scholarly journals Two-Stage Late Jurassic to Early Cretaceous Hydrothermal Activity in the Sakar Unit of Southeastern Bulgaria

Minerals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 266
Author(s):  
Krzysztof Szopa ◽  
Anna Sałacińska ◽  
Ashley P. Gumsley ◽  
David Chew ◽  
Petko Petrov ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Late Jurassic ◽  
Hydrothermal Activity ◽  
Two Stage ◽  
Accessory Minerals ◽  
Icp Ms ◽  
Two Stages ◽  
Age Constraints ◽  
Hydrothermal Veins

Southeastern Bulgaria is composed of a variety of rocks from pre-Variscan (ca. 0.3 Ga) to pre-Alpine sensu lato (ca. 0.15 Ga) time. The Sakar Unit in this region comprises a series of granitoids and gneisses formed or metamorphosed during these events. It is cut by a series of post-Variscan hydrothermal veins, yet lacks pervasive Alpine deformation. It thus represents a key unit for detecting potential tectonism associated with the enigmatic Cimmerian Orogenic episode, but limited geochronology has been undertaken on this unit. Here we report age constraints on hydrothermal activity in the Sakar Pluton. The investigated veins contain mainly albite–actinolite–chlorite–apatite–titanite–quartz–tourmaline–epidote and accessory minerals. The most common accessory minerals are rutile and molybdenite. Apatite and titanite from the same vein were dated by U–Pb LA–ICP-MS geochronology. These dates are interpreted as crystallization ages and are 149 ± 7 Ma on apatite and 114 ± 1 Ma on titanite, respectively. These crystallization ages are the first to document two stages of hydrothermal activity during the late Jurassic to early Cretaceous, using U–Pb geochronology, and its association with the Cimmerian orogenesis. The Cimmerian tectono-thermal episode is well-documented further to the east in the Eastern Strandja Massif granitoids. However, these are the first documented ages from the western parts of the Strandja Massif, in the Sakar Unit. These ages also temporally overlap with previously published Ar–Ar and K–Ar cooling ages, and firmly establish that the Cimmerian orogeny in the studied area included both tectonic and hydrothermal activity. Such hydrothermal activity likely accounted for the intense albitization found in the Sakar Unit.

scholarly journals New U-Pb geochronological data on the age of volcanic-plutonic assemblage of Oloy belt, Alazey-Oloy fold system (West Chukotka)

2019 ◽  
Vol 487 (6) ◽  
pp. 653-658
Author(s):  
T. V. Kara ◽  
M. V. Luchitskaya ◽  
S. M. Katkov ◽  
E. A. Belousova
Keyword(s):  
Early Cretaceous ◽  
Late Jurassic ◽  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Geochronological Data ◽  
Fold System ◽  
Hypabyssal Intrusions ◽  
Icp Ms ◽  
Age Limits ◽  
Felsic Volcanic

New U-Pb (SIMS and LA-ICP-MS) geochronological data for rocks of Egdygkych complex of hypabyssal intrusions, Nichan and Vukney plutons, and felsic volcanic rocks and tuffs from host strata of Oloy volcanic belt of Alasey-Oloy fold system are obtained. Concordant ages of Egdygkych complex rocks correspond to Early Cretaceous (Berriasian-Valanginian), those for host strata, to the end of Late Jurassic (Tithonian) - beginning of Early Cretaceous (Berriasian). New U-Pb geochronological data allow confidently to distinguish uniform volcanic-plutonic assemblage of Late Jurassic (Tithonian) - Early Cretaceous (Berriasian-Valanginian) age of Oloy volcanic belt. Obtained data more definitely determine age limits of Au-Mo-Cu mineralization, associated with contacts between rocks of Egdydkych complex and host volcanic-sedimentary rocks or contacts of separated intrusive phases.

Late Jurassic to Early Cretaceous magmatism in the Xiong’ershan gold district, central China: implications for gold mineralization and geodynamics

2019 ◽  
Vol 157 (3) ◽  
pp. 435-457
Author(s):  
Zhenshan Pang ◽  
Fuping Gao ◽  
Yangsong Du ◽  
Yilun Du ◽  
Zhaojian Zong ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Inductively Coupled Plasma ◽  
Late Jurassic ◽  
Gold Mineralization ◽  
Central China ◽  
Inductively Coupled ◽  
Icp Ms ◽  
Metamorphic Basement ◽  
Plasma Mass Spectrometry ◽  
Cretaceous Magmatism

