Evidence of a mantle contribution in the genesis of magmatic rocks from the Neogene Batu Hijau district in the Sunda Arc, South Western Sumbawa, Indonesia

Fiorentini, Marco L.; Garwin, Steve

doi:10.1007/s00410-009-0457-7

Cited by 26 publications

(10 citation statements)

References 67 publications

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“…This apparent lack of crustal contamination is consistent with the juvenile isotopic signatures (Pb-Pb, Sm-Nd, Rb-Sr) of intrusions in the Batu Hijau district (Garwin, 2000;Fiorentini and Garwin, 2010). The juvenile and "porphyry-fertile" magmas at Batu Hijau have been explained by asthenospheric mantle upwelling through a tear in the subducting slab that resulted from the collision with the Roo rise (Garwin, 2000;Fiorentini and Garwin, 2010). This would also explain why the only mined porphyry-deposit in the Sunda-Banda arc (Batu Hijau) and the most promising prospects (Elang and Tumpangpitu) are located above the inferred margin of the subducting Roo rise (Fig.…”

Section: Resolving Lower Crustal Magmatic Processes From Zircon Petrosupporting

confidence: 81%

“…Tapster et al, 2016;Lee et al, 2017;Large et al, 2018), which have been interpreted to represent extended interaction with arc lithologies (Miller et al, 2007). This apparent lack of crustal contamination is consistent with the juvenile isotopic signatures (Pb-Pb, Sm-Nd, Rb-Sr) of intrusions in the Batu Hijau district (Garwin, 2000;Fiorentini and Garwin, 2010). The juvenile and "porphyry-fertile" magmas at Batu Hijau have been explained by asthenospheric mantle upwelling through a tear in the subducting slab that resulted from the collision with the Roo rise (Garwin, 2000;Fiorentini and Garwin, 2010).…”

Section: Resolving Lower Crustal Magmatic Processes From Zircon Petrosupporting

confidence: 61%

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Resolving the timescales of magmatic and hydrothermal processes associated with porphyry deposit formation using zircon U-Pb petrochronology

Large¹,

Wotzlaw²,

Guillong³

et al. 2020

Preprint

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Abstract. Understanding the formation of economically important porphyry-Cu-Au deposits requires the knowledge of the magmatic-to-hydrothermal processes that act within the much larger underlying magmatic system and the timescales on which they occur. We apply high-precision zircon geochronology (CA-ID-TIMS) and spatially resolved zircon geochemistry (LA-ICP-MS) to constrain the magmatic evolution of the magma reservoir at the Pliocene Batu Hijau porphyry-Cu-Au deposit. We then use this extensive dataset to assess the accuracy and precision of different U-Pb dating methods of the same zircon crystals. Emplacement of the oldest pre- to syn-ore tonalite (3.736 &#177; 0.023&#8201;Ma) and the youngest tonalite porphyry cutting economic Cu-Au mineralisation (3.646 &#177; 0.022&#8201;Ma) is determined by the youngest zircon grain from each sample, which constrains the duration of metal precipitation to less than 90 &#177; 32&#8201;kyr. Overlapping spectra of single zircon crystallisation ages and their trace element distributions from the pre-, syn and post-ore tonalite porphyries reveal protracted zircon crystallisation together with apatite and plagioclase within the same magma reservoir over >&#8201;300&#8201;kyr. The presented petrochronological data constrains a protracted early >&#8201;200&#8201;kyr interval of melt differentiation and cooling within a large heterogeneous magma reservoir leading up to ore formation, followed by magma storage in a highly crystalline state and chemical and thermal stability over several 10s of kyr. Irregular trace element systematics suggest magma recharge or underplating during this final short time interval. The comparison of high precision CA-ID-TIMS results with in-situ U-Pb geochronology data from the same zircon grains allows a comparison of the applicability of each technique as a tool to constrain dates and rates on different geological timescales. All techniques provide accurate dates with variable precision. Highly precise dates derived by the calculation of the weighted mean and standard error of the mean of zircon dates obtained by in-situ techniques can lead to significantly older suggested emplacement ages than those determined by high-precision CA-ID-TIMS geochronology. This lack in accuracy of the weighted means is due to the protracted nature of zircon crystallisation in upper crustal magma reservoirs, suggesting that standard errors should not be used as a mean to describe the uncertainty in those circumstances. Thus, geologically rapid events or processes or the tempo of magma evolution are too fast to be reliably resolved by in-situ U-Pb geochronology and require ID-TIMS geochronology.

