title: The third-order law for magnetohydrodynamic turbulence with shear: Numerical investigation

authors: Wan, Minping

subjects: numerical analysis

abstract: The scaling laws of third-order structure functions for isotropic, homogeneous, and incompressible magnetohydrodynamic (MHD) turbulence relate the observable structure function with the energy dissipation rate. Recently [ Wan et al. Phys. Plasmas 16, 090703 (2009) ], the theory was extended to the case in which a constant velocity shear is present, motivated by the application of the third-order law to the solar wind. We use direct numerical simulations of two-dimensional MHD with shear to confirm this new generalization of the theory. The presence of the shear effect broadens the circumstances in which the law can be applied. Important implications for laboratory and space plasmas are discussed.

text: The third-order law for magnetohydrodynamic turbulence with shear: Numerical investigation The scaling laws of third-order structure functions for isotropic, homogeneous, and incompressible magnetohydrodynamic (MHD) turbulence relate the observable structure function with the energy dissipation rate. Recently [ Wan et al. Phys. Plasmas 16, 090703 (2009) ], the theory was extended to the case in which a constant velocity shear is present, motivated by the application of the third-order law to the solar wind. We use direct numerical simulations of two-dimensional MHD with shear to confirm this new generalization of the theory. The presence of the shear effect broadens the circumstances in which the law can be applied. Important implications for laboratory and space plasmas are discussed.

year: 2010

title: Multi-system geochronological and isotopic constraints on age and evolution of the Gaoligongshan metamorphic belt and shear zone system in western Yunnan, China

authors: Eroğlu, Sümeyya

subjects: Gaoligongshan

abstract: The Gaoligongshan metamorphic belt, located east of the Eastern Himalayan Syntaxis (EHS) in the Yunnan province, southwestern China, is a compelling region in which to determine temporal constrains on crustal dynamic processes related to the Himalayan orogeny. We applied multi-system geo- and thermochronology (900 °C to <50 °C) to orthogneiss and mylonites from a major shear zone in the southern Gaoligongshan in order to elucidate the magmatic, cooling and exhumation history of this belt.
Zircon U/Pb data reveal three magmatic events at ∼486 Ma, ∼136 Ma and ∼76 Ma. Similar ages are found in orthoderivative rocks of the neighboring Tengchong and Baoshan blocks, and the Gangdese batholith, suggesting that the southern Gaoligongshan is composed of an assemblage of Lhasa and Qiangtang terrane derived rocks. Muscovite Rb/Sr ages of 35–21 Ma are coeval with the onset of lateral crustal displacement along major shear zones in Eastern Tibet and Indochina, and with the post-collision volcanic activity in western Yunnan. Biotite Rb/Sr and mica 40Ar/39Ar ages provide evidence that mylonitization along the Gaoligongshan shear zone and crustal rotation of the Tengchong and Baoshan blocks proceeded during the Miocene, between 19 and 12 Ma, when the rocks rapidly cooled through the 350–280 °C temperature range. Almost identical 40Ar/39Ar ages reported for the Karakorum–Jiali–Parlung Fault system in Western Tibet suggest that the Gaoligongshan shear zone is the southeastern continuation of this fault, recording the eastward extrusion of Tibet and crustal movement around the EHS. The final stage of exhumation of the Gaoligongshan occurred between 8 and 5 Ma at an average exhumation rate of ∼3 km/Ma as documented by apatite fission-track and apatite (U–Th–Sm)/He data. This rapid exhumation was triggered by crustal root delamination and opening of the Andaman sea.
Our results clearly show that the complex tectonothermal evolution of the Gaoligongshan was influenced by Tibetan extrusion and escape tectonics associated with lower crustal flow around the EHS and the southeastward movement of Indochina and back-arc extension in response to Andaman seafloor spreading.