AbstractThe Xiong’ershan area is the third largest gold-producing district in China. The Late Jurassic to Early Cretaceous magmatism in the Xiong’ershan area can be divided into two episodes: early (165–150 Ma) and late (138–113 Ma). Laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS) zircon U–Pb dating yields ages of 160.7 ± 0.6 Ma and 127.2 ± 1.0 Ma for the Wuzhangshan and Huashan monzogranites in the Xiong’ershan area, respectively, representing the two magmatic episodes. The Wuzhangshan monzogranites exhibit adakite-like geochemical features (e.g. high Sr/Y ratios, low Yb and Y contents). Their Sr–Nd–Hf isotopic compositions are consistent with those of the amphibolites of the Taihua Group, indicating that the Wuzhangshan monzogranites were formed from partial melting of the Taihua Group metamorphic rocks. Compared to the Wuzhangshan rocks, the Huashan monzogranites have higher MgO, Cr, Co and Ni contents, but lower Sr/Y and Fe3+/Fe2+. All the samples from the Huashan monzogranites plot in the area between the Taihua Group amphibolite rocks and the mantle rocks in the (87Sr/86Sr)t vs εNd(t) and age vs εHf(t) diagrams, suggesting that the Huashan monzogranites were probably generated by mixing of mantle-derived magmas and the Taihua Group metamorphic basement melts. The gold mineralization (136–110 Ma) is coeval with the emplacement of the late-episode magmas, implying that crustal–mantle mixed magma might be a better target for gold mineralization compared to the ancient metamorphic basement melt. The data presented in this study further indicate that the transformation of the lithosphere from thickening to thinning in the Xiong’ershan area probably occurred between ~160 Ma and ~127 Ma, and that the gold mineralization in this area was probably related to lithospheric thinning.

Discrete Jurassic and Cretaceous Mineralization Events at the Xiangdong W(-Sn) Deposit, Nanling Range, South China

2020 ◽  
Vol 115 (2) ◽  
pp. 385-413 ◽  
Author(s):  
Yi-Qu Xiong ◽  
Yong-Jun Shao ◽  
Yanbo Cheng ◽  
Shao-Yong Jiang
Keyword(s):  
Early Cretaceous ◽  
South China ◽  
Late Jurassic ◽  
Stage I ◽  
Stage Ii ◽  
Quartz Veins ◽  
Nanling Range ◽  
Metallogenic Belt ◽  
Two Stages ◽  
Highly Evolved

Abstract The Xiangdong W(-Sn) deposit is hosted in the Dengfuxian multiphase granites (biotite, two-mica, and muscovite granites) within the Nanling Range metallogenic belt in south China. Previous studies suggested that the W(-Sn) mineralization in the Xiangdong deposit is related to the Late Jurassic two-mica granite, whereas recently W-Sn–bearing quartz veins have also been identified in muscovite granite. We present new cassiterite and zircon U-Pb ages to constrain the timing of W-Sn mineralization and related granitic magmatism. Our laser ablation-inductively coupled plasma-mass spectrometry U-Pb dating of zircon grains, combined with previous zircon ages, in addition to the trace element composition of the muscovite granite, suggest the muscovite granite in the Dengfuxian pluton was emplaced at 145 to 142 Ma and shows highly evolved features. Cassiterite grains from the ore-bearing veins in two-mica granite yielded U-Pb ages of 151.6 ± 3.7 and 141 to 138 Ma, whereas cassiterite grains from quartz veins occurring in muscovite granite yielded a U-Pb age of 136.8 ± 3.3 Ma. The new ages and detailed geologic evidence indicate that the Early Cretaceous muscovite granite is also genetically related to W-Sn mineralization. Combining this with previously published data from the Late Jurassic two-mica granites and related mineralization, we suggest that there were two stages of W-Sn mineralization at Xiangdong. Arsenopyrite geothermometry from the two stages suggests temperatures of 300° to 491° and 308° to 450°C in stage I and stage II, respectively. Wolframite grains from the two stages also show different characteristics and patterns for their major and trace elements. The enrichment in Sc in wolframite suggests low-pH and low-Eh conditions for a fluid containing F– and/or PO43− complexes during stage I, whereas higher contents of Nb and Ta and lower contents of Sc in wolframite from stage II indicate relatively lower pH and higher Eh conditions. In combination with data from other recent studies, we propose that the 145 to 130 Ma interval represents a newly recognized W-Sn metallogenic period linked with highly evolved granites in the Nanling Range metallogenic belt. The Early Cretaceous muscovite granite is an important new target for W and Sn resources in south China.

