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Bouchra Baidada Abdelkhalek Alansari Basem Zoheir Said Ilmen Abderrahmane Soulaimani Moha Ikenne 《Chemie der Erde / Geochemistry》2018,78(4):462-478
The Imiter inlier at the eastern Anti-Atlas chain (Morocco) hosts a world-class epithermal Ag-Hg deposit, and several occurrences of sulfide-magnetite mineralization. These occurrences are confined to transcurrent faults that cut mildly to highly potassic I- and S-type granite intrusions (e.g., Igoudrane, Bou Teglimt, Taouzzakt and Bou Fliou).In this contribution, we present new field, petrographic and microanalytical data of the Bou Fliou sulfide-magnetite mineralization in the northwestern part of the Bou Teglimt granodiorite intrusion (567?±?6Ma). Field and microscopic investigations reveal pervasive silicification and potassic alteration associated with iron oxides-rich (>10?vol %) veins, stockworks, and breccias along NE-SW faults. The ore minerals are mainly magnetite, hematite, chalcopyrite, pyrite, sphalerite, Ag-galena, cobaltite, and less abundant Bi-sulfosalts (i.e., cosalite, galenobistmuthite, and llilanite-gustavite). The low-titanium iron oxides (magnetite and hematite), widespread iron-rich breccia, association with crustal scale fault zone, pervasive alteration, and overprinting mineral assemblages suggest a shallow level IOCG-style mineralization. High-order splays of the major fault zone could have provided effective traps for magmatic and basinal Cu and Zn-Pb hydrothermal fluids. The ～550 Ma intrusive phases in the region could have contributed by fluid, elements or heat in a local effective blumbing. The mineralogical and ore textural criteria reflecting ore formation at a realtively shallow crustal environment, but a fluid inclusion study is needed to characterize the ore fluids and mechanism of ore deposition. 相似文献
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本文对湘南宝山花岗闪长斑岩进行了系统的锆石和磷灰石U-Pb定年、岩石地球化学以及锆石Hf同位素研究,并探讨了宝山花岗闪长斑岩的岩石成因和构造意义。锆石和磷灰石的LA-ICP-MS U-Pb定年显示,宝山花岗闪长斑岩的成岩年龄为160Ma。综合元素和同位素地球化学证据,宝山花岗闪长斑岩的成因可能为新生地壳与古老地壳的混合熔融,同时宝山花岗闪长斑岩中发现的890±20Ma的继承锆石,验证了新元古代新生地壳的参与。磷灰石的主微量元素研究显示花岗闪长斑岩具有较高的氧逸度和Cl含量,Sr/Th比值具有较大变化,而La/Sm比值变化不大等特征,表明形成花岗闪长斑岩岩浆的母岩受到俯冲板片脱水形成的流体交代作用影响。在上述过程中,富含Cl和H2O的流体从板片中释放出来,引发地幔楔熔融,并对矿床中成矿金属元素进行提取。由于古太平洋板块俯冲引发的伸展-减薄运动,在地幔上涌过程中,新元古代新生地壳发生部分熔融,这些高温岩浆底侵老地壳源区,诱发老地壳部分熔融,进而发生了强烈的壳-壳混合作用,产生花岗闪长质岩浆。 相似文献
