Wright (2004) experimented with Kulong lake water under normal surface temperature and pressure conditions to precipitate dolomites. His study offered experimental petrological evidence for primary dolomite formation. However, examples of ancient primary dolomites are rare.
a) This is a field photograph of steeply-dipping laminated dolostones sandwiched by weathered black laminites in Yuejingou. The hammer is 30 cm long. Stratigraphic-up is to the left (south). b) This is a photograph of a core containing intact interlaminated white and black laminites. c) This is a photograph of a core showing soft-sediment deformation, wavy lamination, and sharp and erosional bases of white and black laminites. Credit: ©Science China Press
A research group lead by Professor Liu at Northwestern University discovered primary dolostone formed by mantle-originated exhalative hydrothermal activities in an intracontinental rift basin in the Permian, analogous to "white smokers" on the modern seafloor. Their study offered important evidence of primary dolomite formation in geological history. See the paper entitled "Primary dolostone formation related to mantle-originated exhalative hydrothermal activities, Permian Yuejingou section, Santanghu area, Xinjiang, NW China" in Science China: Earth Sciences (No. 2, 2012).
In samples taken from the Yuejingou section and drill cores taken from the Santanghu Basin, the dolostone in the Permian Lucaogou Formation includes laminated dolomicrite (0.005-0.01 mm in size) and doloarenite (0.01-0.05 mm in size, such as K-feldspar analcime dolostone, dolomitic K-feldspar analcime laminite, microcrystalline quartz analcime laminite, and algal dolostone). They are finely (0.05-0.15 cm thick) interlaminated with lime micrite and dusty pyrite laminae that may be a product of black smokers. The interlaminites are probably the products of alternating hydrothermal exhalation of "black and white smokers" in the Santanghu lake. Alkali feldspar and analcime grains in dolostone are interpreted as having been derived from analcime phonolites and peralkaline igneous rocks.
Some analcime grains have a tetragonal trisoctahedron crystal form with embayed edges. Alkali feldspars are dominantly sanidine and orthoclase; and orthoclase commonly encases sanidine, which, in turn, is encased by analcime. The sequence reflects sequential crystallization of peralkaline magmas. The fragments of these rocks were brought up from the subsurface by hydrothermal fluid flows. These observations suggest that the lake was sediment-starved; lake water had a high temperature. Cathodoluminescence microscopy shows that the formation of ankerite and dolomite is earlier than that of calcite; ankerite and dolomite do not coexist, suggesting variable iron content in hydrothermal fluids.The 87Sr/86Sr ratios of 10 dolostones are 0.70457-0.706194, and 0.705005 on average, which are similar to the global average (0.70350). All doloarenite samples have a significantly negative äEu anomaly and a very weak positive äCe anomaly.
Jiao Xin | EurekAlert!
Sediment from Himalayas may have made 2004 Indian Ocean earthquake more severe
26.05.2017 | Oregon State University
Devils Hole: Ancient Traces of Climate History
24.05.2017 | Universität Innsbruck
Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.
Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....
Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.
The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
24.05.2017 | Event News
23.05.2017 | Event News
22.05.2017 | Event News
26.05.2017 | Life Sciences
26.05.2017 | Life Sciences
26.05.2017 | Physics and Astronomy