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Section: Resolving Lower Crustal Magmatic Processes From Zircon Petrosupporting

confidence: 81%

Section: Resolving Lower Crustal Magmatic Processes From Zircon Petrosupporting

confidence: 61%

Resolving the timescales of magmatic and hydrothermal processes associated with porphyry deposit formation using zircon U-Pb petrochronology

Large¹,

Wotzlaw²,

Guillong³

et al. 2020

Preprint

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“…Magma alkalinity increases in the young volcanoes, and towards the back arc. The arc demonstrates several distinctive features that differ from the idealized temporal and spatial schemes of subduction zone magmatism (Foden and Varne, 1980;Soeria-Atmadja et al, 1994;Setijadji et al, 2006;Fiorentini and Garwin, 2009). The eastern Sunda Arc underwent migrations towards the hinterland during its Cenozoic history, which is different from a typical foreland migration of a subduction zone (Setijadji et al, 2006).…”

Section: Regional Geologymentioning

confidence: 90%

“…Subduction along the eastern Sunda -Banda Arc initiated in the Paleocene-Eocene, and the arc underwent a period of extension related to slab rollback around 15 -12 Ma (Hall, 2002;Smyth et al, 2005;Fiorentini and Garwin, 2009;Spakman and Hall, 2010). This initiated a polarity shift to southward-directed subduction of oceanic crust of the marginal Banda Sea beneath the arc (Fiorentini and Garwin, 2009). Complexities arose in the Miocene due to the subduction of the Roo Rise, a trapped slab of thickened oceanic crust (Fig.…”

Section: Regional Tectonicsmentioning

confidence: 99%

Tectonics and Geology of Porphyry Cu-Au Deposits along the Eastern Sunda Magmatic Arc, Indonesia

et al. 2018

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The discovery of the world class copper-gold deposit at Tumpangpitu, East Java (1.9 Gt @ 0.45% Cu, 0.45 g/t Au), has reinforced the eastern Sunda Arc as a significant metallogenic belt, highly prospective for the discovery of major porphyry deposits. The arc hosts three premier porphyry copper-gold deposits at Batu Hijau, Elang, and Tumpangpitu (>300 t Au and >5 Mt Cu). These giant porphyry deposits are confined to the eastern segment of the eastern Sunda Arc (eastern Java to Sumbawa), constructed on island arc crust where the Roo Rise is being subducted. By contrast, major epithermal (low-sulfidation dominant) deposits associated with poorly-endowed porphyry prospects occur along the western segment of the arc (western Java), developed on thick continental crust on the southern margin of Sundaland associated with subduction of typically thin Indian oceanic crust.Porphyry copper-gold deposits of the eastern-Sunda Arc are spatially associated with small, nested, dioritic to tonalitic intrusive complexes with low-K calc-alkaline to weakly alkaline signatures.Hypogene alteration and mineralization developed during three main temporally and spatially overlapping events, termed early, transitional and late. The hypogene copper-gold mineralized zone of the giant deposits forms a bell-shaped body of 0.3% Cu shell greater than 1 km in both diameter and vertical extent, that is centered on multi-phase, elongate, pencil-like tonalite intrusions, 200 m to 1,200 m in diameter and >2 km vertical extent. Large (>20 km 2 ) lithocaps associated with high-sulfidation epithermal systems and post-porphyry mineralization diatreme breccias characterize productive porphyry districts at Batu Hijau, Elang and Tumpangpitu. The known porphyry deposits with metal content exceeding 300 t Au and > 5 Mt Cu all formed less than 5 Ma, suggesting an important change in the metallogeny of the arc at this time. These giant porphyry deposits formed relatively rapidly, typically over a period of 30 to 860 k.y. during the Pliocene-Pleistocene between 5 and 2.5 Ma.Porphyry deposits along the eastern Sunda Arc display similar characteristic geological features to porphyry deposits elsewhere. Significant differences include low-K systems, dominance of hydrothermal biotite over K-feldspar, early intense actinolite alteration associated with ore, widespread shreddy chlorite after secondary biotite, narrow quartz-sericite-pyrite alteration zones, lack of development of C veins, large overlying lithocaps and abundant chalcocite-bornite-covellite veinlets associated with late overprinting epithermal systems. Hydrothermal oligoclase is also more abundant than K-feldspar in the central biotite-magnetite zones.