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Porphyry and skarn Cu–Fe–Au–Mo deposits are widespread in the Middle and Lower Yangtze River metallogenic belt (MLYMB), eastern China. The Matou deposit has long been regarded as a typical Cu–Mo porphyry deposit within Lower Yangtze part of the belt. Recently, we identified scheelite and wolframite in quartz veins in the Matou deposit, which is uncommon in other porphyry and skarn deposits in the MLYMB. We carried out detailed zircon U–Pb dating and geochemical and Sr–Nd–Hf isotopic studies of the granodiorite porphyry at Matou to define any differences from other ore-related granitoids. The porphyry shows a SiO2 content ranging from 61.85 wt.% to 65.74 wt.%, K2O from 1.99 wt.% to 3.74 wt.%, and MgO from 1.74 wt.% to 2.19 wt.% (Mg# value ranging from 45 to 55). It is enriched in light rare earth elements and large ion lithophile elements, but relatively depleted in Nb, Ta, Y, Yb and compatible trace elements (such as Cr, Ni, and V), with slight negative Eu anomalies (Eu/Eu* = 0.88–0.98) and almost no negative Sr anomalies. Results of electron microprobe analysis of rock-forming silicate minerals indicate that the Matou porphyry has been altered by an oxidized fluid that is rich in Mg, Cl, and K. The samples show relatively low εNd(t) values from −7.4 to −7.1, slightly high initial 87Sr/86Sr values from 0.708223 to 0.709088, and low εHf(t) values of zircon from −9.0 to −6.5, when compared with the other Cu–Mo porphyry deposits in the MLYMB. Zircon U–Pb dating suggests the Matou granodiorite porphyry was emplaced at 139.5 ± 1.5 Ma (MSWD = 1.8, n = 15), which is within the age range of the other porphyries in the MLYMB. Although geochemical characteristics of the Matou and other porphyries in the MLYMB are similar and all adakitic, the detrital zircons in the samples from Matou suggest that Archean lower crust (2543 ± 29 Ma, MSWD = 0.25, n = 5) was involved with the generation of Matou magma, which is different from the other porphyries in the belt. Our study suggests that the Matou granodiorite porphyry originated from partial melting of thickened lower crust that was delaminated into the mantle, similar to the other porphyries in the MLYMB, but it has a higher proportion of lower crustal material, including Archean rocks, which contributed to the formation of the porphyry and related W-rich magmatic-hydrothermal system. 相似文献
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皖南晚中生代花岗闪长岩地球化学:成岩成矿制约 总被引：3，自引：2，他引：1
皖南地区是铜、钼、金多金属成矿区,成矿与晚中生代花岗闪长岩类关系密切。近十年来,皖南花岗闪长岩的成因仍然存在分歧。本次报道了皖南花岗闪长岩全岩主、微量元素和锆石原位元素数据。皖南花岗闪长岩(Si O2=64.3%~70.8%)为高钾钙碱性、过铝质岩石,具有相似的埃达克岩特征:高Si O2、Sr/Y(17.1)和(La/Yb)N(14.9)比值,低Yb(1.72×10-6)和Y(18.4×10-6)含量。它们也具有较低Al2O3和Cr(3.40×10-6~10.0×10-6)含量、低Mg#(0.34~0.42)和Nb/Ta(9.6~13.3)值,高K2O和Ba(404×10-6)含量,高K2O/Na2O(0.89~1.55)、Th/La(0.27~0.51)和Th/U(2.79~7.49)比值。锆石原位地球化学特征显示其岩浆源区为低温(锆石Ti-in-zircon温度均值674℃)和高氧逸度(lgfO2集中在-21.4~-9.18,均值-16.4;锆石Ce4+/Ce3+平均值276)的陆壳。这些特征说明皖南花岗闪长岩可能起源于较年轻的加厚下地壳的部分熔融,并经历了斜长石、钾长石和铁镁矿物等结晶分异作用。它们可能形成于与古太平洋板块俯冲密切相关的大陆活动边缘弧至弧后拉张构造转换背景。本区大规模Cu、Mo、Au成矿作用与岩浆的高氧逸度密切相关,而锆石Ce4+/Ce3+可作为矿床勘探一个有效的指标。 相似文献
