scholarly journals Mineralogy, Geochemistry, and Age Constraints on the Axinite-Bearing Gukjeon Pb–Zn Skarn Deposit in the Miryang Area, South Korea

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 619
Author(s):  
Namhoon Kim ◽  
Sang-Mo Koh ◽  
Byoung-Woon You ◽  
Bum-Han Lee
Keyword(s):  
Age Dating ◽  
Southeastern Part ◽  
Zircon Age ◽  
Fine Grained ◽  
Magmatic Rocks ◽  
Temporal Relationships ◽  
The Pacific ◽  
Back Arc ◽  
Age Constraints ◽  
Shrimp Zircon

The axinite-bearing Gukjeon Pb–Zn deposit is hosted by the limestone, a member of the Jeonggaksan Formation, which, in turn, forms the part of the Jusasan subgroup of the Yucheon Group in the Gyeongsang Basin in the southeastern part of the Korean Peninsula. In this study, we attempted to interpret the spatial and temporal relationships among geologic events, including the mineralization of this deposit. We constructed a new 3D orebody model and suggested a relationship between skarn alteration and related mineralization. Mineralization timing was constrained using SHRIMP zircon age dating results combined with boron geochemistry on coeval intrusive rocks. Skarn alterations are restrictively found in several horizons of the limestone formation. The major skarn minerals are garnet (grossular), pyroxene (hedenbergite), amphibole (actinolite and ferro-actinolite), axinite (tizenite and ferro-axinite), and epidote (clinozoisite and epidote). The three stages of pre-skarn, syn-skarn, and post-skarn alteration are recognized within the deposit. The syn-skarn alteration is characterized by prograde metasomatic pyroxene and garnet, and the retrograde metasomatic amphibole, axinite, and epidote. Major skarn sulfide minerals are sphalerite, chalcopyrite, galena, and pyrite, which were predominantly precipitated during the retrograde stage and formed amphibole and axinite skarns. The skarn orebodies seem to be disc- or flat-shaped with a convex form at the central part of the orebodies. The vertical ascending and horizontal infiltration of boron-rich hydrothermal fluid probably controlled the geometry of the orebodies. Considering the whole-rock major, trace, and boron geochemical and geochronological results, the timing of Pb–Zn mineralization can be tightly constrained between the emplacement of boron-poor intrusion (fine-grained granodiorite, 82.8 Ma) and boron-rich intrusion (porphyritic andesite in Beomdori andesitic rocks, 83.8 Ma) in a back-arc basin setting. The boron for mineralization was sourced from late Cretaceous (Campanian), subduction-related magmatic rocks along the margin of the Pacific plate.

The Grenvillian assembly of Rodinia: Timing of accretion on the western margin of the Kalahari (Kaapvaal) Craton

2020 ◽  
Vol 123 (4) ◽  
pp. 441-464
Author(s):  
H.S. Van Niekerk ◽  
R. Armstrong ◽  
P. Vasconcelos
Keyword(s):  
Detrital Zircons ◽  
Age Dating ◽  
Granitic Gneiss ◽  
Detailed Model ◽  
Zircon Age ◽  
Western Margin ◽  
Tectonic History ◽  
Kalahari Craton ◽  
History Of ◽  
Shrimp Zircon

Abstract During the Grenvillian assembly of Rodinia, the Namaqua-Natal Metamorphic Province (NNMP) was formed as a result of the convergence of the Laurentia and Kalahari cratons. A detailed model for this accretion along the south-eastern margin of the Kalahari Craton has been established, but the tectonic history of the NNMP along the western margin of the Kalahari Craton has remained highly controversial. U-Pb SHRIMP zircon age dating of gneiss in the Kakamas Domain of the NNMP, as well as U-Pb SHRIMP age dating of detrital zircons and 40Ar/39Ar dating of metamorphic muscovite from sediments overlying the gneiss, confirms the presence of at least two separate events during the Namaqua-Natal Orogeny at ~1 166 Ma and 1 116 Ma. These events occurred after the Areachap Terrane was accreted onto the western margin of the Proto-Kalahari Craton during the Kheis Orogeny. 40Ar/39Ar ages derived from metamorphic muscovite formed in the metasediments of the Kheis terrane does not provide evidence for the timing of the Kheis Orogeny but suggests that it most likely only occurred after ~1 300 Ma and not at 1 800 Ma as commonly accepted. A U-Pb concordia age of ~1 166 Ma was derived from granitic gneiss in the Kakamas Domain of the Bushmanland Subprovince, possibly reflecting subduction and the initiation of continent-continent collision between the Proto-Kalahari Craton and the Bushmanland Subprovince. This granitic gneiss is nonconformably overlain by the metasediments of the Korannaland Group that contains metamorphic muscovite with 40Ar/39Ar ages of ~1 116 Ma. This age suggest that complete closure of the ocean between the Proto-Kalahari Craton and Bushmanland Subprovince probably occurred about 50 Ma after the intrusion of the ~1 166 Ma granitic gneisses.

