Paul Eizenhöfer | University of Pittsburgh (original) (raw)
Papers by Paul Eizenhöfer
Ages and Hf isotopes of detrital zircons from the Permian strata in the Bengbatu area (Inner Mongolia) and tectonic implications
Geoscience Frontiers
Zircon U-Pb geochronology and Hf isotopes of major lithologies from the Jiaodong Terrane: Implications for the crustal evolution of the Eastern Block of the North China Craton
ABSTRACT The Jiaodong Terrane of the Eastern Shandong Complex in the Eastern Block of the North C... more ABSTRACT The Jiaodong Terrane of the Eastern Shandong Complex in the Eastern Block of the North China Craton (NCC) consists predominantly of Archean granitoid gneisses with minor supracrustal rock enclaves or lenses. This study presents new zircon LA-ICP-MS U-Pb and Lu-Hf isotopic data for these lithologies, which help to better understand the Archean crustal evolution of the Eastern Block of the NCC. Magmatic zircon U-Pb data reveal that zircons in the supracrustal rocks and granitoid gneisses were generated by multi-stage events at ~ 2.9 Ga, ~ 2.7 Ga and ~ 2.5 Ga. Metamorphic zircon U-Pb data obtained for these rocks show distinct metamorphic ages at ~ 2.50 and ~ 1.9-1.8 Ga, suggesting that the Jiaodong Terrane experienced a regional metamorphic event at the end of the Neoarchean and encountered reworking by a tectonothermal event that was associated with the formation of the Paleoproterozoic Jiao-Liao-Ji Belt. Magmatic zircons have variable εHf(t) values from − 5.5 to + 7.7 with model ages of 3.92-2.57 Ga, of which most εHf(t) values are positive with a predominant peak of model ages at 3.4-3.1 Ga and a subordinate peak at 2.8-2.7 Ga. These Hf features reveal major juvenile crustal growth stages with significant additions of older crustal materials at 3.4-3.1 Ga and 2.8-2.7 Ga, and a crustal reworking event with minor juvenile additions at ~ 2.5 Ga in the Jiaodong Terrane.
Zircon U–Pb geochronology and Hf isotopes of major lithologies from the Jiaodong Terrane: Implications for the crustal evolution of the Eastern Block of the North China Craton
Geochronological and Hf isotopic variability of detrital zircons in Paleozoic strata across the accretionary collision zone between the North China craton and Mongolian arcs and tectonic implications
The Central Asian orogenic belt formed by accretion subsequent to the contraction of the paleo–As... more The Central Asian orogenic belt formed by accretion subsequent to the contraction of the paleo–Asian Ocean, and its southeastern segment terminated along the Solonker suture zone, amalgamating the Mongolian arcs and the North China craton by the end of the Early Triassic. Since typical regional collisional features are absent, its tectonic evolution remains speculative. An investigation into the variability of detrital zircon U-Pb ages and Hf ratios in Permian strata along a southeast-northwest transect from the Mongolian arcs to the North China craton reveals distinct differences: Northern basins carry a broad Mesoproterozoic to latest Precambrian age signature, and their sedimentary source terranes are of mixed juvenile to crustal magmatic origin. In contrast, southern basins contain detritus from the North China craton, and their sources are of dominantly crustal contaminated magmatic origin. Provenance analysis suggests that in the early Paleozoic (ca. 429 Ma), the paleo–Asian Ocean was consumed along the Uliastai arc and the North China craton, initiating the formation of the northern and southern accretionary orogens, respectively. By the end of the middle Carboniferous, the Mongolian arcs were consolidated after the accretion of the Uliastai arc. In the late Carboniferous (ca. 314 Ma), the Hegenshan back-arc basin opened, detaching the Northern accretionary orogen. While subduction continued there, it may have temporarily ceased in the south after the accretion of a microcontinent (ca. 300 Ma). By the end of the Middle Permian (ca. 269 Ma), back-arc basin closure led to the formation and obduction of the suprasubduction zone Hegenshan ophiolite. Eventually, the paleo–Asian Ocean closed by double-sided subduction. Such accretionary wedge-wedge collision would not involve continental deep subduction, unlike other continental collisions. The early stages of the sequence likely resembled a Pacific-type scenario dominated by the subduction of oceanic lithosphere, including a Japanese Sea–type back-arc basin opening. The late stages involved the accretion of large-scale continental blocks, ultimately leading to final ocean closure, which may be similar to the archipelago-type setting of present-day Southeast Asia.