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村前铜多金属矿床位于钦杭成矿带东段,为一具有矽卡岩型矿化和斑岩型矿化的铜多金属矿床,含矿岩体为燕山早期花岗闪长斑岩,岩石具有富硅、富铝、富碱的特点,属于偏铝-过铝质钙碱性花岗岩类。岩体具有从深部向浅部蚀变增强,大部分组分活动性不明显,而成矿元素Cu-Mo-Fe-Pb-Zn-Au-Ag含量明显增加,Na2O、Sr含量降低,REE元素除Eu少量丢失外,其余均呈一致的迁入特征。岩体属Ⅰ型花岗质岩石,由具角闪石+石榴子石残留相的火成岩部分熔融形成的熔浆,混合或混染了地壳重熔型岩浆上侵就位而成。钦杭结合带东段,燕山期中酸性岩浆活动具有从176~150Ma的埃达克岩或具岛弧花岗岩特征的Ⅰ型花岗岩,至150~140Ma的S型花岗岩,向140~110Ma的A型花岗岩演化趋势,显示了地壳由厚减薄的过程,暗示其大地构造背景为岩石圈的伸展减薄环境,而形成于169.3±1.1Ma的村前斑岩体正处于伸展阶段早期。综合岩体成矿特征表明,钦杭成矿带东段及邻近地区,176~160Ma主要形成与Ⅰ型花岗质岩石有关的以Cu为主的多金属矿床;160~150Ma主要形成与Ⅰ型花岗质岩石有关的Cu-Mo矿床与W-Sn矿床;150~140Ma主要形成与S型花岗质岩石有关的以W-Sn-Mo为主的多金属矿床,以及以Ag-Pb-Zn为主的多金属矿床;140~110Ma主要形成与A型花岗质岩石有关的以W-Sn-Mo为主的多金属矿床,少量与Ⅰ型花岗质岩石有关的Pb-Zn矿床。 相似文献
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P. D. Katsabanis A. Tawadrous C. Braun C. Kennedy 《Fragblast: International Journal for Blasting and Fragmentation》2006,10(1):83-93
A series of small scale tests, simulating multi-hole blasts have been performed to establish the effect of delays on blast fragmentation. The blasts were performed in high quality granodiorite blocks, which were cut from stone prepared by dimensional stone quarry operations. The pattern used was equilateral triangular, with a distance of 10.2 cm between boreholes, which had a diameter of 11 mm, were loaded with detonating cord and the coupling medium was water. The delays used were achieved using different lengths of detonating cord for the cases of delays between 0 and 100 μs between holes and a sequential blasting machine firing seismic detonators for larger delays up to 4 ms. All fragments were collected and screened. The experiments showed that the worst fragmentation was achieved with simultaneous initiation of all charges. Fragmentation improved with the delay time between holes up to 1 ms between holes. If the experiments are scaled up, the results show that in granodiorite, fragmentation optimization requires delays of few milliseconds per metre of burden. The findings, agree with previously published work, involving larger scale experiments and other rock types. 相似文献
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Masatoshi Bando Greg Bignall Kotaro Sekine Noriyoshi Tsuchiya 《Journal of Volcanology and Geothermal Research》2003,120(3-4):215-234
The Quaternary Takidani Granodiorite (Japan Alps) is analogous to the type of deep-seated (3–5 km deep) intrusive-hosted fracture network system that might support (supercritical) hot dry/wet rock (HDR/HWR) energy extraction. The I-type Takidani Granodiorite comprises: porphyritic granodiorite, porphyritic granite, biotite-hornblende granodiorite, hornblende-biotite granodiorite, biotite-hornblende granite