Chronology of crustal growth and recycling in the Paleoproterozoic Amisk collage (Flin Flon Belt), Trans-Hudson Orogen, Canada

1999 ◽  
Vol 36 (11) ◽  
pp. 1807-1827 ◽  
Author(s):  
R A Stern ◽  
N Machado ◽  
E C Syme ◽  
S B Lucas ◽  
J David
Keyword(s):  
Upper Mantle ◽  
Tectonic Setting ◽  
Bulk Composition ◽  
Volcanic Rocks ◽  
Crust And Upper Mantle ◽  
Zircon Age ◽  
Magmatic Rocks ◽  
Main Period ◽  
Flin Flon ◽  
Back Arc

U-Pb zircon ages have been compiled for magmatic and sedimentary rocks from the low metamorphic grade portion of the Flin Flon greenstone belt, now recognized as a Paleoproterozoic tectonic collage. The "Amisk collage" formed in two major magmatic periods that were separated by an interval of intraoceanic accretionary tectonics. Pre-accretionary volcanic and plutonic rocks of arc and ocean-floor tectonic affinities have crystallization ages of 1.906-1.901 and 1.888-1.881 Ga; the earlier period was dominated by juvenile tholeiitic arc basalts and related back-arc-basin basalts, and the younger period by juvenile calc-alkaline volcanic rocks and turbidites. Intraoceanic accretion of the diverse tectono-stratigraphic assemblages may have commenced between 1.90 and 1.89 Ga, but the main period was 1.88-1.87 Ga. The post-accretionary period (1.876-1.838 Ga) was characterized by intrusion of juvenile calk-alkaline plutons generated by a successor arc that stitched the diverse pre-accretionary assemblages. Marine to subaerial volcaniclastic and epiclastic units were deposited in successor basins <=1.87 Ga (Schist-Wekusko suite), succeeded by alluvial-fluvial (Missi Group) to marine (Burntwood Group) sediments after 1.85 Ga. Despite the dominance of juvenile magmatic rocks within the collage, U-Pb zircon age and Nd-isotopic data show that older (>2.2-3.0 Ga) basement fragments were present throughout the development of the Amisk collage. An arc-back-arc system close to an Archean craton is proposed as the most likely tectonic setting during formation and accretion of the Amisk collage from 1.90 to 1.84 Ga. Subsequent continental collision during peak orogeny (1.84-1.81 Ga) is interpreted to have delaminated the lower crust and upper mantle of the collage, preferentially preserving crust of intermediate bulk composition.

A distant magmatic source for Cretaceous karst bauxites of Southern Apennines (Italy), revealed through SHRIMP zircon age dating

Terra Nova ◽  
2012 ◽  
Vol 24 (4) ◽  
pp. 326-332 ◽  
Author(s):  
Maria Boni ◽  
Steven M. Reddy ◽  
Nicola Mondillo ◽  
Giuseppina Balassone ◽  
Rich Taylor
Keyword(s):  
Age Dating ◽  
Southern Apennines ◽  
Zircon Age ◽  
Magmatic Source ◽  
Shrimp Zircon

Lower Silurian subduction-related volcanic rocks in the Chaleurs Group, northern New Brunswick, CanadaGeological Survey of Canada, Contribution No. 2008-0166.Contribution to Natural Resources Canada’s Targeted Geoscience Initiative 3 (2005–2010).

2008 ◽  
Vol 45 (9) ◽  
pp. 981-998 ◽  
Author(s):  
R. A. Wilson ◽  
C. R. van Staal ◽  
S. Kamo
Keyword(s):  
New Brunswick ◽  
Volcanic Rocks ◽  
Zircon Age ◽  
Mafic Rocks ◽  
Fine Grained ◽  
Lower Silurian ◽  
Narrow Width ◽  
Basaltic Flow ◽  
Back Arc