The Solonker Suture Zone is commonly recognised as the location of the Late Permian to Early Tria... more The Solonker Suture Zone is commonly recognised as the location of the Late Permian to Early Triassic closure of the Palaeo-Asian Ocean in the southeastern segment of the Central Asian Orogenic Belt. However, the absence of typical suture-related features, as a consequence of uncommon collisional geometries, gave it a cryptic nature. Thus, the tectonic setting, which led to suturing, still remains enigmatic. A geochemical characterisation of Permian sedimentary and volcanic rocks across the suture was carried out. Supplemented with Hf and Nd isotopic analyses, this approach enables not only a better definition of such regional suture, but also estimates on the long-controversial issue of net crustal growth in accretionary tectonic environments.
The results indicate short sedimentary transport distances between the arc basins and their provenances, of which the studied volcanic rocks were a major contributor. Similar enrichment and depletion patterns with respect to N-MORB and average continental crust further corroborate a close source-sediment relationship. Immobile element provenance analyses indicate that the active continental northern margin of the North China Craton was a major source for arc basins to the south of the Solonker Suture Zone. To its north, arc basins are interpreted to be sourced by a more complex mixture of provenances, e.g., the Baolidao volcanic arc suite and the heterogenous Precambrian basement of southern Mongolia. An overall collisional tectonic setting across the suture is recognised. The geochemical signature of sedimentary rocks to the south of the suture points at an active continental arc setting, whereas the bimodal geochemical distribution of the samples to the north show a contemporaneous active oceanic island arc as well as passive margin environment. These features favour a double-sided subduction of the Palaeo-Asian Ocean beneath the North China Craton and the Mongolian Arcs throughout the Palaeozoic, including back-arc basin opening north of the suture in the Permian.
Analysis of Hf and Nd isotopic compositions revealed that magmas to the south were produced involving significant crustal contamination, thus having less radiogenic compositions. North of the suture, however, isotopic compositions tend to be more radiogenic, implying a more juvenile contribution. However, the bulk isotopic compositions are close to present-day CHUR, suggesting that crustal reworking appears to be equally balanced by juvenile addition during the Palaeozoic closure of the Palaeo-Asian Ocean across the Solonker Suture Zone.
There is a broad consensus that the Solonker Suture Zone marks the final closure of the Paleo-Asi... more There is a broad consensus that the Solonker Suture Zone marks the final closure of the Paleo-Asian Ocean, which led to the formation of the eastern segment of the Central Asian Orogenic Belt. However, when and how the final closure occurred still remains controversial. To address this issue, provenance analysis of Permian sedimentary rocks of arc basins along the Xar Moron River was carried out. Geochemical analysis revealed a close relationship between the sedimentary and volcanic rock suite in the study region suggesting short transport distances and a complex convergent arc setting. Detrital zircon U-Pb analysis identified two major age provenances: (1) the Precambrian basement of the North China Craton (~2497 Ma and ~1844 Ma) and (2) the Paleozoic Southern Accretionary Orogen along the northern margin of North China (~436 Ma and ~269 Ma). The present locations of identified age provenances indicate southward subduction beneath the northern margin of North China. A comparison of the youngest age population in the sedimentary rocks with U-Pb ages obtained for subduction-related volcanic rocks implies that the Solonker Suture Zone formed from the Late Permian to Early Triassic. The results of our study advocate a complex Permian arc system which was probably similar to present-day Southeast Asia.
A detrital zircon U-Pb and Lu-Hf isotopic study was carried out on the Middle Silurian to Late Ca... more A detrital zircon U-Pb and Lu-Hf isotopic study was carried out on the Middle Silurian to Late Carboniferous sedimentary strata of the northwestern Tarim Craton in order to understand accretionary processes in the southern part of the Central Asian Orogenic Belt. Detrital zircons from these strata yielded U-Pb ages clustering around 2.8-2.3 Ga, 2.0-1.7 Ga, 1.3-0.9 Ga, 880-660 Ma and 500-400 Ma, with age populations and Hf isotopic signatures matching those of magmatic rocks in the Tarim Craton and the Central Tianshan Block. Abundant 500-400 Ma detrital zircons most likely reflect deposition in a retro-arc foreland basin inboard of an Andean-type magmatic arc to the north, supporting the northern Tarim-Central Tianshan connection during Early Paleozoic time. The absence of 380-310 Ma zircon population in the Carboniferous siliciclastic rocks suggests that the Central Tianshan Block may have been separated from the Tarim Craton in the Early Devonian, caused by the inter-arc/back-arc opening of the South Tianshan Ocean. We propose an accretionary orogenic model switching from advancing to retreating mode during Paleozoic time in the southwestern part of the Paleo-Asian Ocean. This transition most likely occurred coevally with the rifting of Southeast Asian blocks from the northeastern margin of Gondwana.