scholarly journals Rock-Forming (Biotite and Plagioclase) and Accessory (Zircon) Minerals Geochemistry as an Indicator of the Metal Fertility of Magmas by the Example of Au-Cu-Fe-Skarn Deposits in Eastern Transbaikalia

Minerals ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 50
Author(s):  
Yury O. Redin ◽  
Anna A. Redina ◽  
Viktor P. Mokrushnikov ◽  
Alexandra V. Malyutina ◽  
Vladislav F. Dultsev
Keyword(s):  
Early Cretaceous ◽  
Late Jurassic ◽  
Accessory Zircon ◽  
Accessory Minerals ◽  
Magmatic Rocks ◽  
The World ◽  
Eastern Transbaikalia ◽  
Skarn Deposits ◽  
Cretaceous Magmatism ◽  
Gold Bearing

Many gold and gold-bearing complex deposits related to the Late Jurassic and Early Cretaceous magmatism are known in Eastern Transbaikalia. The largest deposits are the Lugokan, the Kultuma and the Bystrinsky. These deposits are in a paragenetic relationship with the Late Jurassic magmatic rocks of the Shakhtama complex. According to the available data, the total resources of gold in these three deposits are estimated to be approximately 443 tons: the Lugokan, Au~53 tons, Cu~302 thousand tons; the Kultuma, Au~121 tons, Cu~587 thousand tons, Fe~33 mln t; the Bystrinsky, Au~269 tons, Cu~2070 thousand tons, Fe~67 mln t. One of the main aims of this work was to reveal the criteria of fertility for the classical porphyry type, based on the specific geochemical features of rock-forming and accessory minerals. A comparison of the obtained results with other data on the large porphyry and skarn deposits of the world showed that the magmatic rocks of the Bystrinsky massif, specifically porphyry species dated 159.6–158.6 Ma, are potentially ore-bearing for the porphyry type mineralization. The magmatic rocks that widely occur at the Lugokan and Kultuma deposits are most close to the Fe-skarn deposits. The best indicators of the magma fertility for the porphyry rocks are Ce/Ce*, Eu/Eu*, Yb/Dy, (Ce/Nd)/Y in zircons. Thus, magmatic rocks characterized by Ce/Ce* > 100, Eu/Eu* > 0.4, Yb/Dy > 5.0 and (Ce/Nd)/Y > 0.01 may be classified as high fertile for the classical porphyry mineralization in Eastern Transbaikalia. The plagioclase and biotite chemistry data also showed that the magmatic rocks that occurred at the Bystrinsky deposit are the most fertile for the porphyry type mineralization. The magmatic rocks classified as ore-bearing porphyry type have Al* > 1 in plagioclase, high values of IV(F) and IV(F/Cl) and low ratios of X(F)/X(OH) in biotites. The assessment of the metal fertility of magmatic rocks is most effective in combination with data on both the composition of rock-forming and accessory minerals. The obtained data may be used to develop the methods of prediction and search for gold, copper and iron mineralization.

LA-ICP-MS U–Pb zircon, columbite-tantalite and40Ar–39Ar muscovite age constraints for the rare-element pegmatite dykes in the Altai orogenic belt, NW China

2016 ◽  
Vol 155 (3) ◽  
pp. 707-728 ◽  
Author(s):  
QIFENG ZHOU ◽  
KEZHANG QIN ◽  
DONGMEI TANG ◽  
CHUNLONG WANG ◽  
PATRICK ASAMOAH SAKYI
Keyword(s):  
Late Jurassic ◽  
Middle Triassic ◽  
Temporal Distribution ◽  
Middle Permian ◽  
Magmatic Activity ◽  
Weighted Mean ◽  
Rare Element ◽  
Nw China ◽  
Icp Ms ◽  
Age Constraints

