The Ramona pegmatite district of central San Diego County, California, has been known as a source of gem garnet, tourmaline, and topaz since the early 1900's. All the occurrences of known commercial importance lie within an area of about 1.5 square miles. The dominant rocks of the district are tonalites and granodiorites of the Cretaceous south...

The Ramona pegmatite district of central San Diego County, California, has been known as a source of gem garnet, tourmaline, and topaz since the early 1900's. All the occurrences of known commercial importance lie within an area of about 1.5 square miles. The dominant rocks of the district are tonalites and granodiorites of the Cretaceous south...

The Ramona pegmatite district of central San Diego County, California, has been known as a source of gem garnet, tourmaline, and topaz since the early 1900's. All the occurrences of known commercial importance lie within an area of about 1.5 square miles. The dominant rocks of the district are tonalites and granodiorites of the Cretaceous south...

The Ramona pegmatite district of central San Diego County, California, has been known as a source of gem garnet, tourmaline, and topaz since the early 1900's. All the occurrences of known commercial importance lie within an area of about 1.5 square miles. The dominant rocks of the district are tonalites and granodiorites of the Cretaceous south...

The greater Sierra Nevada batholith (SNB) is an ~ 600 km long NNW-trending composite arc assemblage consisting of a myriad of plutons exhibiting a distinct transverse zonation in structural, petrologic, geochronologic, and isotopic patterns. However, south of 35.5 °N: 1) the depth of exposure increases markedly; 2) primary zonation patterns swi...

The greater Sierra Nevada batholith (SNB) is an ~ 600 km long NNW-trending composite arc assemblage consisting of a myriad of plutons exhibiting a distinct transverse zonation in structural, petrologic, geochronologic, and isotopic patterns. However, south of 35.5 °N: 1) the depth of exposure increases markedly; 2) primary zonation patterns swi...

The greater Sierra Nevada batholith (SNB) is an ~ 600 km long NNW-trending composite arc assemblage consisting of a myriad of plutons exhibiting a distinct transverse zonation in structural, petrologic, geochronologic, and isotopic patterns. However, south of 35.5 °N: 1) the depth of exposure increases markedly; 2) primary zonation patterns swi...

The greater Sierra Nevada batholith (SNB) is an ~ 600 km long NNW-trending composite arc assemblage consisting of a myriad of plutons exhibiting a distinct transverse zonation in structural, petrologic, geochronologic, and isotopic patterns. However, south of 35.5 °N: 1) the depth of exposure increases markedly; 2) primary zonation patterns swi...