The Jiaodong Terrane of the Eastern Shandong Complex in the Eastern Block of the North China Crat... more The Jiaodong Terrane of the Eastern Shandong Complex in the Eastern Block of the North China Craton (NCC) consists predominantly of Archean granitoid gneisses with minor supracrustal rock enclaves or lenses. This study presents new zircon LA-ICP-MS U–Pb and Lu–Hf isotopic data for these lithologies, which help to better understand the Archean crustal evolution of the Eastern Block of the NCC. Magmatic zircon U–Pb data reveal that zircons in the supracrustal rocks and granitoid gneisses were generated by multi-stage events at ~ 2.9 Ga, ~ 2.7 Ga and ~ 2.5 Ga. Metamorphic zircon U–Pb data obtained for these rocks show distinct metamorphic ages at ~ 2.50 and ~ 1.9–1.8 Ga, suggesting that the Jiaodong Terrane experienced a regional metamorphic event at the end of the Neoarchean and encountered reworking by a tectonothermal event that was associated with the formation of the Paleoproterozoic Jiao–Liao–Ji Belt. Magmatic zircons have variable εHf(t) values from − 5.5 to + 7.7 with model ages of 3.92–2.57 Ga, of which most εHf(t) values are positive with a predominant peak of model ages at 3.4–3.1 Ga and a subordinate peak at 2.8–2.7 Ga. These Hf features reveal major juvenile crustal growth stages with significant additions of older crustal materials at 3.4–3.1 Ga and 2.8–2.7 Ga, and a crustal reworking event with minor juvenile additions at ~ 2.5 Ga in the Jiaodong Terrane.
Apatite fission track dating of five samples from Cenozoic volcanic strata in the Nimu District i... more Apatite fission track dating of five samples from Cenozoic volcanic strata in the Nimu District in the southern Gangdese Terrane exhibits single population grain ages with a single mean age and associated central ages ranging from 6.8 ± 0.6 Ma to 9.7 ± 1.2 Ma. Mean track lengths are between 12.9 ± 1.7 µm and 14.2 ± 2.3 µm with a single peak characteristic of a single thermal event. The newly documented ages coincide well with the age of high sedimentation rates in the North Tibet Basin that resulted from a 9–5 Ma compressional event. Track length modeling allows three stages to be identified in the sample cooling. The first stage (12–8 Ma) records a period of relative stability with little, if any, cooling at temperatures of 120–110°C suggesting this region had low relief. The second stage (8–2 Ma) reflects rapid cooling with temperatures decreasing from ∼110°C to surface temperatures of ∼15°C. This stage can be related to far-field effects of the Himalayan collision, which probably generated the surface uplift and relief that defines the present-day Gangdese Mountains. The mean uplift rate of this period is estimated to be 1.41–0.95 mm/y with total uplift reaching ∼5900 m. The final stage is related to surface evolution since the Pliocene.