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“…The hypabyssal stocks in the Batu Hijau district are intruded into an early to middle Miocene volcano-sedimentary rock sequence (< 21 Ma based on biostratigraphy; Adams, 1984;Berggren et al, 1995) that reaches a thicknesses of up to 1500 m in south-western Sumbawa. The low-K 2 O, calcalkaline, sub-volcanic intrusive rocks in the Batu Hijau district have andesitic to quartz-dioritic and tonalitic compositions (Foden and Varne, 1980;Garwin, 2000) and were emplaced in several pulses during the late Miocene and Pliocene (Garwin, 2000). Over this multi-million-year magmatic history, a continuous geochemical evolution towards more fractionated lithologies is indicated by whole-rock chemistry and Fe-isotopic evidence of the magmatic rock suite in the Batu Hijau district (Garwin, 2000;Wawryk and Foden, 2017).…”

Section: Geological Backgroundmentioning

confidence: 99%

Resolving the timescales of magmatic and hydrothermal processes associated with porphyry deposit formation using zircon U–Pb petrochronology

et al. 2020

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Abstract. Understanding the formation of economically important porphyry Cu–Au deposits requires knowledge of the magmatic-to-hydrothermal processes that act within the much larger magmatic system and the timescales on which they occur. We apply high-precision zircon geochronology (chemical abrasion–isotope dilution–thermal ionisation mass spectrometry; CA–ID–TIMS) and spatially resolved zircon geochemistry (laser ablation inductively coupled plasma mass spectrometry; LA-ICP-MS) to constrain the magmatic evolution of the underlying magma reservoir at the Pliocene Batu Hijau porphyry Cu–Au deposit. We then use this extensive dataset to assess the accuracy and precision of different U–Pb dating methods of the same zircon crystals. Emplacement of the oldest pre- to syn-ore tonalite (3.736±0.023 Ma) and the youngest tonalite porphyry to cross-cut economic Cu–Au mineralisation (3.646±0.022 Ma) is determined by the youngest zircon grain from each sample, which constrains the duration of metal precipitation to fewer than 90±32 kyr. Overlapping spectra of single zircon crystallisation ages and their trace element distributions from the pre-, syn and post-ore tonalite porphyries reveal protracted zircon crystallisation together with apatite and plagioclase within the same magma reservoir over >300 kyr. The presented petrochronological data constrain a protracted early >200 kyr interval of melt differentiation and cooling within a large heterogeneous magma reservoir, followed by magma storage in a highly crystalline state and chemical and thermal stability over several tens of thousands of years during which fluid expulsion formed the ore deposit. Irregular trace element systematics suggest magma recharge or underplating during this final short time interval. The comparison of high-precision CA–ID–TIMS results with in situ LA-ICP-MS and a sensitive high-resolution ion microprobe (SHRIMP) U–Pb geochronology data from the same zircon grains allows a comparison of the applicability of each technique as a tool to constrain dates and rates on different geological timescales. All techniques provide accurate dates but with different precision. Highly precise dates derived by the calculation of the weighted mean and standard error of the mean of the zircon dates obtained by in situ techniques can lead to ages of unclear geological significance that are older than the maximum ages of emplacement given by the CA–ID–TIMS ages of the youngest zircons in each sample. This lack of accuracy of the weighted means is due to the protracted nature of zircon crystallisation in upper crustal magma reservoirs, suggesting that standard errors should not be used as a means to describe the uncertainty in those circumstances. We conclude from this and similar published studies that the succession of magma and fluid pulses forming a single porphyry deposit and similarly rapid geological events are too fast to be reliably resolved by in situ U–Pb geochronology and that assessing the tempo of ore formation requires CA–ID–TIMS geochronology.

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Evidence of a mantle contribution in the genesis of magmatic rocks from the Neogene Batu Hijau district in the Sunda Arc, South Western Sumbawa, Indonesia

Cited by 26 publications

References 67 publications

Resolving the timescales of magmatic and hydrothermal processes associated with porphyry deposit formation using zircon U-Pb petrochronology

Resolving the timescales of magmatic and hydrothermal processes associated with porphyry deposit formation using zircon U-Pb petrochronology

Tectonics and Geology of Porphyry Cu-Au Deposits along the Eastern Sunda Magmatic Arc, Indonesia

Resolving the timescales of magmatic and hydrothermal processes associated with porphyry deposit formation using zircon U–Pb petrochronology

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