and biotite granite facies; the intrusion has a reverse chemical zonation, characterized by >70 wt% SiO2 at its inferred margin and <67 wt% SiO2 at the core. Fluid inclusion evidence indicates that fractured Takidani Granodiorite at one time hosted a liquid-dominated, convective hydrothermal system, with <380°C, low-salinity reservoir fluids at hydrostatic (mesothermal) pressure conditions. ‘Healed’ microfractures also trapped >600°C, hypersaline (35 wt% NaCleq) fluids of magmatic origin, with inferred minimum pressures of formation being 600–750 bar, which corresponds to fluid entrapment at 2.4–3.0 km depth. Al-in-hornblende geobarometry indicates that hornblende crystallization occurred at about 1.45 Ma (7.7–9.4 km depth) in the (marginal) eastern Takidani Granodiorite, but later (at 1.25 Ma) and shallower (6.5–7.0 km) near the core of the intrusion. The average rate of uplift across the Takidani Granodiorite from the time of hornblende crystallization has been 5.1–5.9 mm/yr (although uplift was about 7.5 mm/yr prior to 1.2 Ma), which is faster than average uplift rates in the Japan Alps (3 mm/yr during the last 2 million years). A temperature–depth–time window, when the Takidani Granodiorite had potential to host an HDR system, would have been when the internal temperature of the intrusive was cooling from 500°C to 400°C. Taking into account the initial (7.5 mm/yr) rate of uplift and effects of erosion, an optimal temperature–time–depth window is proposed: for 500°C at 1.54–1.57 Ma and 5.2±0.9 km (drilling) depth; and 400°C at 1.36–1.38 Ma and 3.3±0.8 km (drilling) depth, which is within the capabilities of modern drilling technologies, and similar to measured temperature–depth profiles in other active hydrothermal systems (e.g. at Kakkonda, Japan). 相似文献
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西藏弄如日金矿床花岗斑岩年代学与岩石成因 总被引：1，自引：1，他引：0
弄如日矿区发育中新世浅成花岗闪长斑岩和二长花岗斑岩两类岩体,本文对这两类花岗斑岩体进行了LA-ICPMS锆石U-Pb定年和系统的岩体地质、岩石学和元素地球化学研究。结果显示,花岗闪长斑岩和二长花岗斑岩近于同期侵入,前者为未分异或弱分异花岗岩,后者为高分异花岗岩。花岗闪长斑岩和二长花岗斑岩的侵位年龄测试结果表明,前者形成时代为20. 3±0. 8Ma,后者形成于20. 20±0. 41Ma～20. 51±0. 52Ma。花岗闪长斑岩具有低硅、低钾、低碱、高铝的特点,SiO_2介于63. 37%～66. 78%之间,Al2O3变化于15. 14%～16. 04%,Na_2O+K_2O=4. 46%～5. 33%,A/CNK=1. 13～1. 26,稀土总量高,重稀土和Y含量低,具有埃达克质岩石的地球化学特点,主体为Ⅰ型花岗岩。二长花岗斑岩具有高硅、高钾、高碱、低铝、稀土总量低的特点,SiO_2=70. 46%～77. 17%,Al_2O_3=12. 22%～15. 06%,Na_2O+K_2O=7. 14%～7. 98%,A/CNK=1. 03～1. 21,稀土总量低,为Ⅰ型花岗岩。两种岩石稀土元素分配典线呈右倾型,均富集大离子亲石元素(Rb、Ba等),亏损高场强元素(Nb、Ta、Zr);此外,花岗闪长斑岩轻重稀土分馏明显,而二长花岗斑岩中稀土和重稀土分馏不明显。花岗闪长斑岩形成于弄如日矿区加厚下地壳中变基性岩的部分熔融,变基性岩很可能是榴辉岩(可能含有角闪石),部分熔融后的残留物以石榴石为主,含金红石。二长花岗斑岩可能是由花岗闪长斑岩浆通过分离结晶衍生而来,分离结晶的矿物包括斜长石、黑云母、钾长石、钛铁矿、榍石、磷灰石等。综合研究表明,弄如日金矿成矿时代略晚于花岗闪长斑岩侵位,成矿与花岗闪长斑岩及其分异的二长花岗斑岩关系密切。花岗闪长斑岩及二长花岗斑岩的侵位时代及成因研究,对揭示弄如日金矿矿床成因有重要意义,也为区域寻找该类矿床指明了方向。 相似文献