The geological attraction of the Heilongjiang Complex, extending along a suture zone between the ... more The geological attraction of the Heilongjiang Complex, extending along a suture zone between the Jiamusi and Songliao blocks in Northeast China, resides in excellent exposures of blueschists, which occur in association with granitic gneisses, marbles, meta-ultramafic rocks, greenschists, quartzites, muscovite–albite schists and two-mica schists from the complex. However, controversy has long surrounded the ages and tectonic settings of mafic protoliths of the blueschists from the complex. The lithological association and major and trace element compositions indicate that the ultramafic–mafic protoliths of the Yilan blueschists can be subdivided into the tholeiitic and alkali groups, both of which were derived from partial melting of garnet-facies peridotites, but at different degrees of melting. Magmatic zircons from a tholeiitic blueschist sample yield a 206Pb/238U age of 275 ± 2 Ma, interpreted as its protolithic age. The sample also contains large amounts of older inherited zircons up to 1200 Ma, which, together with the geochemical features of the sample, indicate that the tholeiitic basalts were generated in a continental rift. The further development of the rift led to the formation of an ocean between the Jiamusi and Songliao blocks, in which some ocean islands developed, represented by the alkali mafic protoliths of the Yilan blueschists, as supported by geochemical data. Magmatic zircons from an alkaline mafic blueschist sample yield a 206Pb/238U age of 141.8 ± 1 Ma, indicating that the ocean between the Jiamusi and Songliao blocks had not been closed by ~ 141 Ma, not at 210–180 Ma as previously considered.
Books by Paul Eizenhöfer
Geologie des Betancuria Massivs auf Fuerteventura, Kanarische Inseln: Eine geologische Geländeuntersuchung des plutonischen Basalkomplexes und ... nördlich von Pájara (German Edition)
Die Kanarischen Inseln gehören zusammen mit den Azoren, Madeira, Selvagens und Kapverden zu den m... more Die Kanarischen Inseln gehören zusammen mit den Azoren, Madeira, Selvagens und Kapverden zu den mittelatlantischen Vulkaninseln. Der vorwiegend vulkanische Aufbau der Kanaren erfolgte im Wesentlichen in drei Phasen: der sogenannten Prä-Schild-Phase, gefolgt von der Schild-Phase und abschließend der Post-Schild-Phase. Während auf den meisten Inseln jüngerer Magmatismus bis heute dominiert (rezent submarin nahe El Hierro), zeichent sich Fuerteventura zusätzlich durch die geologische Archivierung des ältesten aktiven Vulkanismus vor mehr als 65 Millionen Jahren aus. Dies formte den um die Ortschaft Pájara aufgeschlossenen Basalkomplex. Die hier vorgelegte Arbeit umfasst eine detaillierte geologische Geländeuntersuchung einschließlich geologischer Kartierung innerhalb dieses Basalkomplexes. Sie eignet sich als Basis für weitere geologische Untersuchungen, aber auch als geologischer Führer für den interessierten Laien.
Ages and Hf isotopes of detrital zircons from the Permian strata in the Bengbatu area (Inner Mongolia) and tectonic implications
Geoscience Frontiers
Zircon U-Pb geochronology and Hf isotopes of major lithologies from the Jiaodong Terrane: Implications for the crustal evolution of the Eastern Block of the North China Craton
ABSTRACT The Jiaodong Terrane of the Eastern Shandong Complex in the Eastern Block of the North C... more ABSTRACT The Jiaodong Terrane of the Eastern Shandong Complex in the Eastern Block of the North China Craton (NCC) consists predominantly of Archean granitoid gneisses with minor supracrustal rock enclaves or lenses. This study presents new zircon LA-ICP-MS U-Pb and Lu-Hf isotopic data for these lithologies, which help to better understand the Archean crustal evolution of the Eastern Block of the NCC. Magmatic zircon U-Pb data reveal that zircons in the supracrustal rocks and granitoid gneisses were generated by multi-stage events at ~ 2.9 Ga, ~ 2.7 Ga and ~ 2.5 Ga. Metamorphic zircon U-Pb data obtained for these rocks show distinct metamorphic ages at ~ 2.50 and ~ 1.9-1.8 Ga, suggesting that the Jiaodong Terrane experienced a regional metamorphic event at the end of the Neoarchean and encountered reworking by a tectonothermal event that was associated with the formation of the Paleoproterozoic Jiao-Liao-Ji Belt. Magmatic zircons have variable εHf(t) values from − 5.5 to + 7.7 with model ages of 3.92-2.57 Ga, of which most εHf(t) values are positive with a predominant peak of model ages at 3.4-3.1 Ga and a subordinate peak at 2.8-2.7 Ga. These Hf features reveal major juvenile crustal growth stages with significant additions of older crustal materials at 3.4-3.1 Ga and 2.8-2.7 Ga, and a crustal reworking event with minor juvenile additions at ~ 2.5 Ga in the Jiaodong Terrane.