text: Multi-system geochronological and isotopic constraints on age and evolution of the Gaoligongshan metamorphic belt and shear zone system in western Yunnan, China The Gaoligongshan metamorphic belt, located east of the Eastern Himalayan Syntaxis (EHS) in the Yunnan province, southwestern China, is a compelling region in which to determine temporal constrains on crustal dynamic processes related to the Himalayan orogeny. We applied multi-system geo- and thermochronology (900 °C to <50 °C) to orthogneiss and mylonites from a major shear zone in the southern Gaoligongshan in order to elucidate the magmatic, cooling and exhumation history of this belt.
Zircon U/Pb data reveal three magmatic events at ∼486 Ma, ∼136 Ma and ∼76 Ma. Similar ages are found in orthoderivative rocks of the neighboring Tengchong and Baoshan blocks, and the Gangdese batholith, suggesting that the southern Gaoligongshan is composed of an assemblage of Lhasa and Qiangtang terrane derived rocks. Muscovite Rb/Sr ages of 35–21 Ma are coeval with the onset of lateral crustal displacement along major shear zones in Eastern Tibet and Indochina, and with the post-collision volcanic activity in western Yunnan. Biotite Rb/Sr and mica 40Ar/39Ar ages provide evidence that mylonitization along the Gaoligongshan shear zone and crustal rotation of the Tengchong and Baoshan blocks proceeded during the Miocene, between 19 and 12 Ma, when the rocks rapidly cooled through the 350–280 °C temperature range. Almost identical 40Ar/39Ar ages reported for the Karakorum–Jiali–Parlung Fault system in Western Tibet suggest that the Gaoligongshan shear zone is the southeastern continuation of this fault, recording the eastward extrusion of Tibet and crustal movement around the EHS. The final stage of exhumation of the Gaoligongshan occurred between 8 and 5 Ma at an average exhumation rate of ∼3 km/Ma as documented by apatite fission-track and apatite (U–Th–Sm)/He data. This rapid exhumation was triggered by crustal root delamination and opening of the Andaman sea.
Our results clearly show that the complex tectonothermal evolution of the Gaoligongshan was influenced by Tibetan extrusion and escape tectonics associated with lower crustal flow around the EHS and the southeastward movement of Indochina and back-arc extension in response to Andaman seafloor spreading.

year: 2013

title: The Aroha block to 1879

authors: Hart, Philip

abstract: Te Aroha was valued by Maori because of its strategic position as well as its healing hot springs, while Pakeha anticipated acquiring a large area (which shrank in size once surveyed) of fertile farming land. Before the Crown could acquire the block, the ownership of a disputed area fought over by the Marutuahu tribes (especially Ngati Maru) and Ngati Haua had to be determined. After the battle of Taumatawiwi of 1830, claimed as a victory by both sides, subsequent smaller battles continued for some years. In place of deciding ownership on this basis, the new land court struggled to make a judgment on the basis of  contradictory claims about ancestry, battles large and small, and occupation.
One part of the larger Aroha block, Ruakaka, was considered separately in 1869, resulting in the court allocating it to Ngati Haua. Also in that year, the first hearing of the Aroha Block was held, at Matamata, with the same outcome. Because of Maratuahu anger and threats of violence, Ngati Haua failed to survey the land as required, and a second hearing was held in Auckland, in 1871, at which Ngati Maru triumphed. Subsequently the block was occupied, but conflicts continued, notably when Ngati Haua gave a Pakeha permission to run cattle at Waiharakeke, further upriver. 
Starting in 1873, James Mackay slowly purchased the interests of individuals claiming ownership of the block, and paid off the Ngati Haua claimants. Then in December 1876, Ngati Tumutumu/Ngati Rahiri claimed the land for themselves, and in the following year the ownership of the Waitoki block, downstream from Te Aroha, was contested. In July 1878, a third hearing of the Aroha case commenced, resulting in Ngati Rahiri being allocated £3,000 and 7,500 acres, the remainder of the block going to Ngati Maru. Subsequently, the process of subdividing the owners’ interests proceeded, very slowly, and a small number of Pakeha settled and commenced farming or storekeeping.

text: The Aroha block to 1879 Te Aroha was valued by Maori because of its strategic position as well as its healing hot springs, while Pakeha anticipated acquiring a large area (which shrank in size once surveyed) of fertile farming land. Before the Crown could acquire the block, the ownership of a disputed area fought over by the Marutuahu tribes (especially Ngati Maru) and Ngati Haua had to be determined. After the battle of Taumatawiwi of 1830, claimed as a victory by both sides, subsequent smaller battles continued for some years. In place of deciding ownership on this basis, the new land court struggled to make a judgment on the basis of  contradictory claims about ancestry, battles large and small, and occupation.
One part of the larger Aroha block, Ruakaka, was considered separately in 1869, resulting in the court allocating it to Ngati Haua. Also in that year, the first hearing of the Aroha Block was held, at Matamata, with the same outcome. Because of Maratuahu anger and threats of violence, Ngati Haua failed to survey the land as required, and a second hearing was held in Auckland, in 1871, at which Ngati Maru triumphed. Subsequently the block was occupied, but conflicts continued, notably when Ngati Haua gave a Pakeha permission to run cattle at Waiharakeke, further upriver. 
Starting in 1873, James Mackay slowly purchased the interests of individuals claiming ownership of the block, and paid off the Ngati Haua claimants. Then in December 1876, Ngati Tumutumu/Ngati Rahiri claimed the land for themselves, and in the following year the ownership of the Waitoki block, downstream from Te Aroha, was contested. In July 1878, a third hearing of the Aroha case commenced, resulting in Ngati Rahiri being allocated £3,000 and 7,500 acres, the remainder of the block going to Ngati Maru. Subsequently, the process of subdividing the owners’ interests proceeded, very slowly, and a small number of Pakeha settled and commenced farming or storekeeping.

year: 2016