AbstractThe Chinese Altai is renowned for its rich rare-element resources. Nine representative rare-element (REL) pegmatites were dated using LA-ICP-MS and40Ar–39Ar methods. The columbite grains yield a weighted mean206Pb/238U age of 239.6±3.8 Ma for the Dakalasu (Be-Nb-Ta) pegmatite and concordia U–Pb ages of 258.1±3.1 Ma and 262.3±2.5 Ma for the Xiaokalasu (Li-Nb-Ta) pegmatite. The zircons display a weighted mean206Pb/238U age of 198.5±2.5 Ma for the Husite (Be) pegmatite and concordia U–Pb ages of 194.3±1.6 Ma and 248.2±2.2 Ma for the Qunkuer (Be) and Taerlang (barren) pegmatites. The muscovite40Ar–39Ar dating gives plateau ages of 286.4±1.6 Ma, 297.0±2.6 Ma, 265.2±1.5 Ma, 178.8±1.0 Ma, 162.2±0.9 Ma, 237.7±1.3 Ma, 237.4±1.2 Ma and 231.9±1.2 Ma for the Talate (Li-Be-Nb-Ta), Baicheng (Nb-Ta), Kangmunagong (barren), Husite (Be), Qunkuer (Be-Nb-Ta), Xiaokalasu (Li-Nb-Ta), Weizigou (Be) and Taerlang (barren) pegmatites, respectively. These new ages coupled with previous geochronological work suggest that the REL pegmatites in the Chinese Altai formed during early Permain – Late Jurassic time. The REL pegmatites located in the Central Altaishan terrane are younger than those in the Qiongkuer–Abagong terrane, showing a correlation with the coeval and adjacent granites. The formation of the REL pegmatites and these granites indicates frequent and strong magmatic activity in the post-orogenic and anorogenic setting. The spatial and temporal distribution of pegmatites and granites reveals a magmatism path from the SE (of age early–middle Permian), to the NW (middle Permian – Middle Triassic) and finally to the central part (Middle Triassic – Jurassic) of the Chinese Altai.

scholarly journals Late jurassic-early cretaceous volcanic-plutonic assemblage of Oloy Belt, Western Chukotka: U-Pb SIMS and LA-ICP-MS data

2019 ◽  
Vol 64 (3) ◽  
pp. 421-433
Author(s):  
Taras V. Kara ◽  
◽  
Marina V. Luchitskaya ◽  
Sergey M. Katkov ◽  
Elena A. Belousova ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Late Jurassic ◽  
Icp Ms

AGE MODEL FOR LATE JURASSIC THROUGH EARLY CRETACEOUS USED IN THE GEOLOGIC TIMESCALE 2012/2016 REFERENCE SCALES

2018 ◽  
Author(s):  
James G. Ogg ◽  
◽  
Chunju Huang ◽  
Chunju Huang ◽  
Linda A. Hinnov ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Late Jurassic ◽  
Age Model

New constraints from zircon, monazite and uraninite dating on the commencement of sedimentation in the Cuddapah basin, India

2017 ◽  
Vol 155 (6) ◽  
pp. 1230-1246 ◽  
Author(s):  
DEBIDARSANI SAHOO ◽  
KAMAL LOCHAN PRUSETH ◽  
DEWASHISH UPADHYAY ◽  
SAMEER RANJAN ◽  
DIPAK C. PAL ◽  
...  
Keyword(s):  
Wide Spectrum ◽  
Hydrothermal Activity ◽  
Time Span ◽  
Detrital Zircons ◽  
Cuddapah Basin ◽  
Relative Timing ◽  
Considerable Time ◽  
Long Span ◽  
Considerable Confusion ◽  
Age Constraints

AbstractThe Cuddapah basin in southern India, consisting of the Palnad, Srisailam, Kurnool and Papaghni sub-basins, contains unmetamorphosed and undeformed sediments deposited during a long span of time in the Proterozoic. In the absence of robust age constraints, there is considerable confusion regarding the relative timing of sedimentation in these sub-basins. In this study, U–Pb isotopic dating of zircon and U–Th–Pbtotaldating of monazite and uraninite from the gritty quartzite that supposedly belongs to the formation Banganapalle Quartzite have been used to constrain the beginning of sedimentation in the Palnad sub-basin. Magmatic and detrital zircons recording an age of 2.53 Ga indicate that the sediments were derived from the granitic basement or similar sources and were deposited after 2.53 Ga. Hydrothermally altered zircons both in the basement and the cover provide concordant ages of 2.32 and 2.12 Ga and date two major hydrothermal events. Thus, the gritty quartzite must have been deposited sometime between 2.53 and 2.12 Ga and represents the earliest sediments in the Cuddapah basin. Monazite and uraninite give a wide spectrum of ages between 2.5 Ga and 150 Ma, which indicates several pulses of hydrothermal activity over a considerable time span, both in the basement granite and the overlying quartzite. The new age constraints suggest that the gritty quartzite may be stratigraphically equivalent to the Gulcheru Quartzite that is the oldest unit in the Cuddapah basin, and that a sedimentary/erosional hiatus exists above it.

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