Early Silurian volcanic and subvolcanic rocks are preserved in the lower part of the Chaleurs Group at two locations in northern New Brunswick. At Quinn Point, mafic to intermediate rocks are hosted by sedimentary rocks of the Weir Formation, and at Pointe Rochette, a bed of felsic tuff occurs near the base of the Weir. These rocks are interpreted as the first evidence in New Brunswick of magmatism associated with Late Ordovician – Early Silurian subduction of Tetagouche–Exploits back-arc oceanic crust. At Quinn Point, mafic rocks include a thick basaltic flow or sill and intermediate to mafic cobbles in overlying conglomerate beds. The in situ mafic rocks and the conglomerate clasts are chemically alike and display subduction-related affinities on tectonic discrimination diagrams. At Pointe Rochette, fine-grained felsic tuff contains elevated Th and U and depleted high-field-strength elements, consistent with a subduction-influenced setting, although rare-earth element (REE) abundances are low and the REE profile is relatively flat. A U–Pb (zircon) age of 429.2 ± 0.5 Ma was obtained from the tuff, consistent with the late Llandovery to early Wenlock age of the overlying La Vieille Formation and coinciding with the latter stages of development of the Brunswick subduction complex. Volcanic rocks were emplaced in the arc to arc-trench gap region, probably reflecting local step-back of the magmatic axis due to accretion of continental back-arc ribbons. The low volume of Early Silurian subduction-influenced rocks is probably related to the relatively narrow width of the back-arc basin and the young, “warm” character of back-arc crust.

scholarly journals Cordilleran magmatism in Yukon and northern British Columbia: characteristics, temporal variations, and significance for the tectonic evolution of the northern Cordillera

2021 ◽  
Author(s):  
A Zagorevski ◽  
C R van Staal
Keyword(s):  
Building Blocks ◽  
Temporal Variations ◽  
Late Mesozoic ◽  
Magmatic Rocks ◽  
Temporal Relationships ◽  
Continental Arc ◽  
Lithospheric Extension ◽  
Tectonic Framework ◽  
Back Arc

Geochemical and temporal characterization of magmatic rocks is an effective way to test terrane definitions and to evaluate tectonic models. In the northern Cordillera, magmatic episodes are mostly interpreted as products of continental arc and back-arc settings. Re-evaluation of Paleozoic and Late Mesozoic magmatic episodes presented herein highlights fundamental gaps in the understanding of the tectonic framework of the northern Cordillera. In many cases, the character of magmatism and temporal relationships between various magma types do not support existing tectonic models. The present re-evaluation indicates that some of the magmatic episodes are best explained by lithospheric extension rather than arc magmatism. In addition, comparison to modern analogues suggests that many presently defined terranes are not the fundamental tectonic building blocks, but rather combine distinctly different tectonic elements that may not be related each other. Grouping of these distinctly different tectonic elements into single terranes hinders the understanding of Cordilleran evolution and its mineral deposits.

scholarly journals A subduction influence on ocean ridge basalts outside the Pacific subduction shield

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
A. Y. Yang ◽  
C. H. Langmuir ◽  
Y. Cai ◽  
P. Michael ◽  
S. L. Goldstein ◽  
...  
Keyword(s):  
Upper Mantle ◽  
The Arctic ◽  
Mantle Flow ◽  
Mantle Heterogeneity ◽  
Gakkel Ridge ◽  
The Pacific ◽  
Mid Ocean Ridge ◽  
The Pacific Ocean ◽  
Back Arc ◽  
Ocean Ridge

AbstractThe plate tectonic cycle produces chemically distinct mid-ocean ridge basalts and arc volcanics, with the latter enriched in elements such as Ba, Rb, Th, Sr and Pb and depleted in Nb owing to the water-rich flux from the subducted slab. Basalts from back-arc basins, with intermediate compositions, show that such a slab flux can be transported behind the volcanic front of the arc and incorporated into mantle flow. Hence it is puzzling why melts of subduction-modified mantle have rarely been recognized in mid-ocean ridge basalts. Here we report the first mid-ocean ridge basalt samples with distinct arc signatures, akin to back-arc basin basalts, from the Arctic Gakkel Ridge. A new high precision dataset for 576 Gakkel samples suggests a pervasive subduction influence in this region. This influence can also be identified in Atlantic and Indian mid-ocean ridge basalts but is nearly absent in Pacific mid-ocean ridge basalts. Such a hemispheric-scale upper mantle heterogeneity reflects subduction modification of the asthenospheric mantle which is incorporated into mantle flow, and whose geographical distribution is controlled dominantly by a “subduction shield” that has surrounded the Pacific Ocean for 180 Myr. Simple modeling suggests that a slab flux equivalent to ~13% of the output at arcs is incorporated into the convecting upper mantle.

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