Zircon U–Pb geochronology and Hf isotopes of major lithologies from the Jiaodong Terrane: Implications for the crustal evolution of the Eastern Block of the North China Craton
Geochronological and Hf isotopic variability of detrital zircons in Paleozoic strata across the accretionary collision zone between the North China craton and Mongolian arcs and tectonic implications
The Central Asian orogenic belt formed by accretion subsequent to the contraction of the paleo–As... more The Central Asian orogenic belt formed by accretion subsequent to the contraction of the paleo–Asian Ocean, and its southeastern segment terminated along the Solonker suture zone, amalgamating the Mongolian arcs and the North China craton by the end of the Early Triassic. Since typical regional collisional features are absent, its tectonic evolution remains speculative. An investigation into the variability of detrital zircon U-Pb ages and Hf ratios in Permian strata along a southeast-northwest transect from the Mongolian arcs to the North China craton reveals distinct differences: Northern basins carry a broad Mesoproterozoic to latest Precambrian age signature, and their sedimentary source terranes are of mixed juvenile to crustal magmatic origin. In contrast, southern basins contain detritus from the North China craton, and their sources are of dominantly crustal contaminated magmatic origin. Provenance analysis suggests that in the early Paleozoic (ca. 429 Ma), the paleo–Asian Ocean was consumed along the Uliastai arc and the North China craton, initiating the formation of the northern and southern accretionary orogens, respectively. By the end of the middle Carboniferous, the Mongolian arcs were consolidated after the accretion of the Uliastai arc. In the late Carboniferous (ca. 314 Ma), the Hegenshan back-arc basin opened, detaching the Northern accretionary orogen. While subduction continued there, it may have temporarily ceased in the south after the accretion of a microcontinent (ca. 300 Ma). By the end of the Middle Permian (ca. 269 Ma), back-arc basin closure led to the formation and obduction of the suprasubduction zone Hegenshan ophiolite. Eventually, the paleo–Asian Ocean closed by double-sided subduction. Such accretionary wedge-wedge collision would not involve continental deep subduction, unlike other continental collisions. The early stages of the sequence likely resembled a Pacific-type scenario dominated by the subduction of oceanic lithosphere, including a Japanese Sea–type back-arc basin opening. The late stages involved the accretion of large-scale continental blocks, ultimately leading to final ocean closure, which may be similar to the archipelago-type setting of present-day Southeast Asia.
The Solonker Suture Zone is commonly recognised as the location of the Late Permian to Early Tria... more The Solonker Suture Zone is commonly recognised as the location of the Late Permian to Early Triassic closure of the Palaeo-Asian Ocean in the southeastern segment of the Central Asian Orogenic Belt. However, the absence of typical suture-related features, as a consequence of uncommon collisional geometries, gave it a cryptic nature. Thus, the tectonic setting, which led to suturing, still remains enigmatic. A geochemical characterisation of Permian sedimentary and volcanic rocks across the suture was carried out. Supplemented with Hf and Nd isotopic analyses, this approach enables not only a better definition of such regional suture, but also estimates on the long-controversial issue of net crustal growth in accretionary tectonic environments.
The results indicate short sedimentary transport distances between the arc basins and their provenances, of which the studied volcanic rocks were a major contributor. Similar enrichment and depletion patterns with respect to N-MORB and average continental crust further corroborate a close source-sediment relationship. Immobile element provenance analyses indicate that the active continental northern margin of the North China Craton was a major source for arc basins to the south of the Solonker Suture Zone. To its north, arc basins are interpreted to be sourced by a more complex mixture of provenances, e.g., the Baolidao volcanic arc suite and the heterogenous Precambrian basement of southern Mongolia. An overall collisional tectonic setting across the suture is recognised. The geochemical signature of sedimentary rocks to the south of the suture points at an active continental arc setting, whereas the bimodal geochemical distribution of the samples to the north show a contemporaneous active oceanic island arc as well as passive margin environment. These features favour a double-sided subduction of the Palaeo-Asian Ocean beneath the North China Craton and the Mongolian Arcs throughout the Palaeozoic, including back-arc basin opening north of the suture in the Permian.
Analysis of Hf and Nd isotopic compositions revealed that magmas to the south were produced involving significant crustal contamination, thus having less radiogenic compositions. North of the suture, however, isotopic compositions tend to be more radiogenic, implying a more juvenile contribution. However, the bulk isotopic compositions are close to present-day CHUR, suggesting that crustal reworking appears to be equally balanced by juvenile addition during the Palaeozoic closure of the Palaeo-Asian Ocean across the Solonker Suture Zone.
