Constitutional Law - Search and Seizure - Brief Investigational Stops - Drug Courier Profiles

The United States Supreme Court has held that drug courier profiles may be utilized by law enforcement agents to demonstrate that a reasonable suspicion of criminal activity exists in order to justify their brief investigative stop of an individual for questioning within Constitutional parameters. United States v. Sokolow, _ U.S. -, 109 S. Ct. 1581 (1989)

K-metasomatism and the origin of Ba- and inclusion-zoned orthoclase megacrysts in the Papoose Flat pluton, Inyo Mountains, California, USA

In the Papoose Flat pluton in the Inyo Mountains of California the orthoclase megacrysts are suggested to form by K-metasomatism because microfracturing of a few normally zoned plagioclase crystals channeled introduced K-bearing fluids to these places, thereby promoting K-metasomatism and localized growth to form the megacrysts. Isochemical recrystallization to produce the megacrysts from preexisting stressed orthoclase and plagioclase crystals is ruled out because the original relatively undeformed granodiorite of the Papoose Flat pluton contained only 8-13 vol. % orthoclase that could not have been reorganized into more than 19 vol. % orthoclase in the groundmass and megacrysts and because original biotite was insufficient to supply enough K. An outside K source is required. Si-metasomatism of biotite to form quartz would have supplied some of the K. Concentrically oriented plagioclase inclusions that occur parallel to Ba-K growth zones in the megacrysts are shown to be formed from primary groundmass minerals, some of which were broken into fragments but others were not microfractured. The occurrences of myrmekite inside the megacrysts, scalloped edges on all surfaces of many plagioclase inclusions, sodic rims on irregular plagioclase inclusions against outer surfaces of former faces of the orthoclase, and disoriented inclusions that are not parallel to growth zones provide evidence for the primary origin of the inclusions. Rare trails of inclusions through the megacrysts indicate that the megacrysts are porphyroblasts and not residual phenocrysts (porphyroclasts). Microcline replacements of plagioclase which occur at lower temperature in cataclastically deformed granite (micro-aplites) produce abundant myrmekite and recrystallized sodic plagioclase. Pseudo-aplites in strongly sheared zones result where nearly all plagioclase is replaced by microcline, and most biotite is replaced by quartz. Progressive non-isochemical K-metasomatism occurred in the pluton with increasing deformation from the initial orthoclase appearance through the megacryst stage and then the final production of\ud microcline. Orthoclase megacrysts in the wall rock Campito sandstone are shown\ud to have a metasomatic origin similar to that found in the Papoose Flat pluton

A possible unsuspected significance of isotopic Rb-Sr "errorchrons"

Rb-Sr isotopic data that produce "errorchrons" with large ?? error values are commonly not published because more accurate dates calculated from isochrons are sought. An assumption is generally made that Sr is the only element that has moved out of the system when an errorchron is produced, but little work has been done to verify this hypothesis. A Rb-Sr errorchron occurs when data are plotted from chemically analyzed samples collected in the Kernville diorite-gabbro, north of the Lake Isabella Reservoir in the southern Sierra Nevada. Detailed structural, mineralogical, chemical, and Rb-Sr isotopic examinations of aplite-pegmatite-migmatite dikes and their transitions to Kernville diorite north of Lake, show how data that produce a Rb-Sr errorchron are generated. The changes in mineralogy and whole-rock major- and trace-element compositions in the modified transition rocks reveal different movements of both Rb and Sr isotopes as well as other trace elements and major oxides. On that basis, other terranes producing Rb-Sr isotopic data that plot as an errorchron should be examined carefully to see if major changes in mineralogy and chemistry are associated with processes that created the errorchron

K-metasomatism of plagioclase to produce microcline megacrysts in the Cathedral Peak granodiorite, Sierra Nevada, California, USA

Higgins (1999) proposed that microcline megacrysts in the Cathedral Peak granodiorite resulted from Ostwald ripening in which textural coarsening of earlier formed small K-feldspar crystals were sacrificed to feed the growth of a select few larger crystals. Textural evidence shows that Ostwald ripening did not occur, but, instead, the megacrysts resulted from K-replacement of broken plagioclase crystals in sites of strong cataclasis, where tiny microcline crystals (1 to 15 mm in mean height) grew to as much as 80 mm. The progressive growth of the microcline encompassed broken remnant fragments of ground mass minerals in concentric shells. The evidence for K-replacement consists of veins of microcline penetrating cores of broken zoned plagioclase, the alignment of one plane of the grid-twinning in the microcline with albite twinning in the plagioclase, the occurrence of myrmekite, and the replacement of biotite by quartz to provide the needed K