-7.6，TDM 2 = 620-460 Ma）表明，没有明显的还原沉积混染，也没有年轻下地壳的来源。从黑云母和角闪石到全岩，Fe ~（3+）/Fe ~（3+）比值略有降低，表明岩浆结晶过程中氧逸度降低。根据Fe ~（3+）/Fe ~（3+）比值重新计算的黑云母成分表明，fO 2值小于Ni-NiO缓冲区（NNO），比根据锆石/熔体分配系数Ce异常估算的值（ΔNNO + 0.6）略低。这些值与还原斑岩铜矿的特征相一致。其他矿物相的结晶显着影响锆石/熔体分配系数的氧气压计的可靠性，Eu异常和磷灰石中的Mn含量。这种氧化态表明，只有CO2存在于岩浆阶段，并意味着CH 4在CO2还原发生后热液蚀变。原生角闪石向阳起石的蚀变释放了Ti、Al、Fe、Mn、Na、K等元素，并在阳起石蚀变过程中沉淀出钛铁矿、钠长石、少量钛铁矿和磁铁矿。
Primary ore-forming minerals retain geochemical signatures of magmatic crystallization information and can reveal the petrochemical conditions prevalent at the time of their formation. The Baogutu deposit is a typical reduced porphyry Cu deposit. Amphibole and biotite Fe3+/ΣFe ratios, minerals (feldspar, biotite, amphibole, zircon and apatite),in situelemental and apatite Nd isotopic compositions were determined by Mössbauer spectroscopy, electron probe microanalysis, and laser ablation multiple-collection inductively coupled plasma mass spectrometry, respectively, to investigate the magma oxidation state, petrogenesis, source features, and to constrain the carbon species at magmatic stages for the intrusive phases. The results show that the primary plagioclase and amphibole in the mineralized diorite to granodiorite porphyry and post ore hornblende diorite porphyry are distinct (An26-55versus An60-69; Mg-hornblende versus tschermakite). In particular, the amphibole shows distinct major and trace element compositions with light rare earth element enrichments and negative Eu anomalies in Mg-hornblende and light rare earth element depletions and no Eu anomalies in tschermakite. All the analyzed biotites are primary igneous phases with a biotite phenocryst profile showing significant variations of Zn, Cr, Sc and Sr from core to rim. These results may indicate the occurrence of mixing between two distinct magmas during mineral formation. Titanium in zircon and Si∗in amphibole thermometries indicate that magma crystallized at >900 °C and continued to ∼650 °C.In situapatite Nd isotope (εNd(t) = 5.6–7.6, TDM2= 620–460 Ma), indicate absence of significant reduced sedimentary contamination and the source of juvenile lower crust. Slightly decreasing Fe3+/ΣFe ratios from biotite and amphibole to whole rock indicate decreasing oxygen fugacity during magma crystallization. Recalculated biotite compositions according to Fe3+/ΣFe ratios indicatefO2values of less than Ni-NiO buffer (NNO) which show slightly lower values than that estimated according to zircon/melt distribution coefficients Ce anomalies (∼ΔNNO + 0.6). These values are consistent with the features of reduced porphyry Cu deposits. Crystallization of other mineral phases significantly affects the reliability of oxybarometer of zircon/melt distribution coefficients Eu anomalies and Mn contents in apatite. This oxidation state suggests that only CO2was present at the magmatic stage, and implies that CH4formed during CO2reduction occurring later hydrothermal alteration. The alteration of primary amphibole to actinolite released Ti, Al, Fe, Mn, Na and K to the fluid with later precipitation of titanite, albite and minor ilmenite and magnetite during actinolite alteration.
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影响因子：
3.9
作者：
Cherniak, DJ;Hanchar, JM;Watson, EB
通讯作者：
Watson, EB
影响因子：
2.9
作者：
Mingjian Cao;Guangming Li;K. Qin;N. Evans;E. Seitmuratova
通讯作者：
Mingjian Cao;Guangming Li;K. Qin;N. Evans;E. Seitmuratova
影响因子：
1.4
作者：
L. Aldridge;J. Finch;G. Gainsford;K. H. Patterson;W. Tennant
通讯作者：
L. Aldridge;J. Finch;G. Gainsford;K. H. Patterson;W. Tennant
影响因子：
5.8
作者：
T. Takagi;K. Tsukimura
通讯作者：
T. Takagi;K. Tsukimura
DOI：
10.1088/0031-9112/7/10/004
发表时间：
2011-09
期刊：
Physics Bulletin
影响因子：
--
作者：
W. Ni
通讯作者：
W. Ni