There is a broad consensus that the Solonker Suture Zone marks the final closure of the Paleo-Asi... more There is a broad consensus that the Solonker Suture Zone marks the final closure of the Paleo-Asian Ocean, which led to the formation of the eastern segment of the Central Asian Orogenic Belt. However, when and how the final closure occurred still remains controversial. To address this issue, provenance analysis of Permian sedimentary rocks of arc basins along the Xar Moron River was carried out. Geochemical analysis revealed a close relationship between the sedimentary and volcanic rock suite in the study region suggesting short transport distances and a complex convergent arc setting. Detrital zircon U-Pb analysis identified two major age provenances: (1) the Precambrian basement of the North China Craton (~2497 Ma and ~1844 Ma) and (2) the Paleozoic Southern Accretionary Orogen along the northern margin of North China (~436 Ma and ~269 Ma). The present locations of identified age provenances indicate southward subduction beneath the northern margin of North China. A comparison of the youngest age population in the sedimentary rocks with U-Pb ages obtained for subduction-related volcanic rocks implies that the Solonker Suture Zone formed from the Late Permian to Early Triassic. The results of our study advocate a complex Permian arc system which was probably similar to present-day Southeast Asia.
A detrital zircon U-Pb and Lu-Hf isotopic study was carried out on the Middle Silurian to Late Ca... more A detrital zircon U-Pb and Lu-Hf isotopic study was carried out on the Middle Silurian to Late Carboniferous sedimentary strata of the northwestern Tarim Craton in order to understand accretionary processes in the southern part of the Central Asian Orogenic Belt. Detrital zircons from these strata yielded U-Pb ages clustering around 2.8-2.3 Ga, 2.0-1.7 Ga, 1.3-0.9 Ga, 880-660 Ma and 500-400 Ma, with age populations and Hf isotopic signatures matching those of magmatic rocks in the Tarim Craton and the Central Tianshan Block. Abundant 500-400 Ma detrital zircons most likely reflect deposition in a retro-arc foreland basin inboard of an Andean-type magmatic arc to the north, supporting the northern Tarim-Central Tianshan connection during Early Paleozoic time. The absence of 380-310 Ma zircon population in the Carboniferous siliciclastic rocks suggests that the Central Tianshan Block may have been separated from the Tarim Craton in the Early Devonian, caused by the inter-arc/back-arc opening of the South Tianshan Ocean. We propose an accretionary orogenic model switching from advancing to retreating mode during Paleozoic time in the southwestern part of the Paleo-Asian Ocean. This transition most likely occurred coevally with the rifting of Southeast Asian blocks from the northeastern margin of Gondwana.
The Jiaodong Terrane of the Eastern Shandong Complex in the Eastern Block of the North China Crat... more The Jiaodong Terrane of the Eastern Shandong Complex in the Eastern Block of the North China Craton (NCC) consists predominantly of Archean granitoid gneisses with minor supracrustal rock enclaves or lenses. This study presents new zircon LA-ICP-MS U–Pb and Lu–Hf isotopic data for these lithologies, which help to better understand the Archean crustal evolution of the Eastern Block of the NCC. Magmatic zircon U–Pb data reveal that zircons in the supracrustal rocks and granitoid gneisses were generated by multi-stage events at ~ 2.9 Ga, ~ 2.7 Ga and ~ 2.5 Ga. Metamorphic zircon U–Pb data obtained for these rocks show distinct metamorphic ages at ~ 2.50 and ~ 1.9–1.8 Ga, suggesting that the Jiaodong Terrane experienced a regional metamorphic event at the end of the Neoarchean and encountered reworking by a tectonothermal event that was associated with the formation of the Paleoproterozoic Jiao–Liao–Ji Belt. Magmatic zircons have variable εHf(t) values from − 5.5 to + 7.7 with model ages of 3.92–2.57 Ga, of which most εHf(t) values are positive with a predominant peak of model ages at 3.4–3.1 Ga and a subordinate peak at 2.8–2.7 Ga. These Hf features reveal major juvenile crustal growth stages with significant additions of older crustal materials at 3.4–3.1 Ga and 2.8–2.7 Ga, and a crustal reworking event with minor juvenile additions at ~ 2.5 Ga in the Jiaodong Terrane.
Apatite fission track dating of five samples from Cenozoic volcanic strata in the Nimu District i... more Apatite fission track dating of five samples from Cenozoic volcanic strata in the Nimu District in the southern Gangdese Terrane exhibits single population grain ages with a single mean age and associated central ages ranging from 6.8 ± 0.6 Ma to 9.7 ± 1.2 Ma. Mean track lengths are between 12.9 ± 1.7 µm and 14.2 ± 2.3 µm with a single peak characteristic of a single thermal event. The newly documented ages coincide well with the age of high sedimentation rates in the North Tibet Basin that resulted from a 9–5 Ma compressional event. Track length modeling allows three stages to be identified in the sample cooling. The first stage (12–8 Ma) records a period of relative stability with little, if any, cooling at temperatures of 120–110°C suggesting this region had low relief. The second stage (8–2 Ma) reflects rapid cooling with temperatures decreasing from ∼110°C to surface temperatures of ∼15°C. This stage can be related to far-field effects of the Himalayan collision, which probably generated the surface uplift and relief that defines the present-day Gangdese Mountains. The mean uplift rate of this period is estimated to be 1.41–0.95 mm/y with total uplift reaching ∼5900 m. The final stage is related to surface evolution since the Pliocene.
The geological attraction of the Heilongjiang Complex, extending along a suture zone between the ... more The geological attraction of the Heilongjiang Complex, extending along a suture zone between the Jiamusi and Songliao blocks in Northeast China, resides in excellent exposures of blueschists, which occur in association with granitic gneisses, marbles, meta-ultramafic rocks, greenschists, quartzites, muscovite–albite schists and two-mica schists from the complex. However, controversy has long surrounded the ages and tectonic settings of mafic protoliths of the blueschists from the complex. The lithological association and major and trace element compositions indicate that the ultramafic–mafic protoliths of the Yilan blueschists can be subdivided into the tholeiitic and alkali groups, both of which were derived from partial melting of garnet-facies peridotites, but at different degrees of melting. Magmatic zircons from a tholeiitic blueschist sample yield a 206Pb/238U age of 275 ± 2 Ma, interpreted as its protolithic age. The sample also contains large amounts of older inherited zircons up to 1200 Ma, which, together with the geochemical features of the sample, indicate that the tholeiitic basalts were generated in a continental rift. The further development of the rift led to the formation of an ocean between the Jiamusi and Songliao blocks, in which some ocean islands developed, represented by the alkali mafic protoliths of the Yilan blueschists, as supported by geochemical data. Magmatic zircons from an alkaline mafic blueschist sample yield a 206Pb/238U age of 141.8 ± 1 Ma, indicating that the ocean between the Jiamusi and Songliao blocks had not been closed by ~ 141 Ma, not at 210–180 Ma as previously considered.
Geologie des Betancuria Massivs auf Fuerteventura, Kanarische Inseln: Eine geologische Geländeuntersuchung des plutonischen Basalkomplexes und ... nördlich von Pájara (German Edition)
Die Kanarischen Inseln gehören zusammen mit den Azoren, Madeira, Selvagens und Kapverden zu den m... more Die Kanarischen Inseln gehören zusammen mit den Azoren, Madeira, Selvagens und Kapverden zu den mittelatlantischen Vulkaninseln. Der vorwiegend vulkanische Aufbau der Kanaren erfolgte im Wesentlichen in drei Phasen: der sogenannten Prä-Schild-Phase, gefolgt von der Schild-Phase und abschließend der Post-Schild-Phase. Während auf den meisten Inseln jüngerer Magmatismus bis heute dominiert (rezent submarin nahe El Hierro), zeichent sich Fuerteventura zusätzlich durch die geologische Archivierung des ältesten aktiven Vulkanismus vor mehr als 65 Millionen Jahren aus. Dies formte den um die Ortschaft Pájara aufgeschlossenen Basalkomplex. Die hier vorgelegte Arbeit umfasst eine detaillierte geologische Geländeuntersuchung einschließlich geologischer Kartierung innerhalb dieses Basalkomplexes. Sie eignet sich als Basis für weitere geologische Untersuchungen, aber auch als geologischer Führer für den interessierten Laien.